Disclosure of Invention
The invention aims to provide a preparation method of a force-induced discoloration self-repairing elastic film, which has the advantages of stable structure, high copolymerization reaction rate, high monomer conversion rate and mild reaction conditions, the force-induced discoloration self-repairing elastic film prepared by the method and application of the force-induced discoloration self-repairing elastic film.
In order to achieve the aim, the invention provides a preparation method of a force-induced color-changing self-repairing elastic film, which comprises the following steps:
s1, preparing a stimulus-responsive compound spiropyran derivative or rhodamine derivative with two ends as hydroxyl groups for later use;
s2, preparing a cross-linking agent, wherein the end group of the cross-linking agent is a double bond, the middle part of the cross-linking agent is an amido bond and contains a spiropyran derivative or a rhodamine derivative, and the structural formula of the cross-linking agent is as follows:
s3, preparing the force-induced color-changing self-repairing elastic film: and (4) carrying out free radical polymerization reaction on two monomers and the cross-linking agent prepared in the step S2 under the action of a free radical polymerization initiator to obtain the force-induced color-changing self-repairing elastic film.
As a further improvement of the present invention, the step S2 includes the following steps:
adding an organotin catalyst into an isocyano ester compound, then adding an organic solution containing the spiropyran derivative or rhodamine derivative prepared in the step S1, and reacting for 3-5 hours at the temperature of 20-40 ℃ to prepare the cross-linking agent.
As a further improvement of the invention, the structural formula of the spiropyran derivative is as follows:
as a further improvement of the invention, the structural formula of the rhodamine derivative is as follows:
as a further improvement of the present invention, in step S2, the isocyano ester compound is one of isocyano ethyl methacrylate, isocyano ethyl acrylate or 3-isopropenyl- α, α -dimethylbenzyl isocyanate; the organic tin catalyst comprises but is not limited to one of dibutyltin dilaurate, tetraphenyltin, stannous octoate and dimethyl tin.
As a further improvement of the present invention, the step S3 includes the following steps:
mixing a hard chain segment monomer and a soft chain segment monomer with the cross-linking agent prepared in the step S2, adding a free radical polymerization initiator, and carrying out free radical polymerization reaction for 6-12 hours at a preset temperature to obtain the force-induced color-changing self-repairing elastic film; the mole ratio of the hard chain segment monomer to the soft chain segment monomer is 2: 1-1: 5, the preset temperature is 60-80 ℃, the initiator accounts for 0.5-3% of the two monomers in mole percentage, and the cross-linking agent accounts for 0.01-0.3% of the two monomers in mole percentage.
As a further improvement of the invention, the hard segment monomer includes but is not limited to one of methyl methacrylate, acrylonitrile, acrylamide, styrene, methyl acrylate or vinyl acetate.
As a further improvement of the present invention, the soft segment monomer includes, but is not limited to, one of ethyl acrylate, butyl acrylate, or isooctyl acrylate.
In order to achieve the purpose, the invention further provides the force-induced color-changing self-repairing elastic film prepared by the preparation method of the force-induced color-changing self-repairing elastic film according to any one of the technical schemes.
In order to achieve the purpose, the invention also provides an application of the force-induced color-changing self-repairing elastic film or the force-induced color-changing self-repairing elastic film prepared by the preparation method according to any one of the technical schemes in the field of force-induced color-changing self-repairing materials.
The invention has the beneficial effects that:
1. according to the preparation method, under the action of a free radical polymerization initiator, a self-designed and synthesized cross-linking agent and a corresponding monomer are subjected to free radical polymerization reaction to obtain the force-induced color-changing self-repairing elastic film. The free radical polymerization has the advantages of high reaction rate, high monomer conversion rate, mild reaction conditions, and quick, simple and controllable operation process.
2. The preparation method of the invention uses a cross-linking agent containing small molecule spiropyran derivative or rhodamine derivative; the cross-linking agent has a simple structure, has an amido bond in the middle, can have a self-repairing function when a material is damaged based on a hydrogen bond effect, and has higher activity and higher reaction efficiency because the two ends are carbon-carbon double bonds compared with other structures.
3. The cross-linking agent with double bonds at two ends is used in the preparation process of the force-induced discoloration self-repairing elastic film, when the cross-linking agent participates in copolymerization reaction, the generated copolymer is in a cross-linked network structure, and when a good solvent of homopolymers of the two monomers is adopted to dissolve the force-induced discoloration self-repairing elastic film, the result shows that the force-induced discoloration self-repairing elastic film is not dissolved and can stably exist in the solvent, and the fact that the interior of the force-induced discoloration self-repairing elastic film is in the cross-linked network structure, stable in structure and resistant to chemical solvents is confirmed.
4. The force-induced color-changing self-repairing elastic film prepared by the invention can be used as a base material of flexible electronic and wearable equipment, and has wide application prospects in the fields of inkless writing, anti-counterfeiting, encryption and the like.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention.
Referring to fig. 1 to 5, the present invention provides a method for preparing a force-induced color-changing self-repairing elastic film, comprising the following steps:
s1, preparing a stimulus-responsive compound spiropyran derivative or rhodamine derivative with two ends as hydroxyl groups for later use;
s2, preparing a cross-linking agent, wherein the end group of the cross-linking agent is a double bond, the middle part of the cross-linking agent is an amido bond and contains a spiropyran derivative or a rhodamine derivative, and the structural formula of the cross-linking agent is as follows:
s3, preparing the force-induced color-changing self-repairing elastic film: and (4) carrying out free radical polymerization reaction on two monomers and the cross-linking agent prepared in the step S2 under the action of a free radical polymerization initiator to obtain the force-induced color-changing self-repairing elastic film.
Preferably, the spiropyran derivative has a structure of HO-SP1-OH, HO-SP2-OH or HO-SP3-OH, and the rhodamine derivative has a structure of HO-Rh-OH, and the structural formula is as follows:
the step S2 includes the following steps:
adding an organotin catalyst into an isocyano ester compound, then adding an organic solution containing the spiropyran derivative or rhodamine derivative prepared in the step S1, and reacting for 3-5 hours at the temperature of 20-40 ℃ to prepare the cross-linking agent.
The isocyano ester compound is one of isocyano ethyl methacrylate, isocyano ethyl acrylate or 3-isopropenyl-alpha, alpha-dimethyl benzyl isocyanate, and preferably isocyano ethyl methacrylate.
The organic tin catalyst is one of dibutyltin dilaurate, tetraphenyltin, stannous octoate and dimethyltin, and preferably dibutyltin dilaurate.
The procedure for the preparation of the crosslinker is illustrated by the reaction of the spiropyran derivative HO-SP2-OH with isocyanatoethyl methacrylate in dibutyltin dilaurate (DBTDL):
the process for preparing the cross-linking agent by adopting other spiropyran derivatives or rhodamine derivatives and other isocyano ester compounds is similar to the process, and is not described again.
The cross-linking agent containing the small molecule spiropyran derivative or rhodamine derivative is prepared through the process. The cross-linking agent has a simple structure, has an amido bond in the middle, and amide bond structures can form hydrogen bonds pairwise, can have a self-repairing function when a material is damaged based on the action of the hydrogen bonds; compared with other structures, the cross-linking agent has the advantages that the two ends are carbon-carbon double bonds, the activity is higher, and the reaction efficiency is higher.
The step S3 includes the following steps:
mixing a hard chain segment monomer and a soft chain segment monomer with the cross-linking agent prepared in the step S2, adding a free radical polymerization initiator, and carrying out free radical polymerization reaction for 6-12 hours at a preset temperature to obtain the force-induced color-changing self-repairing elastic film; the mole ratio of the hard chain segment monomer to the soft chain segment monomer is 2: 1-1: 5, the preset temperature is 60-80 ℃, the initiator accounts for 0.5-3% of the two monomers in mole percentage, and the cross-linking agent accounts for 0.01-0.3% of the two monomers in mole percentage.
The hard segment monomer may be any one of methyl methacrylate (105 deg.C), acrylonitrile (97 deg.C), acrylamide (165 deg.C), styrene (100 deg.C), methyl acrylate (8 deg.C), and vinyl acetate (22 deg.C).
The soft segment monomer may be any of ethyl acrylate (-22 deg.C), butyl acrylate (-55 deg.C), isooctyl acrylate (-70 deg.C).
The temperatures in parentheses above are the glass transition temperatures of the homopolymers of the corresponding monomers.
The initiator is any one of Azobisisobutyronitrile (AIBN), azobisisoheptonitrile, dibenzoyl peroxide or lauroyl peroxide.
The process for making the force-chromic self-healing elastic film of the present invention is described below in connection with examples 1-160:
example 1
S1, preparing a stimulus responsive compound, namely a spiropyran derivative HO-SP2-OH with two ends being hydroxyl groups for later use;
s2, preparation of cross-linker: adding dibutyltin dilaurate (DBTDL) into isocyano ethyl methacrylate, then adding an organic solution containing the dihydroxyspiropyran derivative prepared in the step S1, and reacting for 3-5 h at 20-40 ℃ to prepare a cross-linking agent which has double bonds as end groups and amide bonds in the middle and contains the spiropyran derivative;
the preparation process of the cross-linking agent is as follows:
s3, preparing the force-induced color-changing self-repairing elastic film:
mixing a hard chain segment monomer and a soft chain segment monomer with the cross-linking agent prepared in the step S2, adding a free radical polymerization initiator, and carrying out free radical polymerization reaction for 10 hours at a preset temperature to obtain the force-induced color-changing self-repairing elastic film; wherein the molar ratio of the hard segment monomer to the soft segment monomer is 1:1, the preset temperature is 70 ℃, the initiator accounts for 1 mol% of the two monomers, and the crosslinking agent accounts for 0.1 mol% of the two monomers.
The hard segment monomer may be any of methyl methacrylate (105 ℃ C.), acrylonitrile (97 ℃ C.), acrylamide (165 ℃ C.), styrene (100 ℃ C.), methyl acrylate (8 ℃ C.), and vinyl acetate (22 ℃ C.).
The soft segment monomer may be any of ethyl acrylate (-22 deg.C), butyl acrylate (-55 deg.C), isooctyl acrylate (-70 deg.C).
The invention also provides the force-induced color-changing self-repairing elastic film prepared by the preparation method.
Referring to FIGS. 1 to 5, the infrared absorption spectrum of the cross-linking agent prepared according to the embodiment shown in FIG. 1 is at 1452cm-1The position has a characteristic peak of N-C in amido bond at 1642cm-1The position has a characteristic peak of C ═ O in an amide bond, and the peak is 3688cm-1The position has a characteristic peak of-NH in amido bond, which indicates that the cross-linking agent containing amido bond is successfully synthesized by the method.
Referring to FIG. 2, the NMR spectrum data of the crosslinker prepared in this example are as follows:1H NMR(400MHz,CDCl3):δ8.11(s,1H,He),7.96(s,1H,Hd),7.16-7.12(t,2H,Hi),7.05-7.02(d,1H,Hf),7.02-6.75(dt,1H,Hj),6.61(d,1H,Hk),6.09(s,1H,Hp),5.56(s,1H,He),5.19(s,2H,Ha),4.49-4.41(m,2H,Hc),3.48-3.37(m,6H,Hb),2.95-2.87(dt,4H,Hm),1.92(s,6H,Hn),1.68-1.46(m,2H,Hl),1.26(s,6H,Hh)。
referring to FIG. 3, the NMR spectrum data of the crosslinker prepared in this example are as follows:13C NMR(101MHz,CDCl3):δ167.47(Cy),162.69(Ck),158.04(Cl),146.16(Cf),140.77(Cq),136.10(Ca),135.47(Cs),128.45(Cz),128.36(Cr),127.91(Cn),126.05(Cd),125.60(C2),124.15(Cp),122.52(Cb),122.09(Cm),121.98(Co),120.02(Cc),118.58(Ce),106.83(Cj),77.64-75.88(CCDCl3),64.21(Cv),63.59(Ct),60.68(Cx),52.98(Ci),40.26(Cu),36.56(Cw),31.54(C3),25.94(Cg),18.33(Ch)。
referring to fig. 4, the original state of the self-healing elastic membrane with force-induced discoloration of the present invention is light yellow (as shown in fig. 4 (a)), and when the elastic membrane is pressed by a mold, the color of the pressed part (WTU) changes to dark reddish brown (as shown in fig. 4 (b)), showing the force-induced discoloration; then, white light irradiation was performed on (b) in fig. 4, and it was seen that the discoloration by pressing was reduced to pale yellow (as in (c) in fig. 4).
Referring to fig. 5, after the surface of the self-repairing elastic film with force-induced discoloration is manufactured with scratches having a width of 25 μm or less (as shown in (a) of fig. 5) and placed in an environment at 50 ℃, the width of the scratches is found to be significantly reduced after 20 hours, and the scratches can be completely healed at a narrow position (as shown in (b) of fig. 5), thereby showing excellent self-repairing performance.
According to the analysis, the force-induced color-changing self-repairing elastic film has good force-induced color-changing and self-repairing performances, can be applied to the field of force-induced color-changing self-repairing materials, can be used as a base material of flexible electronics and wearable equipment, and can also be applied to the fields of inkless writing, anti-counterfeiting, encryption and the like.
Examples 2 to 8
Examples 2 to 8 and comparative examples 1 to 2 are different from example 1 in that the molar ratio of the hard segment monomer to the soft segment monomer is changed in step S3, and other steps are substantially the same as those of example 1 and are not described herein again; the molar ratios of the hard segment monomers to the soft segment monomers in examples 2-8 are shown in the following table:
item
|
Molar ratio of hard segment monomer to soft segment monomer
|
Example 1
|
1:1
|
Example 2
|
1:5
|
Example 3
|
1:2
|
Example 4
|
4:5
|
Example 5
|
6:5
|
Example 6
|
3:2
|
Example 7
|
9:5
|
Example 8
|
2:1
|
Comparative example 1
|
1:10
|
Comparative example 2
|
5:2 |
According to experiments, the mechanical property of the force-induced discoloration self-repairing elastic film is increased, the elastic property is reduced, and the force-induced discoloration sensitivity is improved with the increase of the molar ratio of the hard segment monomer to the soft segment monomer.
When the molar ratio of the hard segment monomer to the soft segment monomer is 1:10, the soft segment monomer has a high content, and thus the obtained polymer film has low mechanical properties, can bear low stress, and has no photochromic function.
When the molar ratio of the hard segment monomer to the soft segment monomer is 5:2, the hard segment monomer has high content, so that the polymer film has high mechanical property and a mechanochromic function, but the polymer film has high hardness and poor elastic property, and the application of the polymer film in flexible electronic and wearable equipment materials is limited.
Examples 9 to 13
Examples 9 to 13 are different from example 1 in that the molar percentages of the crosslinking agent in the two monomers are changed in step S3, and other steps are substantially the same as those in example 1 and are not repeated herein; the molar percentages of the cross-linking agent in examples 9-13 based on the two monomers are shown in the following table:
item
|
The cross-linking agent is in mol percent of the two monomers
|
Example 1
|
0.1%
|
Example 9
|
0.01%
|
Example 10
|
0.05%
|
Example 11
|
0.15%
|
Example 12
|
0.2%
|
Example 13
|
0.3% |
According to experiments, when the molar percentage of the cross-linking agent in the two monomers is changed within the range of 0.01-0.3%, the mechanical strength of the force-induced color-changing self-repairing elastic film is improved and the force-induced color-changing sensitivity is improved along with the increase of the molar percentage of the cross-linking agent in the two monomers, but the flexibility of the polymer film is reduced to some extent.
When the molar percentage of the cross-linking agent in the two monomers is less than 0.01%, the content of the linear polymer in the elastic film is high, the force-induced color change sensitivity is low, and the polymer film can be subjected to color change only by applying high stress.
When the molar percentage of the cross-linking agent in the two monomers is more than 0.3%, the prepared polymer film has poor flexibility and high hardness, and cannot be used as a flexible substrate.
Examples 14 to 18
Examples 14 to 18 and comparative examples 3 to 4 are different from example 1 in that the mole percentages of the initiator in the two monomers are changed in step S3, and other steps are substantially the same as those in example 1 and are not repeated herein; the mole percentages of the initiator based on the two monomers in examples 14-18 are shown in the following table:
item
|
The initiator is in mole percent of the two monomers
|
Example 1
|
1%
|
Example 14
|
0.5%
|
Example 15
|
1.5%
|
Example 16
|
2%
|
Example 17
|
2.5%
|
Example 18
|
3%
|
Comparative example 3
|
0.2%
|
Comparative example 4
|
4% |
According to experiments, when the mole percentage of the initiator in the two monomers is changed within the range of 0.5-3%, the mechanical property of the force-induced color-changing self-repairing elastic film is improved and the force-induced color-changing sensitivity is improved along with the increase of the mole percentage of the initiator in the two monomers.
When the initiator accounts for 0.2 percent of the two monomers in mole percent, the mechanical property of the force-induced discoloration self-repairing elastic film is reduced to some extent and the force-induced discoloration sensitivity is reduced because the initiator is less and the polymerization reaction rate is slower.
When the initiator accounts for 4% of the two monomers in mole percentage, the initiator is used in a large amount, the polymerization reaction rate is high, and the generated heat in a short time is large, so that bubbles are easily generated inside the polymer film, the mechanical property of the polymer film is reduced, and the force-induced discoloration sensitivity and the self-repairing property are influenced.
Examples 19 to 26
The difference between the embodiments 19-26 and embodiment 1 is that in step S3, the preset temperature and the reaction time are different, and other steps are substantially the same as those in embodiment 1, and are not repeated herein; the preset temperatures and reaction times described in examples 19-26 are shown in the following table:
according to experiments, the reaction rate of the copolymerization reaction is correspondingly increased along with the increase of the preset temperature, and after the same reaction time, the mechanical strength of the force-induced color-changing self-repairing elastic film is higher, the force-induced color-changing sensitivity is improved, but the flexibility is reduced to some extent. Under the same preset temperature, the mechanical strength of the force-induced color-changing self-repairing elastic film is enhanced along with the extension of the reaction time, the force-induced color-changing sensitivity is improved, but the flexibility is also reduced.
Examples 27 to 44
Examples 27 to 44 differ from examples 1 to 18 in that the spiropyran derivative prepared in step S1 has a structure HO-SP1-OH, and the rest is substantially the same as examples 1 to 18 and is not repeated herein.
Examples 45 to 62
Examples 45 to 62 differ from examples 1 to 18 in that the spiropyran derivative prepared in step S1 has a structure HO-SP3-OH, which is otherwise substantially the same as example 1 and will not be described herein again.
Examples 63 to 80
Examples 63 to 80 differ from examples 1 to 18 in that the rhodamine derivative prepared in step S1 has a structure HO — Rh — OH, which is substantially the same as example 1, and will not be described herein again.
As can be seen from the comparative examples 1 to 80, the performance of the self-healing elastic membrane prepared by using spiropyran derivatives of different structures HO-SP1-OH, HO-SP2-OH, HO-SP3-OH or rhodamine derivatives HO-Rh-OH is not greatly different.
Examples 81 to 160
Examples 81 to 160 differ from examples 1 to 80 in that the structural formula of the crosslinking agent prepared in step S2 is different and substantially the same, and the description thereof is omitted:
in step S2 of the above embodiment, the isocyanoethyl methacrylate may be replaced with one of isocyanoethyl acrylate and 3-isopropenyl- α, α -dimethylbenzyl isocyanate.
The dibutyltin dilaurate can be replaced by one of tetraphenyltin, stannous octoate and dimethyltin.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.