Polymers

1775 KiB

Open AccessArticle

Application of Chitinous Materials in Production and Purification of a Poly(l-lactic acid) Depolymerase from Pseudomonas tamsuii TKU015

by Tzu-Wen Liang, Shan-Ni Jen, Anh Dzung Nguyen and San-Lang Wang

Polymers 2016, 8(3), 98; https://doi.org/10.3390/polym8030098 - 22 Mar 2016

Cited by 30 | Viewed by 6621

Abstract

The management of fishery residues and plastics is considered to be a vital strategy for conserving resources and maintaining the quality of the environment. Poly(l-lactic acid) (PLA) is a commercially promising, renewable, and biodegradable plastic. In this study, a PLA depolymerase [...] Read more.

The management of fishery residues and plastics is considered to be a vital strategy for conserving resources and maintaining the quality of the environment. Poly(l-lactic acid) (PLA) is a commercially promising, renewable, and biodegradable plastic. In this study, a PLA depolymerase was produced in a squid pen powder (SPP) and recycled plastic waste (PLA powder)-containing medium by Pseudomonas tamsuii TKU015, a bacterial strain isolated from Taiwanese soil. This PLA depolymerase had a molecular weight of 58 kDa and was purified to homogeneity from the supernatant of a TKU015 culture. The optimum pH of TKU015 PLA depolymerase is 10, and the optimal temperature of the enzyme is 60 °C. In addition to PLA, TKU015 PLA depolymerase degraded fibrinogen and tributyrin, but did not hydrolyze casein, triolein, and poly(?-hydroxybutyrate). Taken together, these data demonstrate that P. tamsuii TKU015 produces a PLA depolymerase to utilize SPP and polylactide as carbon/nitrogen sources. Full article

(This article belongs to the Special Issue Biodegradable Polymers)

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Effects of MPS concentration (a) and culture temperature (b) on cell growth (dashed line) and PLA depolymerase activity (solid line) of P. tamsuii TKU015. All data points are means ± S.D. (standard deviation) of three different experiments performed on different days (each experiment was conducted in triplicate). Full article ">Figure 2
Elution profile of TKU015 PLA depolymerase from DEAE-Sepharose CL-6B. Full article ">Figure 3
Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE) analysis of PLA depolymerase produced by P. tamsuii TKU015. Lanes: M, molecular markers (170, 130, 95, 72, 55, 43, 34, and 26 kDa); (1) crude enzyme; (2) adsorbed PLA depolymerase fractions after DEAE-Sepharose CL-6B chromatography; (3) adsorbed PLA depolymerase fractions after Macro-prep DEAE chromatography; (4) PLA depolymerase fractions after Sephacryl S-100. Full article ">Figure 4
Effects of pH and temperature on the activity and stability of the PLA depolymerase from P. tamsuii TKU015. (a) Optimum pH; (b) pH stability; (c) optimum temperature; (d) thermal stability. All data points are means ± S.D. of three different experiments performed on different days (each experiment was conducted in triplicate). Means with different letters are significantly different at p < 0.05. Full article ">Figure 4 Cont.
Effects of pH and temperature on the activity and stability of the PLA depolymerase from P. tamsuii TKU015. (a) Optimum pH; (b) pH stability; (c) optimum temperature; (d) thermal stability. All data points are means ± S.D. of three different experiments performed on different days (each experiment was conducted in triplicate). Means with different letters are significantly different at p < 0.05. Full article ">

5235 KiB

Open AccessArticle

Influence of Electrospinning Parameters on Fiber Diameter and Mechanical Properties of Poly(3-Hydroxybutyrate) (PHB) and Polyanilines (PANI) Blends

by Ahmed M. El-hadi and Fatma Y. Al-Jabri

Polymers 2016, 8(3), 97; https://doi.org/10.3390/polym8030097 - 22 Mar 2016

Cited by 43 | Viewed by 8071

Abstract

Random and oriented fibers of poly (3-hydroxybutyrate) (PHB) and their blends were manufactured using electrospinning using a co-solvent. The kind and the concentration of the co-solvent affected the diameter of electrospun fibers. The morphology, thermal analysis, and crystalline structure of electrospun fibers was [...] Read more.

Random and oriented fibers of poly (3-hydroxybutyrate) (PHB) and their blends were manufactured using electrospinning using a co-solvent. The kind and the concentration of the co-solvent affected the diameter of electrospun fibers. The morphology, thermal analysis, and crystalline structure of electrospun fibers was studied using polarized optical microscop (POM), Differential scanning colametry (DSC), Scanning Electron Microscopy (SEM), Wide angle X-ray diffraction (WAXD), and FT-IR analysis. The diameter of the electrospun fibers decreases with increasing collector speed for the blends compared to pure PHB, which are about 6 µm in diameter. The fibers obtained from blends reduce to 2 µm. The aligned electrospun fiber mats obtained from pure PHB showed no signs of necking at different take-up speeds, but the blends show multiple necking. It was found by FT-IR that the peak intensity at 1379 cm^?1 was lower by take up speed than in casting films; this peak is sensitive to crystallinity of PHB. The addition of polyanilines (PANIs) to (PHB) with a plasticizer decreases the diameter of the electrospun fiber. Full article

(This article belongs to the Special Issue Biodegradable Polymers)

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4895 KiB

Open AccessFeature PaperArticle

Water-Dispersible Silica-Polyelectrolyte Nanocomposites Prepared via Acid-Triggered Polycondensation of Silicic Acid and Directed by Polycations

by Philip Overton, Elena Danilovtseva, Erno Karjalainen, Mikko Karesoja, Vadim Annenkov, Heikki Tenhu and Vladimir Aseyev

Polymers 2016, 8(3), 96; https://doi.org/10.3390/polym8030096 - 22 Mar 2016

Cited by 7 | Viewed by 11918

Abstract

The present work describes the acid-triggered condensation of silicic acid, Si(OH)₄, as directed by selected polycations in aqueous solution in the pH range of 6.5–8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the [...] Read more.

The present work describes the acid-triggered condensation of silicic acid, Si(OH)₄, as directed by selected polycations in aqueous solution in the pH range of 6.5–8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the formation of silica-polyelectrolyte (S-PE) nanocomposites in the form of precipitate or water-dispersible particles. The mean hydrodynamic diameter (d_h) of size distributions of the prepared water-dispersible S-PE composites is presented as a function of the solution pH at which the composite formation was achieved. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and block copolymers of DMAEMA and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) were used as weak polyelectrolytes in S-PE composite formation. The activity of the strong polyelectrolytes poly(methacryloxyethyl trimethylammonium iodide) (PMOTAI) and PMOTAI-b-POEGMA in S-PE formation is also examined. The effect of polyelectrolyte strength and the OEGMA block on the formation of the S-PE composites is assessed with respect to the S-PE composites prepared using the PDMAEMA homopolymer. In the presence of the PDMAEMA₆₀ homopolymer (M_w = 9400 g/mol), the size of the dispersible S-PE composites increases with solution pH in the range pH 6.6–8.1, from d_h = 30 nm to d_h = 800 nm. S-PDMAEMA₆₀ prepared at pH 7.8 contained 66% silica by mass (TGA). The increase in dispersible S-PE particle size is diminished when directed by PDMAEMA₃₀₀ (M_w = 47,000 g/mol), reaching a maximum of d_h = 75 nm. S-PE composites formed using PDMAEMA-b-POEGMA remain in the range d_h = 20–30 nm across this same pH regime. Precipitated S-PE composites were obtained as spheres of up to 200 nm in diameter (SEM) and up to 65% mass content of silica (TGA). The conditions of pH for the preparation of dispersible and precipitate S-PE nanocomposites, as directed by the five selected polyelectrolytes PDMAEMA₆₀, PDMAEMA₃₀₀, PMOTAI₆₀, PDMAEMA₆₀-b-POEGMA₃₈ and PMOTAI₆₀-b-POEGMA₃₈ is summarized. Full article

(This article belongs to the Special Issue Polymers for Aqueous Media)

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10462 KiB

Open AccessFeature PaperArticle

Multilayer Graphene/Carbon Black/Chlorine Isobutyl Isoprene Rubber Nanocomposites

by Daniele Frasca, Dietmar Schulze, Volker Wachtendorf, Bernd Krafft, Thomas Rybak and Bernhard Schartel

Polymers 2016, 8(3), 95; https://doi.org/10.3390/polym8030095 - 22 Mar 2016

Cited by 30 | Viewed by 8798

Abstract

High loadings of carbon black (CB) are usually used to achieve the properties demanded of rubber compounds. In recent years, distinct nanoparticles have been investigated to replace CB in whole or in part, in order to reduce the necessary filler content or to [...] Read more.

High loadings of carbon black (CB) are usually used to achieve the properties demanded of rubber compounds. In recent years, distinct nanoparticles have been investigated to replace CB in whole or in part, in order to reduce the necessary filler content or to improve performance. Multilayer graphene (MLG) is a nanoparticle made of just 10 graphene sheets and has recently become commercially available for mass-product nanocomposites. Three phr (part for hundred rubbers) of MLG are added to chlorine isobutyl isoprene rubber (CIIR)/CB composites in order to replace part of the CB. The incorporation of just 3 phr MLG triples the Young’s modulus of CIIR; the same effect is obtained with 20 phr CB. The simultaneous presence of three MLG and CB also delivers remarkable properties, e.g. adding three MLG and 20 phr CB increased the hardness as much as adding 40 phr CB. A comprehensive study is presented, showing the influence on a variety of mechanical properties. The potential of the MLG/CB combination is illustrated to reduce the filler content or to boost performance, respectively. Apart from the remarkable mechanical properties, the CIIR/CB/MLG nanocomposites showed an increase in weathering resistance. Full article

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3893 KiB

Open AccessArticle

Mussel-Inspired Anisotropic Nanocellulose and Silver Nanoparticle Composite with Improved Mechanical Properties, Electrical Conductivity and Antibacterial Activity

by Hoang-Linh Nguyen, Yun Kee Jo, Minkyu Cha, Yun Jeong Cha, Dong Ki Yoon, Naresh D. Sanandiya, Ekavianty Prajatelistia, Dongyeop X. Oh and Dong Soo Hwang

Polymers 2016, 8(3), 102; https://doi.org/10.3390/polym8030102 - 22 Mar 2016

Cited by 61 | Viewed by 14394

Abstract

Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but [...] Read more.

Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but cellulose itself has neither antibacterial activity nor conductivity. Here, an antibacterial and electrically conductive composite was formed by generating catechol mediated silver nanoparticles (AgNPs) on the surface of cellulose nanofibers. The chemically immobilized catechol moiety on the nanofibrous cellulose network reduced Ag⁺ to form AgNPs on the cellulose nanofiber. The AgNPs cellulose composite showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria. In addition, the catechol conjugation and the addition of AgNP induced anisotropic self-alignment of the cellulose nanofibers which enhances electrical and mechanical properties of the composite. Therefore, the composite containing AgNPs and anisotropic aligned the cellulose nanofiber may be useful for biomedical applications. Full article

(This article belongs to the Special Issue Renewable Polymeric Adhesives)

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Full article ">Figure 1
Schematic figures of (A) the anisotropic carboxylated cellulose nanofibers (CCNF)-dopamine (DA)/silver nanoparticles (AgNPs) composite formation process; and (B) the antibacterial activity of CCNF-DA/AgNPs composite. Full article ">Figure 1 Cont.
Schematic figures of (A) the anisotropic carboxylated cellulose nanofibers (CCNF)-dopamine (DA)/silver nanoparticles (AgNPs) composite formation process; and (B) the antibacterial activity of CCNF-DA/AgNPs composite. Full article ">Figure 2
Morphological change of carboxylated cellulose nanofibers (CCNF) by conjugating catechol and silver nanoparticles. (A) TEM images of CCNF and (B) CCNF-DA/AgNPs; (C) polarized optical microscopy (POM) image of CCNF-DA with retardation (λ) plate; magenta and blue (or yellow) show disordered and anisotropic domains, respectively. The insect in (C) indicates the polarization directions of the polarizer (P) and analyzer (A); (D) SEM image of CCNF-DA. Full article ">Figure 3
(A) UV–Vis spectroscopy of supernatant from CCNF, CCNF-DA and CCNF films. The insect in (A) shows the supernatant from the CCNF-DA/AgNPs film; (B) high-resolution transmission electron microscopy (HRTEM) image of extracted AgNPs. The inset black box in (B) indicates the area where the enlarged HRTEM image (bottom-right panel) was taken; (C) selected area electron diffraction (SAED) pattern of silver crystal of CCNF-DA/AgNP. Full article ">Figure 4
(A) Stress-strain curve; (B) tensile strength; (C) toughness; and (D) Young’s modulus of CCNF, CCNF-DA, and CCNF-DA/AgNPs films. The data of quadruplicate samples represent mean ± standard deviation with statistical significance (* p < 0.05, ** p < 0.01, *** p < 0.005; unpaired t-test). Full article ">Figure 5
Antibacterial test on CCNF-DA/AgNPs membrane. (A) Disk diffusion test; (B) bacterial growth profiles; and (C) bactericidal profiles of the CCNF-DA/AgNPs membrane against E. coli; (D) Growth-inhibiting (left) and bactericidal (right) efficacies of CCNF-DA/AgNPs membrane for a long period. White arrows indicate the inhibition zone. The data represent mean ± standard deviation with statistical significance (* p < 0.05, ** p < 0.01, *** p < 0.005; unpaired t-test). Full article ">

4541 KiB

Open AccessArticle

Amphiphilic Fluorinated Block Copolymer Synthesized by RAFT Polymerization for Graphene Dispersions

by Hyang Moo Lee, Suguna Perumal and In Woo Cheong

Polymers 2016, 8(3), 101; https://doi.org/10.3390/polym8030101 - 22 Mar 2016

Cited by 16 | Viewed by 8680

Abstract

Despite the superior properties of graphene, the strong ?–? interactions among pristine graphenes yielding massive aggregation impede industrial applications. For non-covalent functionalization of highly-ordered pyrolytic graphite (HOPG), poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinyl pyridine) (PTFEMA-b-PVP) block copolymers were prepared by reversible addition-fragmentation chain [...] Read more.

Despite the superior properties of graphene, the strong ?–? interactions among pristine graphenes yielding massive aggregation impede industrial applications. For non-covalent functionalization of highly-ordered pyrolytic graphite (HOPG), poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinyl pyridine) (PTFEMA-b-PVP) block copolymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and used as polymeric dispersants in liquid phase exfoliation assisted by ultrasonication. The HOPG graphene concentrations were found to be 0.260–0.385 mg/mL in methanolic graphene dispersions stabilized with 10 wt % (relative to HOPG) PTFEMA-b-PVP block copolymers after one week. Raman and atomic force microscopy (AFM) analyses revealed that HOPG could not be completely exfoliated during the sonication. However, on-line turbidity results confirmed that the dispersion stability of HOPG in the presence of the block copolymer lasted for one week and that longer PTFEMA and PVP blocks led to better graphene dispersibility. Force–distance (F–d) analyses of AFM showed that PVP block is a good graphene-philic block while PTFEMA is methanol-philic. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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4563 KiB

Open AccessArticle

Rheological and Mechanical Behavior of Silk Fibroin Reinforced Waterborne Polyurethane

by Yongzhen Tao, Anwarul Hasan, George Deeb, Changkai Hu and Huipeng Han

Polymers 2016, 8(3), 94; https://doi.org/10.3390/polym8030094 - 21 Mar 2016

Cited by 23 | Viewed by 8008

Abstract

Waterborne polyurethane (WPU) is a versatile and environment-friendly material with growing applications in both industry and academia. Silk fibroin (SF) is an attractive material known for its structural, biological and hemocompatible properties. The SF reinforced waterborne polyurethane (WPU) is a promising scaffold material [...] Read more.

Waterborne polyurethane (WPU) is a versatile and environment-friendly material with growing applications in both industry and academia. Silk fibroin (SF) is an attractive material known for its structural, biological and hemocompatible properties. The SF reinforced waterborne polyurethane (WPU) is a promising scaffold material for tissue engineering applications. In this work, we report synthesis and characterization of a novel nanocomposite using SF reinforced WPU. The rheological behaviors of WPU and WPU-SF dispersions with different solid contents were investigated with steady shear and dynamic oscillatory tests to evaluate the formation of the cross-linked gel structure. The average particle size and the zeta potential of WPU-SF dispersions with different SF content were examined at 25 °C to investigate the interaction between SF and WPU. FTIR, SEM, TEM and tensile testing were performed to study the effects of SF content on the structural morphology and mechanical properties of the resultant composite films. Experimental results revealed formation of gel network in the WPU dispersions at solid contents more than 17 wt %. The conjugate reaction between the WPU and SF as well as the hydrogen bond between them helped in dispersing the SF powder into the WPU matrix as small aggregates. Addition of SF to the WPU also improved the Young’s modulus from 0.30 to 3.91 MPa, tensile strength from 0.56 to 8.94 MPa, and elongation at break from 1067% to 2480%, as SF was increased up to 5 wt %. Thus, significant strengthening and toughening can be achieved by introducing SF powder into the WPU formulations. Full article

(This article belongs to the Special Issue Polymers Applied in Tissue Engineering)

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2805 KiB

Open AccessArticle

Studies on Preparation of Poly(3,4-Dihydroxyphenylalanine)-Polylactide Copolymers and the Effect of the Structure of the Copolymers on Their Properties

by Dongjian Shi, Jiali Shen, Zenghui Zhao, Chang Shi and Mingqing Chen

Polymers 2016, 8(3), 92; https://doi.org/10.3390/polym8030092 - 18 Mar 2016

Cited by 9 | Viewed by 6450

Abstract

Properties of copolymers are generally influenced by the structure of the monomers and polymers. For the purpose of understanding the effect of polymer structure on the properties, two kinds of copolymers, poly(3,4-dihydroxyphenylalanine)-g-polylactide and poly(3,4-dihydroxyphenylalanine)-b-polylactide (PDOPA-g-PLA and PDOPA- [...] Read more.

Properties of copolymers are generally influenced by the structure of the monomers and polymers. For the purpose of understanding the effect of polymer structure on the properties, two kinds of copolymers, poly(3,4-dihydroxyphenylalanine)-g-polylactide and poly(3,4-dihydroxyphenylalanine)-b-polylactide (PDOPA-g-PLA and PDOPA-b-PLA) were designed and prepared by ring-opening polymerization of lactide with pre-prepared PDOPA as the initiator and the amidation of the functional PLA and PDOPA oligomer, respectively. The molecular weight and composition of the copolymers could be adjusted by changing the molar ratio of LA and DOPA and were confirmed by gel permeation chromatography (GPC) and proton nuclear magnetic resonance (¹H NMR) spectra. The obtained copolymers with graft and block structures showed high solubility even in common organic solvents. The effects of the graft and block structures on the thermal and degradation properties were also detected. The PDOPA-g-PLA copolymers showed higher thermal stability than the PDOPA-b-PLA copolymers, due to the PDOPA-g-PLA copolymers with regular structure and strong ?-? stacking interactions among the intermolecular and intramolecular chains. In addition, the degradation results showed that the PDOPA-g-PLA copolymers and the copolymers with higher DOPA composition had quicker degradation speeds. Interestingly, both two kinds of copolymers, after degradation, became undissolved in the organic solvents because of the oxidation and crosslinking formation of the catechol groups in the DOPA units during degradation in alkaline solution. Moreover, fluorescent microscopy results showed good biocompatibility of the PDOPA-g-PLA and PDOPA-b-PLA copolymers. The PDOPA and PLA copolymers have the potential applications to the biomedical and industrial fields. Full article

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7699 KiB

Open AccessArticle

Preparation of Uniform-Sized and Dual Stimuli-Responsive Microspheres of Poly(N-Isopropylacrylamide)/Poly(Acrylic acid) with Semi-IPN Structure by One-Step Method

by En-Ping Lai, Yu-Xia Wang, Yi Wei and Guang Li

Polymers 2016, 8(3), 90; https://doi.org/10.3390/polym8030090 - 17 Mar 2016

Cited by 29 | Viewed by 8966

Abstract

A novel strategy was developed to synthesize uniform semi-interpenetrating polymer network (semi-IPN) microspheres by premix membrane emulsification combined with one-step polymerization. Synthesized poly(acrylic acid) (PAAc) polymer chains were added prior to the inner water phase, which contained N-isopropylacrylamide (NIPAM) monomer, N, [...] Read more.

A novel strategy was developed to synthesize uniform semi-interpenetrating polymer network (semi-IPN) microspheres by premix membrane emulsification combined with one-step polymerization. Synthesized poly(acrylic acid) (PAAc) polymer chains were added prior to the inner water phase, which contained N-isopropylacrylamide (NIPAM) monomer, N,N?-methylene bisacrylamide (MBA) cross-linker, and ammonium persulfate (APS) initiator. The mixtures were pressed through a microporous membrane to form a uniform water-in-oil emulsion. By crosslinking the NIPAM in a PAAc-containing solution, microspheres with temperature- and pH-responsive properties were fabricated. The semi-IPN structure and morphology of the microspheres were confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average diameter of the obtained microspheres was approximately 6.5 ?m, with Span values of less than 1. Stimuli-responsive behaviors of the microspheres were studied by the cloud-point method. The results demonstrated that semi-IPN microspheres could respond independently to both pH and temperature changes. After storing in a PBS solution (pH 7.0) at 4 °C for 6 months, the semi-IPN microspheres remained stable without a change in morphology or particle size. This study demonstrated a promising method for controlling the synthesis of semi-IPN structure microspheres with a uniform size and multiple functionalities. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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41203 KiB

Open AccessFeature PaperReview

Decorating Nanoparticle Surface for Targeted Drug Delivery: Opportunities and Challenges

by Zhiqiang Shen, Mu-Ping Nieh and Ying Li

Polymers 2016, 8(3), 83; https://doi.org/10.3390/polym8030083 - 17 Mar 2016

Cited by 87 | Viewed by 16463

Abstract

The size, shape, stiffness (composition) and surface properties of nanoparticles (NPs) have been recognized as key design parameters for NP-mediated drug delivery platforms. Among them, the surface functionalization of NPs is of great significance for targeted drug delivery. For instance, targeting moieties are [...] Read more.

The size, shape, stiffness (composition) and surface properties of nanoparticles (NPs) have been recognized as key design parameters for NP-mediated drug delivery platforms. Among them, the surface functionalization of NPs is of great significance for targeted drug delivery. For instance, targeting moieties are covalently coated on the surface of NPs to improve their selectively and affinity to cancer cells. However, due to a broad range of possible choices of surface decorating molecules, it is difficult to choose the proper one for targeted functions. In this work, we will review several representative experimental and computational studies in selecting the proper surface functional groups. Experimental studies reveal that: (1) the NPs with surface decorated amphiphilic polymers can enter the cell interior through penetrating pathway; (2) the NPs with tunable stiffness and identical surface chemistry can be selectively accepted by the diseased cells according to their stiffness; and (3) the NPs grafted with pH-responsive polymers can be accepted or rejected by the cells due to the local pH environment. In addition, we show that computer simulations could be useful to understand the detailed physical mechanisms behind these phenomena and guide the design of next-generation NP-based drug carriers with high selectivity, affinity, and low toxicity. For example, the detailed free energy analysis and molecular dynamics simulation reveals that amphiphilic polymer-decorated NPs can penetrate into the cell membrane through the “snorkeling” mechanism, by maximizing the interaction energy between the hydrophobic ligands and lipid tails. We anticipate that this work will inspire future studies in the design of environment-responsive NPs for targeted drug delivery. Full article

(This article belongs to the Special Issue Computational Modeling and Simulation in Polymer)

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2899 KiB

Open AccessArticle

A Heterobimetallic Anionic 3,6-Connected 2D Coordination Polymer Based on Nitranilate as Ligand

by Samia Benmansour and Carlos J. Gómez-García

Polymers 2016, 8(3), 89; https://doi.org/10.3390/polym8030089 - 16 Mar 2016

Cited by 25 | Viewed by 6921

Abstract

In order to synthesize new coordination polymers with original architectures and interesting magnetic properties, we used the nitranilate ligand (C₆O₄(NO₂)₂^2? = C₆N₂O₈^2?), derived from the dianionic ligand dhbq [...] Read more.

In order to synthesize new coordination polymers with original architectures and interesting magnetic properties, we used the nitranilate ligand (C₆O₄(NO₂)₂^2? = C₆N₂O₈^2?), derived from the dianionic ligand dhbq^2? (2,5-dihydroxy-1,4-benzoquinone = H₂C₆O₄^2?). The use of this bis-bidentate bridging ligand led to [(DAMS)₂{FeNa(C₆N₂O₈)₃}·CH₃CN]_n (1) (DAMS⁺ = C₁₆H₁₇N₂⁺ = 4-[4-(dimethylamino)-?-styryl]-1-methylpyridinium), a 2D heterometallic coordination polymer presenting an unprecedented structure for any anilato-based compound. This structural type is a 3,6-connected 2D coordination polymer derived from the well-known honeycomb hexagonal structure, where Fe(III) ions alternate with Na⁺ dimers (as Na₂O₁₂ units) in the vertices of the hexagons and with an additional [Fe(C₆N₂O₈)₃]^3? anion located in the center of the hexagons connecting the three Na⁺ dimers. The magnetic properties of compound 1 show the presence of paramagnetic isolated high spin Fe(III) complexes with a zero field splitting, |D| = 8.5 cm^?1. Full article

(This article belongs to the Special Issue Coordination Polymers: New Materials for Multiple Applications)

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Full article ">Figure 1
Ortep views of the fragments of the structure of compound 1 with the labeling scheme: (a) structure of the [Fe(C6N2O8)3]3− unit; (b) structure of the Na2O12 dimer; (c) structure of the DAMS+ cation. Full article ">Figure 2
(a) View of the alternating cationic and anionic layers in compound 1. H atoms have been omitted for clarity; (b) View along the c direction of two consecutive cationic layers showing the different orientation of the DAMS+ molecules in each layer (yellow and red). The anionic intermediate layer is only represented by the Fe(III) and Na+ ions (orange and purple, respectively). Full article ">Figure 3
View of the 3,6-connected anionic layer [NaFe(C6N2O8)3]2− generated with Fe(III) and pairs of Na+ cations (the oxygen atoms of the NO2 groups have been omitted for clarity). Color code: Fe = orange, Na = purple, O = red, N = blue and C = grey. Full article ">Figure 4
Thermal variation of the χmT product per Fe(III) ion for compound 1. Solid line is the best fit to the model (see text). Full article ">Figure 5
Structures of (a) nitranilate ligand and (b) DAMS+ cation. Full article ">

2865 KiB

Open AccessArticle

Stability Study of Flexible 6,13-Bis(triisopropylsilylethynyl)pentacene Thin-Film Transistors with a Cross-Linked Poly(4-vinylphenol)/Yttrium Oxide Nanocomposite Gate Insulator

by Jin-Hyuk Kwon, Xue Zhang, Shang Hao Piao, Hyoung Jin Choi, Jin-Hyuk Bae and Jaehoon Park

Polymers 2016, 8(3), 88; https://doi.org/10.3390/polym8030088 - 16 Mar 2016

Cited by 14 | Viewed by 7638

Abstract

We investigated the electrical and mechanical stability of flexible 6,13-bis(triisopropylsilylehtynyl)pentacene (TIPS-pentacene) thin-film transistors (TFTs) that were fabricated on polyimide (PI) substrates using cross-linked poly(4-vinylphenol) (c-PVP) and c-PVP/yttrium oxide (Y₂O₃) nanocomposite films as gate insulators. Compared with the electrical characteristics [...] Read more.

We investigated the electrical and mechanical stability of flexible 6,13-bis(triisopropylsilylehtynyl)pentacene (TIPS-pentacene) thin-film transistors (TFTs) that were fabricated on polyimide (PI) substrates using cross-linked poly(4-vinylphenol) (c-PVP) and c-PVP/yttrium oxide (Y₂O₃) nanocomposite films as gate insulators. Compared with the electrical characteristics of TIPS-pentacene TFTs with c-PVP insulators, the TFTs with c-PVP/Y₂O₃ nanocomposite insulators exhibited enhancements in the drain current and the threshold voltage due to an increase in the dielectric capacitance. In electrical stability experiments, a gradual decrease in the drain current and a negative shift in the threshold voltage occurred during prolonged bias stress tests, but these characteristic variations were comparable for both types of TFT. On the other hand, the results of mechanical bending tests showed that the characteristic degradation of the TIPS-pentacene TFTs with c-PVP/Y₂O₃ nanocomposite insulators was more critical than that of the TFTs with c-PVP insulators. In this study, the detrimental effect of the nanocomposite insulator on the mechanical stability of flexible TIPS-pentacene TFTs was found to be caused by physical adhesion of TIPS-pentacene molecules onto the rough surfaces of the c-PVP/Y₂O₃ nanocomposite insulator. These results indicate that the dielectric and morphological properties of polymeric nanocomposite insulators are significant when considering practical applications of flexible electronics operated at low voltages. Full article

(This article belongs to the Collection Silicon-Containing Polymeric Materials)

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(a) TEM images of Y2O3 particles; (b) Schematic of the fabricated flexible TIPS-pentacene TFT. Full article ">Figure 2
Output characteristics of the flexible TIPS-pentacene TFTs with the (a) c-PVP/Y2O3 composite and (b) c-PVP gate insulators |ID| vs. VG and |ID|1/2 vs. VG plots of TIPS-pentacene TFTs with the (c) c-PVP/Y2O3 composite and (d) c-PVP gate insulators. Full article ">Figure 3
AFM images of the (a) c-PVP and (b) c-PVP/Y2O3 composite films. The insets show the contact angles on both films. AFM images of the TIPS-pentacene films deposited on the (c) c-PVP and (d) c-PVP/Y2O3 composite films. Full article ">Figure 4
Time-dependent decay behaviors of the (a) drain and (b) gate currents of the flexible TIPS-pentacene TFTs, during a prolonged bias stress test. Full article ">Figure 5
Leakage current paths through the (a) c-PVP/Y2O3 composite and (b) c-PVP gate insulators. (c) Possible interaction between the holes and the Y2O3 nanoparticles in the c-PVP/Y2O3 composite insulator. Full article ">Figure 6
Variations in the threshold voltages of the flexible TIPS-pentacene TFTs with the c-PVP/Y2O3 composite and c-PVP gate insulators, during a prolonged bias stress test. Full article ">Figure 7
(a) Variations in the drain current of the fabricated TFTs, induced by cyclic bending stresses. Transfer characteristics of the flexible TIPS-pentacene TFTs with the (b) c-PVP/Y2O3 composite and (c) c-PVP gate insulators, measured during cyclic bending stress tests. Full article ">

6132 KiB

Open AccessArticle

Charge Transport in LDPE Nanocomposites Part I—Experimental Approach

by Anh T. Hoang, Love Pallon, Dongming Liu, Yuriy V. Serdyuk, Stanislaw M. Gubanski and Ulf W. Gedde

Polymers 2016, 8(3), 87; https://doi.org/10.3390/polym8030087 - 16 Mar 2016

Cited by 62 | Viewed by 7587

Abstract

This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene and its nanocomposites filled with uncoated MgO and Al₂O₃, with the aim to highlight the effect of the nanofillers on charge transport processes. Material [...] Read more.

This work presents results of bulk conductivity and surface potential decay measurements on low-density polyethylene and its nanocomposites filled with uncoated MgO and Al₂O₃, with the aim to highlight the effect of the nanofillers on charge transport processes. Material samples at various filler contents, up to 9 wt %, were prepared in the form of thin films. The performed measurements show a significant impact of the nanofillers on reduction of material’s direct current (dc) conductivity. The investigations thus focused on the nanocomposites having the lowest dc conductivity. Various mechanisms of charge generation and transport in solids, including space charge limited current, Poole-Frenkel effect and Schottky injection, were utilized for examining the experimental results. The mobilities of charge carriers were deduced from the measured surface potential decay characteristics and were found to be at least two times lower for the nanocomposites. The temperature dependencies of the mobilities were compared for different materials. Full article

(This article belongs to the Special Issue Nano- and Microcomposites for Electrical Engineering Applications)

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4890 KiB

Open AccessArticle

Synthesis, Structures and Luminescence Properties of Metal-Organic Frameworks Based on Lithium-Lanthanide and Terephthalate

by Mohammed S. M. Abdelbaky, Zakariae Amghouz, Santiago García-Granda and José R. García

Polymers 2016, 8(3), 86; https://doi.org/10.3390/polym8030086 - 16 Mar 2016

Cited by 14 | Viewed by 8928

Abstract

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)₂(H₂O)·2(H₂O)] (MS1-6,7a) and [LiTb(BDC)₂] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y_0.96Eu_0.04, Y_0.93Tb_0.07, and [...] Read more.

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)₂(H₂O)·2(H₂O)] (MS1-6,7a) and [LiTb(BDC)₂] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y_0.96Eu_0.04, Y_0.93Tb_0.07, and H₂BDC = terephthalic acid), were obtained under hydrothermal conditions. The isostructural MS1-6 crystallize in monoclinic P2₁/c space group. While, in the case of Tb³⁺ a mixture of at least two phases was obtained, the former one (MS7a) and a new monoclinic C2/c phase (MS7b). All compounds have been studied by single-crystal and powder X-ray diffraction, thermal analyses (TGA), vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX). The structures of MS1-6 and MS7a are built up of inorganic-organic hybrid chains. These chains constructed from unusual four-membered rings, are formed by edge- and vertex-shared {LnO₈} and {LiO₄} polyhedra through oxygen atoms O3 (vertex) and O6-O7 (edge). Each chain is cross-linked to six neighboring chains through six terephthalate bridges. While, the structure of MS7b is constructed from double inorganic chains, and each chain is, in turn, related symmetrically to the adjacent one through the c glide plane. These chains are formed by infinitely alternating {LiO₄} and {TbO₈} polyhedra through (O2-O3) edges to create Tb–O–Li connectivity along the c-axis. Both MS1-6,7a and MS7b structures possess a 3D framework with 1D trigonal channels running along the a and c axes, containing water molecules and anhydrous, respectively. Topological studies revealed that MS1-6 and MS7a have a new 2-nodal 3,10-c net, while MS7b generates a 3D net with unusual ?-Sn topology. The photoluminescence properties Eu- and Tb-doped compounds (MS5-6) are also investigated, exhibiting strong red and green light emissions, respectively, which are attributed to the efficient energy transfer process from the BDC ligand to Eu³⁺ and Tb³⁺. Full article

(This article belongs to the Special Issue Coordination Polymers: New Materials for Multiple Applications)

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2764 KiB

Open AccessArticle

Systematic Limitations in Concentration Analysis via Anomalous Small-Angle X-ray Scattering in the Small Structure Limit

by Guenter Goerigk, Sebastian Lages and Klaus Huber

Polymers 2016, 8(3), 85; https://doi.org/10.3390/polym8030085 - 16 Mar 2016

Cited by 2 | Viewed by 11052

Abstract

Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb²⁺ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering [...] Read more.

Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb²⁺ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering contribution of the Pb²⁺ cations, and from subsequent analysis of the resonant-invariant, the amount of Pb²⁺ cations condensed onto the polyanions with respect to the total amount of Pb²⁺ cations in the solvent was estimated. In order to scrutinize systematic limitations in the determination of the chemical concentrations of resonant scattering counterions in the collapsed phase, Monte Carlo simulations have been performed. The simulations are based on structural confinements at variable size in the range of few nanometers, which represent the collapsed subdomains in the polyanions. These confinements were gradually filled to a high degree of the volume fraction with resonant scattering counterions giving access to a resonant-invariant at a variable degree of filling. The simulations revealed in the limit of small structures a significant underestimation of the true degree of filling of the collapsed subdomains when determining chemical concentrations of Pb²⁺ cations from the resonant invariant. Full article

(This article belongs to the Collection Polyelectrolytes)

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Full article ">Figure 1
(a) SAXS curves of samples FRM01 and FRM02 measured at three different X-ray energies in the vicinity of the LIII-absorption edge of Pb at 13,035 eV. The curves with the label “total” represent the total scattering, while the curves with label “pure” represent the form factor of the pure-resonant contribution. Note that the separated form factor of the pure-resonant scattering contribution is more than three orders of magnitude smaller with a cross-section down towards 10–5 cm−1 (!) when compared to the total scattering (factor 2000); (b) SANS curve of the sample FRM02. The solid lines running through the symbols of the scattering curves are fitted their respective scaled model functions representing the “freely jointed chain pearl necklace” FJC-PN model (see text). Full article ">Figure 2
The resonant invariant of the Pb counterions. From the integral the Pbconcentrations in the condensed phase is deduced. The blue lines represent the FJC-PN model (see text). Full article ">Figure 3
XANES spectrum of FRM02 measured at the Pb LIII-edge at 13,035 eV. The solid (black) line represents the XANES spectrum of a Pb-metal foil (y-axis on the left). The FRM02 spectrum reveals a chemical shift of about 5 eV. Δμd is the difference of the absorption coefficient times the sample thickness and represents the Pb-LIII-edge of the sample taken from the y-axis on the right. Full article ">Figure 4
Kratky plot of scattering curves calculated from scattering curves of Pb2+ ions confined in a cube of 1 nm side length by Monte Carlo simulation under the condition of a standard SAXS experiment (a). For the Pb2+ ions a spherical form factor with a radius of 0.119 nm was assumed. The structure factor of 5, 20, 40, 80, and 100 Pb ions with randomly-distributed distances inside a real gas was simulated. The curves are normalized to N. The same simulations have been repeated for the real gas under the condition of ASAXS measurements using point-like scattering centers. For q-values beyond 20 nm−1 the simulated curves are divided by 10 in order to better visualize (b). Full article ">Figure 5
Two integrals of normalized ASAXS and SAXS Kratky plots have been calculated for four different cubic confinements (1, 2, 4, and 6.5 nm) under the condition of a standard small-angle scattering experiment over the two integration intervals 0< q < 10 nm−1 (a) and 0< q < 2 nm−1 (b). The grey parallelogram represents the area of small confinements with low filling degrees compatible with results from the RI-analysis and XANES (see text). Full article ">

2999 KiB

Open AccessFeature PaperArticle

Enzymatic Synthesis and Characterization of Hydrophilic Sugar Based Polyesters and Their Modification with Stearic Acid

by Muhammad Humayun Bilal, Marko Prehm, Andrew Efraim Njau, Muhammad Haris Samiullah, Annette Meister and Jörg Kressler

Polymers 2016, 8(3), 80; https://doi.org/10.3390/polym8030080 - 16 Mar 2016

Cited by 22 | Viewed by 9817

Abstract

Biodegradable and hydrophilic functional polyesters were synthesized enzymatically using xylitol or d-sorbitol together with divinyl adipate and lipase B from Candida antartica (CAL-B). The resulting polyesters had pendant OH-groups from their sugar units which were esterified to different degrees with stearic acid [...] Read more.

Biodegradable and hydrophilic functional polyesters were synthesized enzymatically using xylitol or d-sorbitol together with divinyl adipate and lipase B from Candida antartica (CAL-B). The resulting polyesters had pendant OH-groups from their sugar units which were esterified to different degrees with stearic acid chloride. The structure and the degrees of polymerization of the resulting graft copolymers based on poly(xylitol adipate) and poly(d-sorbitol adipate) were characterized by ¹H NMR spectroscopy and SEC. DSC, WAXS and SAXS measurements indicated that a phase separation between polymer backbone and stearoyl side chains occurred in the graft copolymers, and, additionally, the side chains were able to crystallize which resulted in the formation of a lamellar morphology. Additionally, nanoparticles of the graft copolymers in an aqueous environment were studied by DLS and negative stain TEM. Full article

(This article belongs to the Special Issue Polymers for Aqueous Media)

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1H NMR spectra of (a) grafted and non-grafted poly(xylitol adipate) and (b) grafted and non-grafted poly(d-sorbitol adipate), recorded at 25 °C using CDCl3 and DMSO-d6 as solvent for grafted and non-grafted polymers, respectively. Full article ">Figure 2
Size exclusion chromatography (SEC) traces of (a) stearoyl grafed poly(xylitol adipate) in THF; (b) SEC traces of stearoyl grafted poly(d-sorbitol adipate) in THF. The insets show the SEC traces of the polymer backbones PXA and PDSA, respectively, in DMF. Full article ">Figure 3
DSC traces of (a) grafted and non-grafted PXA and (b) grafted and non-grafted PDSA. The measurements are carried out with a heating rate of 10 K·min−1. Full article ">Figure 4
Combined SAXS and WAXS traces during heating and cooling cycles (5 K step from 25 °C to 70 °C and back to 25 °C) of (a) PXA-g-S15; (b) PXA-g-S36; (c) PDSA-g-S68; and (d) PDSA-g-S10. Full article ">Figure 5
(a) Hydrodynamic radius distribution of PXA-g-S15 nanoparticles in water with a concentration of 1 g∙L−1 at 25 °C; (b) hydrodynamic radius distribution of PDSA-g-S10 nanoparticles (1g∙L−1 in water at 25 °C). Full article ">Figure 6
Negative-staining electron micrographs, (a) 0.1% dispersion of PXA-g-S15; (b) 0.1% dispersion of PDSA-g-S10. Full article ">Figure 7
Synthetic route to stearoyl grafted poly(xylitol adipate) (PXA-g-S) and poly(d-sorbitol adipate) (PDSA-g-S). Full article ">

1755 KiB

Open AccessFeature PaperArticle

Hybrid Polymer-Network Hydrogels with Tunable Mechanical Response

by Sebastian Czarnecki, Torsten Rossow and Sebastian Seiffert

Polymers 2016, 8(3), 82; https://doi.org/10.3390/polym8030082 - 15 Mar 2016

Cited by 35 | Viewed by 10250

Abstract

Hybrid polymer-network gels built by both physical and covalent polymer crosslinking combine the advantages of both these crosslinking types: they exhibit high mechanical strength along with excellent fracture toughness and extensibility. If these materials are extensively deformed, their physical crosslinks can break such [...] Read more.

Hybrid polymer-network gels built by both physical and covalent polymer crosslinking combine the advantages of both these crosslinking types: they exhibit high mechanical strength along with excellent fracture toughness and extensibility. If these materials are extensively deformed, their physical crosslinks can break such that strain energy is dissipated and irreversible fracturing is restricted to high strain only. This mechanism of energy dissipation is determined by the kinetics and thermodynamics of the physical crosslinking contribution. In this paper, we present a poly(ethylene glycol) (PEG) based material toolkit to control these contributions in a rational and custom fashion. We form well-defined covalent polymer-network gels with regularly distributed additional supramolecular mechanical fuse links, whose strength of connectivity can be tuned without affecting the primary polymer-network composition. This is possible because the supramolecular fuse links are based on terpyridine–metal complexation, such that the mere choice of the fuse-linking metal ion adjusts their kinetics and thermodynamics of complexation–decomplexation, which directly affects the mechanical properties of the hybrid gels. We use oscillatory shear rheology to demonstrate this rational control and enhancement of the mechanical properties of the hybrid gels. In addition, static light scattering reveals their highly regular and well-defined polymer-network structures. As a result of both, the present approach provides an easy and reliable concept for preparing hybrid polymer-network gels with rationally designed properties. Full article

(This article belongs to the Special Issue Polymers for Aqueous Media)

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Formation of hybrid polymer-network gels that contain both covalent and physical crosslinks. For this purpose, linear poly(ethylene glycol) (PEG) is functionalized with both azide (N3) and terpyridine (TPy) moieties at each end, and tetra-arm PEG is functionalized with cyclooctynes (CyOct) capped to each arm. After mixing aqueous solutions of both these PEG compounds, gelation occurs by strain-promoted azide–alkyne cycloaddition forming triazole linking units sketched as blue pentagons in the schematic. Addition of metal(II) ions, sketched as red circles in the schematic, leads to formation of intramolecular or intermolecular mechanical fuse links due to complexation to the additional terpyridine moieties on the polymer. Upon stretching, these hybrid gel-networks first respond in a linear rubbery-elastic fashion, before overstretching results in breakage of the transient metal–terpyridine bis-complexes, thereby dissipating strain energy, while leaving the covalent polymer crosslinking intact. Upon de-stretching, the metal–terpyridine bis-complexes are reformed. The illustrated hybrid polymer-network is drawn in an idealized fashion without loops or dangling chains; the data presented in this work indeed support this ideal picture and suggest the minor extent of such imperfection. Full article ">Figure 2
1H-NMR spectra of PEG-hydroxy-azide (top), PEG-hydroxy-terpyridine (center) and PEG-terpyridinyl-azide (bottom) in a chemical-shift range of 4–9 ppm, where the signals of the compounds differ most significantly. Full article ">Figure 3
Frequency-dependent shear moduli of the (A) purely covalent gel and the (B) Zn2+-, (C) Mn2+-; and (D) Co2+-terpyridine-enforced hybrid gels, each probed at a total polymer concentration of 100 g L−1 in water. All plots show the elastic (full symbols, G′) and viscous (open symbols, G′′) parts of the complex shear modulus, G, as a function of the test frequency, ω. Grey triangles denote data obtained at 10 °C, while black diamonds denote data obtained at 25 °C. All data are superimposed by shifting the 10 °C data along the frequency axes to obtain master curves according to the principle of time-temperature-superposition, referenced to 25 °C. The vertical dashed red line in (B) denotes ω = kdiss. of the Zn2+–terpyridine complexes. Full article ">Figure 4
Amplitude-dependent shear moduli of the (A) purely covalent gel and the (B) Zn2+-, (C) Mn2+-; and (D) Co2+-terpyridine-enforced hybrid gels, each probed at a total polymer concentration of 100 g L−1 in water. All plots show the elastic (full symbols, G′) and viscous (open symbols, G′′) parts of the complex shear modulus, G, as a function of the shear-deformation amplitude, γ, at 25 °C. Full article ">Figure 5
Static light scattering data used to evaluate the spatial polymer network inhomogeneity of the (A,E) purely covalent gel and of the (B,F) Zn2+-, (C,G) Mn2+-, and (D,H) Co2+-terpyridine-enforced hybrid gels, each probed at a total polymer concentration of 100 g·L−1 in water. (A–D) Rayleigh ratios, Rθ, of the gels (full symbols) and of an uncrosslinked reference sample (open symbols); (E–H) Debye-Bueche plots of the excess scattering intensities, RE(q), calculated as the difference between the angle-resolved Rayleigh ratios of the crosslinked and uncrosslinked samples. Full article ">Figure 6
Synthesis of (A) linear PEG-azide (1), (B) propargyl-terpyridine (2); (C) linear PEG-terpyridinyl-azide (5); and (D) tetra-arm PEG-bicyclo[6.1.0]non-4-yn-9-ylmethyl carbamate (8). Full article ">

2747 KiB

Open AccessArticle

Polymer Inclusion Membranes (PIM) for the Recovery of Potassium in the Presence of Competitive Cations

by Anna Casadellà, Olivier Schaetzle, Kitty Nijmeijer and Katja Loos

Polymers 2016, 8(3), 76; https://doi.org/10.3390/polym8030076 - 15 Mar 2016

Cited by 31 | Viewed by 13565

Abstract

Potassium is an important nutrient used in fertilizers but is not always naturally available We investigated the properties of polymer inclusion membranes (PIM) regarding their selective recovery of K⁺ over competitive ions typically present in urine (Na⁺ and NH₄⁺ [...] Read more.

Potassium is an important nutrient used in fertilizers but is not always naturally available We investigated the properties of polymer inclusion membranes (PIM) regarding their selective recovery of K⁺ over competitive ions typically present in urine (Na⁺ and NH₄⁺). The greatest flux was observed when the ratio of mass 2-nitrophenyl octyl ether (2-NPOE) used as plasticizer to cellulose triacetate (CTA) used as polymer was 0.25. The highest flux was achieved with a content of 24.8 wt % of dicyclohexan-18-crown-6 (DCH18C6) used as carrier, although the highest selectivity was observed with a content of 14.0 wt % of DCH18C6. We also studied whether the transport mechanism occurring in our system was based on co-transport of a counter-ion or ion exchange. Two different receiving phases (ultrapure water and 100 mM HCl) were tested. Results on transport mechanisms suggest that co-transport of cations and anions is taking place across our PIMs. The membrane deteriorated and lost its properties when the receiving phase was acidic; we suggested that this was due to hydrolysis of CTA. The greatest flux and selectivity were observed in ultrapure water as receiving phase. Full article

(This article belongs to the Special Issue Polymer Thin Films and Membranes 2015)

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3238 KiB

Open AccessArticle

Surface Property Modification of Silver Nanoparticles with Dopamine-Functionalized Poly(pentafluorostyrene) via RAFT Polymerization

by Ka Wai Fan and Anthony Michael Granville

Polymers 2016, 8(3), 81; https://doi.org/10.3390/polym8030081 - 14 Mar 2016

Cited by 15 | Viewed by 8887

Abstract

This research aims to synthesize a dopamine-functionalized macromolecular anchor to perform surface modification on the target nanostructures. A molecular anchor, 3,4-dichloro-1-[2-(3,4-dihydroxyphenyl)ethyl]-1H-pyrrole-2,5-dione, was successfully synthesized from dopamine and 2,3-dichloromaleic anhydride. The anchor acted as a linkage to couple the chains of poly(pentafluorostyrene) [...] Read more.

This research aims to synthesize a dopamine-functionalized macromolecular anchor to perform surface modification on the target nanostructures. A molecular anchor, 3,4-dichloro-1-[2-(3,4-dihydroxyphenyl)ethyl]-1H-pyrrole-2,5-dione, was successfully synthesized from dopamine and 2,3-dichloromaleic anhydride. The anchor acted as a linkage to couple the chains of poly(pentafluorostyrene) (PPFS) which were synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Modification was successfully performed to silver nanoparticles (AgNPs) by deposition of the dopamine-functionalized coupled PPFS onto the surface of the particles. The modified AgNPs had demonstrated improved dispersibility in organic solvent due to the hydrophobic nature of PPFS. To modify the surface chemistry of the nanoparticles further, thioglucose was grafted onto the structure of the coupled PPFS via thiol-fluoro nucleophilic substitution at the para-position of the pentafluorophenyl groups on the monomer units. The presence of sugar moieties on the coupled PPFS increased its hydrophilicity, which allowed the modified AgNPs to be readily dispersed in aqueous solvent. Full article

(This article belongs to the Special Issue Controlled/Living Radical Polymerization)

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Gel Permeation Chromatography (GPC) analysis of PPFS chains (black) and coupled PPFS (blue) with DA-DCMA anchor. Full article ">Figure 2
Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis of coupled PPFS and anchored PPFS@AgNPs. Full article ">Figure 3
SEM image of AgNPs (left) and PPFS coupled AgNPs (PPFS@AgNPs) (right). Full article ">Figure 4
TGA analysis of bare AgNP, RAFT generated DA-DCMA coupled PPFS chains, and PPFS coupled to AgNPs (PPFS@AgNPs). Full article ">Figure 5
Dispersion of modified GPPFS@AgNPs in water before (left) and after (right) sonication. Full article ">Figure 6
TGA analysis of bare AgNP, DA-DCMA coupled glycosylated PPFS (GPPFS) chains, and GPPFS coupled to AgNPs (GPPFS@AgNPs). Full article ">Figure 7
Reaction steps for generating poly(pentafluorostyrene) (PPFS) y-brush with dopamine based anchor. Full article ">

488 KiB

Open AccessArticle

The Backfolded Odijk Regime for Wormlike Chains Confined in Rectangular Nanochannels

by Abhiram Muralidhar, Michael J. Quevillon and Kevin D. Dorfman

Polymers 2016, 8(3), 79; https://doi.org/10.3390/polym8030079 - 14 Mar 2016

Cited by 23 | Viewed by 7009

Abstract

We confirm Odijk’s scaling laws for (i) the average chain extension; (ii) the variance about the average extension; and (iii) the confinement free energy of a wormlike chain confined in a rectangular nanochannel smaller than its chain persistence length through pruned-enriched Rosenbluth method [...] Read more.

We confirm Odijk’s scaling laws for (i) the average chain extension; (ii) the variance about the average extension; and (iii) the confinement free energy of a wormlike chain confined in a rectangular nanochannel smaller than its chain persistence length through pruned-enriched Rosenbluth method (PERM) simulations of asymptotically long, discrete wormlike chains. In the course of this analysis, we also computed the global persistence length of ideal wormlike chains for the modestly rectangular channels that are used in many experimental systems. The results are relevant to genomic mapping systems that confine DNA in channel sizes around 50 nm, since fabrication constraints generally lead to rectangular cross-sections. Full article

(This article belongs to the Special Issue Semiflexible Polymers)

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2627 KiB

Open AccessArticle

Highly Active Copolymerization of Ethylene and N-Acetyl-O-(?-Alkenyl)-l-Tyrosine Ethyl Esters Catalyzed by Titanium Complex

by Jing Wang, Hongming Li, Runcong Zhang, Xianghui Shi, Jianjun Yi, Jian Wang, Qigu Huang and Wantai Yang

Polymers 2016, 8(3), 64; https://doi.org/10.3390/polym8030064 - 10 Mar 2016

Cited by 5 | Viewed by 8116

Abstract

A series of N-acetyl-O-(?-alkenyl)-l-tyrosine ethyl esters were synthesized by the reaction of vinyl bromides (4-bromo-1-butene, 6-bromo-1-hexene, 8-bromo-1-octene and 10-bromo-1-decene) with N-acetyl-l-tyrosine ethyl ester. ¹H NMR, elemental analysis, FT-IR, and mass spectra were performed for [...] Read more.

A series of N-acetyl-O-(?-alkenyl)-l-tyrosine ethyl esters were synthesized by the reaction of vinyl bromides (4-bromo-1-butene, 6-bromo-1-hexene, 8-bromo-1-octene and 10-bromo-1-decene) with N-acetyl-l-tyrosine ethyl ester. ¹H NMR, elemental analysis, FT-IR, and mass spectra were performed for these N-acetyl-O-(?-alkenyl)-l-tyrosine ethyl esters. The novel titanium complex can catalyze the copolymerization of ethylene and N-acetyl-O-(?-alkenyl)-l-tyrosine ethyl esters efficiently and the highest catalytic activity was up to 6.86 × 10⁴ gP·(molTi)^?1·h^?1. The structures and properties of the obtained copolymers were characterized by FT-IR, (¹H)¹³C NMR, GPC, DSC, and water contact angle. The results indicated that the obtained copolymers had a uniformly high average molecular weight of 2.85 × 10⁵ g·mol^?1 and a high incorporation ratio of N-acetyl-O-(but-3-enyl)-l-tyrosine ethyl ester of 2.65 mol % within the copolymer chain. The units of the comonomer were isolated within the copolymer chains. The insertion of the polar comonomer into a copolymer chain can effectively improve the hydrophilicity of a copolymer. Full article

(This article belongs to the Special Issue Metal-Mediated Polymer Synthesis)

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1536 KiB

Open AccessCommunication

Polylactide/Montmorillonite Hybrid Latex as a Barrier Coating for Paper Applications

by Davide Bandera, Veronika R. Meyer, David Prevost, Tanja Zimmermann and Luciano F. Boesel

Polymers 2016, 8(3), 75; https://doi.org/10.3390/polym8030075 - 4 Mar 2016

Cited by 19 | Viewed by 7440

Abstract

We developed a paper coating for the potential application in food packaging based on polylactide and montmorillonite. It is applied to the paper in the form of a stable, water-based latex with a solid content of 25–28 wt %. The latex is prepared [...] Read more.

We developed a paper coating for the potential application in food packaging based on polylactide and montmorillonite. It is applied to the paper in the form of a stable, water-based latex with a solid content of 25–28 wt %. The latex is prepared from a commercially available polylactide, surfactants, montmorillonite, a plasticizer, chloroform (to be removed later) and water by an emulsion/solvent evaporation procedure. This coating formulation is applied to the paper substrate by bar-coating, followed by hot-pressing at 150 °C. The coated papers achieved up to an 85% improvement in water vapor transmission rates when compared to the pristine papers. The coating latex is prepared from inexpensive materials and can be used for a solvent-free coating process. In addition, the ingredients of the latex are non-toxic; thus, the coated papers can be safely used for food packaging. Full article

(This article belongs to the Special Issue Biodegradable Polymers)

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4387 KiB

Open AccessArticle

Fabrication of Alkoxyamine-Functionalized Magnetic Core-Shell Microspheres via Reflux Precipitation Polymerization for Glycopeptide Enrichment

by Meng Yu, Yi Di, Ying Zhang, Yuting Zhang, Jia Guo, Haojie Lu and Changchun Wang

Polymers 2016, 8(3), 74; https://doi.org/10.3390/polym8030074 - 4 Mar 2016

Cited by 11 | Viewed by 9105

Abstract

As a facile method to prepare hydrophilic polymeric microspheres, reflux precipitation polymerization has been widely used for preparation of polymer nanogels. In this article, we synthesized a phthalamide-protected N-aminooxy methyl acrylamide (NAMAm-p) for preparation of alkoxyamine-functionalized polymer composite microspheres via [...] Read more.

As a facile method to prepare hydrophilic polymeric microspheres, reflux precipitation polymerization has been widely used for preparation of polymer nanogels. In this article, we synthesized a phthalamide-protected N-aminooxy methyl acrylamide (NAMAm-p) for preparation of alkoxyamine-functionalized polymer composite microspheres via reflux precipitation polymerization. The particle size and functional group density of the composite microspheres could be adjusted by copolymerization with the second monomers, N-isopropyl acrylamide, acrylic acid or 2-hydroxyethyl methacrylate. The resultant microspheres have been characterized by TEM, FT-IR, TGA and DLS. The experimental results showed that the alkoxyamine group density of the microspheres could reach as high as 1.49 mmol/g, and these groups showed a great reactivity with ketone/aldehyde compounds. With the aid of magnetic core, the hybrid microspheres could capture and magnetically isolate glycopeptides from the digested mixture of glycopeptides and non-glycopeptides at a 1:100 molar ratio. After that, we applied the composite microspheres to profile the glycol-proteome of a normal human serum sample, 95 unique glycopeptides and 64 glycoproteins were identified with these enrichment substrates in a 5 ?L of serum sample. Full article

(This article belongs to the Special Issue Selected Papers from ASEPFPM2015)

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5040 KiB

Open AccessArticle

Processing-Induced Inhomogeneity of Yield Stress in Polycarbonate Product and Its Influence on the Impact Behavior

by Yingjie Xu, Huan Lu, Tenglong Gao and Weihong Zhang

Polymers 2016, 8(3), 72; https://doi.org/10.3390/polym8030072 - 4 Mar 2016

Cited by 9 | Viewed by 6104

Abstract

In this study, an integrated methodology for impact analysis of polycarbonate (PC) product is proposed which incorporates the processing-induced inhomogeneity of yield stress. A previously developed model is extended to predict the inhomogeneous yield stress distribution along the specimen by using the thermal [...] Read more.

In this study, an integrated methodology for impact analysis of polycarbonate (PC) product is proposed which incorporates the processing-induced inhomogeneity of yield stress. A previously developed model is extended to predict the inhomogeneous yield stress distribution along the specimen by using the thermal history experienced during injection molding. A strain rate-dependent elastic-plastic model combining the processing-induced yield stress is applied to model the mechanical behavior of PC. Finite element simulation for notched Izod impact test is then conducted to analyze the impact behaviors of PC specimens with different thermal histories. Numerical results of the fracture energies are compared with experimental measurements. Full article

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6678 KiB

Open AccessArticle

Polyelectrolyte Threading through a Nanopore

by Pai-Yi Hsiao

Polymers 2016, 8(3), 73; https://doi.org/10.3390/polym8030073 - 3 Mar 2016

Cited by 12 | Viewed by 6821

Abstract

Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time ? ? ? is shown to follow a scaling law N^?, and the exponent ? increases monotonically from [...] Read more.

Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time ? ? ? is shown to follow a scaling law N^?, and the exponent ? increases monotonically from 1.16 (4) to 1.40 (3) with E. The result is double-checked by the calculation of mean square displacement of translocation coordinate, which asserts a scaling behavior t^? (for t near ?) with ? complying with the relation ?? = 2. At a fixed chain length N, ??? displayed a reciprocal scaling behavior E^?1 in the weak and also in the strong fields, connected by a transition E^?1.64(5) in the intermediate fields. The variations of the radius of gyration of chain and the positions of chain end are monitored during a translocation process; far-from-equilibrium behaviors are observed when the driving field is strong. A strong field can strip off the condensed ions on the chain when it passes the pore. The total charges of condensed ions are hence decreased. The studies for the probability and density distributions reveal that the monomers in the trans-region are gathered near the wall and form a pancake-like density profile with a hump cloud over it in the strong fields, due to fast translocation. Full article

(This article belongs to the Collection Polyelectrolytes)

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5619 KiB

Open AccessArticle

Near Surface Mounted Composites for Flexural Strengthening of Reinforced Concrete Beams

by Md. Akter Hosen, Mohd Zamin Jumaat, Ubagaram Johnson Alengaram, A. B. M. Saiful Islam and Huzaifa Bin Hashim

Polymers 2016, 8(3), 67; https://doi.org/10.3390/polym8030067 - 3 Mar 2016

Cited by 35 | Viewed by 10931

Abstract

Existing structural components require strengthening after a certain period of time due to increases in service loads, errors in design, mechanical damage, and the need to extend the service period. Externally-bonded reinforcement (EBR) and near-surface mounted (NSM) reinforcement are two preferred strengthening approach. [...] Read more.

Existing structural components require strengthening after a certain period of time due to increases in service loads, errors in design, mechanical damage, and the need to extend the service period. Externally-bonded reinforcement (EBR) and near-surface mounted (NSM) reinforcement are two preferred strengthening approach. This paper presents a NSM technique incorporating NSM composites, namely steel and carbon fiber-reinforced polymer (CFRP) bars, as reinforcement. Experimental and analytical studies carried out to explore the performance of reinforced concrete (RC) members strengthened with the NSM composites. Analytical models were developed in predicting the maximum crack spacing and width, concrete cover separation failure loads, and deflection. A four-point bending test was applied on beams strengthened with different types and ratios of NSM reinforcement. The failure characteristics, yield, and ultimate capacities, deflection, strain, and cracking behavior of the beams were evaluated based on the experimental output. The test results indicate an increase in the cracking load of 69% and an increase in the ultimate load of 92% compared with the control beam. The predicted result from the analytical model shows good agreement with the experimental result, which ensures the competent implementation of the present NSM-steel and CFRP technique. Full article

(This article belongs to the Collection Fiber-Reinforced Polymer Composites in Structural Engineering)

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4213 KiB

Open AccessReview

Biopolymeric Mucin and Synthetic Polymer Analogs: Their Structure, Function and Role in Biomedical Applications

by Sundar P. Authimoolam and Thomas D. Dziubla

Polymers 2016, 8(3), 71; https://doi.org/10.3390/polym8030071 - 2 Mar 2016

Cited by 64 | Viewed by 21809

Abstract

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of [...] Read more.

Mucin networks are viscoelastic fibrillar aggregates formed through the complex self-association of biopolymeric glycoprotein chains. The networks form a lubricious, hydrated protective shield along epithelial regions within the human body. The critical role played by mucin networks in impacting the transport properties of biofunctional molecules (e.g., biogenic molecules, probes, nanoparticles), and its effect on bioavailability are well described in the literature. An alternate perspective is provided in this paper, presenting mucin’s complex network structure, and its interdependent functional characteristics in human physiology. We highlight the recent advances that were achieved through the use of mucin in diverse areas of bioengineering applications (e.g., drug delivery, biomedical devices and tissue engineering). Mucin network formation is a highly complex process, driven by wide variety of molecular interactions, and the network possess structural and chemical variations, posing a great challenge to understand mucin’s bulk behavior. Through this review, the prospective potential of polymer based analogs to serve as mucin mimic is suggested. These analog systems, apart from functioning as an artificial model, reducing the current dependency on animal models, can aid in furthering our fundamental understanding of such complex structures. Full article

(This article belongs to the Special Issue Polymers Applied in Tissue Engineering)

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142 KiB

Open AccessEditorial

Organic Photovoltaics: More than Ever, an Interdisciplinary Field

by Laure Biniek and Christian B. Nielsen

Polymers 2016, 8(3), 70; https://doi.org/10.3390/polym8030070 - 2 Mar 2016

Cited by 3 | Viewed by 4680

Abstract

Despite the growing interest and rapid advancement of alternative photovoltaic (PV) technologies such as perovskite based PV devices, we still believe that organic photovoltaic (OPV) devices have a significant potential for stable, low-cost solar power generation. [...] Full article

(This article belongs to the Special Issue Organic Photovoltaics)

759 KiB

Open AccessArticle

ICAR ATRP of Acrylonitrile under Ambient and High Pressure

by Zhicheng Huang, Jing Chen, Lifen Zhang, Zhenping Cheng and Xiulin Zhu

Polymers 2016, 8(3), 59; https://doi.org/10.3390/polym8030059 - 2 Mar 2016

Cited by 25 | Viewed by 7990

Abstract

It is well known that well-defined polyacrylonitrile (PAN) with high molecular weight (M_w > 106 g·mol^?1) is an excellent precursor for high performance carbon fiber. In this work, a strategy for initiators for a continuous activator regeneration atom transfer [...] Read more.

It is well known that well-defined polyacrylonitrile (PAN) with high molecular weight (M_w > 106 g·mol^?1) is an excellent precursor for high performance carbon fiber. In this work, a strategy for initiators for a continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) system for acrylonitrile (AN) was firstly established by using CuCl₂·2H₂O as the catalyst and 2,2?-azobis(2-methylpropionitrile) (AIBN) as the thermal initiator in the presence of ppm level catalyst under ambient and high pressure (5 kbar). The effect of catalyst concentration and polymerization temperature on the polymerization behaviors was investigated. It is important that PAN with ultrahigh viscosity and average molecular weight (M_? = 1,034,500 g·mol^?1) could be synthesized within 2 h under high pressure. Full article

(This article belongs to the Special Issue Controlled/Living Radical Polymerization)

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1660 KiB

Open AccessArticle

Homo- and Copolymerization of Ethylene and Norbornene with Anilido–Imine Chromium Catalysts

by Lixia Pei, Yong Tang and Haiyang Gao

Polymers 2016, 8(3), 69; https://doi.org/10.3390/polym8030069 - 1 Mar 2016

Cited by 16 | Viewed by 7466

Abstract

A series of anilido–imine chromium complexes have been used as precursors to catalyze homo- and copolymerization of ethylene and norbornene. The chromium complexes activated with methylalumoxane (MAO) exhibit good activities for homopolymerization of ethylene (E) to produce linear polyethylene and moderate activities for [...] Read more.

A series of anilido–imine chromium complexes have been used as precursors to catalyze homo- and copolymerization of ethylene and norbornene. The chromium complexes activated with methylalumoxane (MAO) exhibit good activities for homopolymerization of ethylene (E) to produce linear polyethylene and moderate activities for norbornene (N) polymerization to afford vinyl-type polynorbornene. Ethylene–norbornene copolymers with high incorporation of norbornene can be also produced by these catalysts. ¹³C NMR and differential scanning calorimetry (DSC) analyses show that the copolymers are random products, and –NNN– and –EEE– units can be observed in the microstructure of the copolymers. Full article

(This article belongs to the Special Issue Metal-Mediated Polymer Synthesis)

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Polymers, Volume 8, Issue 3 (March 2016) – 41 articles

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