CN116496518A - Dynamic boric acid ester bond toughened polyvinyl alcohol film and preparation method thereof - Google Patents
Dynamic boric acid ester bond toughened polyvinyl alcohol film and preparation method thereof Download PDFInfo
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- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 96
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 96
- 239000004327 boric acid Substances 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 16
- 238000000137 annealing Methods 0.000 claims abstract description 9
- ZMUANTVDGHVAHS-UHFFFAOYSA-N OBOB(O)C1=CC=CC=C1 Chemical compound OBOB(O)C1=CC=CC=C1 ZMUANTVDGHVAHS-UHFFFAOYSA-N 0.000 claims abstract description 5
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 12
- 238000004090 dissolution Methods 0.000 claims description 8
- 239000003960 organic solvent Substances 0.000 claims description 8
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 4
- 238000006136 alcoholysis reaction Methods 0.000 claims description 3
- 238000006116 polymerization reaction Methods 0.000 claims description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 2
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 24
- 238000004132 cross linking Methods 0.000 abstract description 7
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 6
- 239000001257 hydrogen Substances 0.000 abstract description 6
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 abstract description 6
- 238000002425 crystallisation Methods 0.000 abstract description 4
- 230000008025 crystallization Effects 0.000 abstract description 4
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 4
- 230000009471 action Effects 0.000 abstract description 3
- 230000002776 aggregation Effects 0.000 abstract description 3
- 238000004220 aggregation Methods 0.000 abstract description 3
- 230000002441 reversible effect Effects 0.000 abstract description 3
- 238000006482 condensation reaction Methods 0.000 abstract description 2
- 230000018044 dehydration Effects 0.000 abstract description 2
- 238000006297 dehydration reaction Methods 0.000 abstract description 2
- 239000010408 film Substances 0.000 description 55
- 239000000243 solution Substances 0.000 description 28
- 239000002253 acid Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
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- 239000010409 thin film Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 229920002988 biodegradable polymer Polymers 0.000 description 1
- 239000004621 biodegradable polymer Substances 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 150000002009 diols Chemical class 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
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- 238000005457 optimization Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- HXITXNWTGFUOAU-UHFFFAOYSA-N phenylboronic acid Chemical class OB(O)C1=CC=CC=C1 HXITXNWTGFUOAU-UHFFFAOYSA-N 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/55—Boron-containing compounds
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- Chemical Kinetics & Catalysis (AREA)
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- Polymers & Plastics (AREA)
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Abstract
The invention discloses a dynamic boric acid ester bond toughened polyvinyl alcohol film and a preparation method thereof. The toughened polyvinyl alcohol film prepared by the solution reaction-annealing heat treatment method is mainly characterized by comprising the following steps: the preparation method comprises the steps that the phenyldiboronic acid and the hydroxyl of the polyvinyl alcohol are subjected to dehydration condensation reaction to form a dynamic reversible crosslinking structure, so that the hydrogen bonding action among the molecular chains of the polyvinyl alcohol is weakened, and the crystallization of the polyvinyl alcohol is inhibited; during annealing heat treatment, dynamic bond exchange can occur at high temperature to promote aggregation of the cross-linking agent phenyldiboronic acid, a stacked structure with pi-pi conjugated benzene rings is formed, and toughening of the polyvinyl alcohol film is achieved. The polyvinyl alcohol film based on dynamic boric acid ester bond crosslinking has good mechanical property and self-repairing property, and the preparation method is simple.
Description
Technical Field
The invention belongs to the technical field of polyvinyl alcohol films, and particularly relates to a dynamic borate ester bond toughened polyvinyl alcohol film and a preparation method thereof.
Background
Polyvinyl alcohol (PVA) is a biodegradable polymer, can be decomposed under natural conditions to obtain a nontoxic product, and cannot cause white pollution; meanwhile, the method can be produced in a large scale by a non-petroleum route, and has remarkable economic and ecological values. The polyvinyl alcohol has a simple and regular structure, a large number of hydroxyl groups can form various hydrogen bonds among molecular chains and improve the crystallinity of the polyvinyl alcohol, the structure can give the polyvinyl alcohol enough mechanical strength, the toughness of the material is limited, the material is strong and brittle, the elongation at break is extremely low, flexible applications such as bending and torsion are difficult to realize, and the application scene is difficult to widen, so the polyvinyl alcohol needs to be toughened and modified on the premise of keeping the certain strength of the material.
The traditional method for toughening the polyvinyl alcohol mainly comprises physical toughening modification and chemical toughening modification. Physical toughening is realized by introducing a modifier to prepare a composite material or optimizing network structure design to adjust the crystallization state, intermolecular interaction and the like of PVA, wherein the toughening is realized by introducing materials with different structures, properties and the like from PVA into matrix resin, and introducing new interaction or forming new molecular aggregation state while changing hydrogen bonds between PVA molecular chains; the latter adjusts the preparation process of the optimization system through strategies such as freezing casting, mechanical training, salting out, solvent replacement, and the like, so that the PVA toughening effect is achieved by the network system with a directional molecular arrangement mode, a multi-scale network, a layered structure, and the like. The chemical toughening is a modification method for improving the performance of PVA by introducing certain substances to chemically react with polyvinyl alcohol, changing the molecular chain structure and the connection mode of the substances, a uniform and compact polymer network is formed in the chemically modified PVA, and meanwhile, the introduced covalent bonds change the intermolecular interaction, so that the mechanical performance of PVA materials can be greatly improved, and aldehyde and carboxylic acid/anhydride molecules are two substances most commonly used for PVA chemical toughening modification. However, physical toughening and chemical toughening are both advantageous and disadvantageous, and it is still a challenge to achieve toughening of polyvinyl alcohol by taking into account the advantages of conventional physical and chemical toughening modification.
(phenyl) boronic acids have the affinity of specifically recognizing cis-dihydroxy groups and can be selectively combined with diols to form dynamic boronic acid ester bonds. Under certain conditions, the dynamic borate bond can realize reversible fracture-recombination of chemical bonds through hydrolysis/re-esterification or transesterification among borate bonds, and the molecular structure of the material is changed. By utilizing the dynamic reversibility of the boric acid ester bond, the boric acid ester bond can be introduced into the polyvinyl alcohol, so that the self-repairing, remodelling and other performances of the material can be endowed, and the toughness of the polyvinyl alcohol film can be realized.
Disclosure of Invention
In order to overcome the defects of the traditional PVA physical modification and chemical modification methods, the invention aims to provide a polyvinyl alcohol film toughened by dynamic boric acid ester bonds and a preparation method thereof. The method is simple to operate, the reaction is easy to control, and a novel strategy for toughening the polyvinyl alcohol film by utilizing the dynamic boric acid ester bond is innovatively provided.
In order to achieve the technical purpose and achieve the technical effect, the invention is realized by the following technical scheme:
a preparation method of a polyvinyl alcohol film toughened by dynamic boric acid ester bonds comprises the following steps:
respectively dissolving polyvinyl alcohol and a cross-linking agent in an organic solvent, uniformly mixing at room temperature, drying, annealing, and cooling to obtain the dynamic boric acid ester bond toughened polyvinyl alcohol film;
the cross-linking agent is phenyldiboronic acid, and the structure of the cross-linking agent is shown as structural formulas I-III:
wherein R is 1 ＝-H、-F、-OH、-CH 3 、-CH 2 OCH 3 At least one of (a) and (b); r is R 2 ＝-H、-F、-OH、-CH 3 、-CH 2 OCH 3 At least one of (a) and (b); r is R 3 ＝-H、-CH 3 At least one of them.
Preferably, the alcoholysis degree of the polyvinyl alcohol is 88-99% and the polymerization degree is 1700-2000.
Preferably, the organic solvent is at least one of dimethyl sulfoxide, methanol, chloroform, glycerol, N-dimethylformamide and N, N-dimethylacetamide.
Preferably, the ratio of the polyvinyl alcohol to the organic solvent is 1-10 wt%, the dissolution temperature is 60-90 ℃, and the dissolution time is 1-3 hours.
Preferably, the ratio of the cross-linking agent to the organic solvent is 0.1-1 wt%, the dissolution temperature is 20-40 ℃, and the dissolution time is 0.5-2 h.
Preferably, the mass ratio of the cross-linking agent to the polyvinyl alcohol is 1-7wt%; the mixing time of the cross-linking agent and the polyvinyl alcohol is 2 hours, and the mixing temperature is 15-35 ℃.
Preferably, the temperature of the drying step is 60-90 ℃ and the time is 10-24 h.
Preferably, the temperature of the annealing step is 90-120 ℃ and the time is 20 min-2 h.
The dynamic boric acid ester bond toughened polyvinyl alcohol film prepared by the method.
By adopting the technical scheme, the invention has the following advantages and beneficial effects:
1. the invention forms a dynamic reversible crosslinking network by utilizing the hydroxy dehydration condensation reaction of the phenyldiboronic acid and the PVA chain, weakens the hydrogen bond between molecular chains and weakens the crystallization capability of the PVA; in the subsequent heat treatment process, the dynamic borate bond is heated to induce association type bond exchange to form a benzene ring pi-pi conjugated aggregation structure, and the structure can be used as a sacrificial bond to dissipate energy in the stretching process so as to improve the toughness of the crosslinked polyvinyl alcohol film.
2. The polyvinyl alcohol film prepared by the invention adopts dynamic covalent bond crosslinking, and can realize recycling and remolding processing of the film; meanwhile, the biodegradability of the polyvinyl alcohol film does not cause environmental pollution.
3. The invention introduces dynamic boric acid ester bonds to toughen the conventional polymer materials, takes advantages of the traditional physical or chemical modification method into account, and provides a new strategy for toughen the polymer materials.
4. The polyvinyl alcohol film based on dynamic boric acid ester bond crosslinking has good mechanical property and self-repairing property, and the preparation method is simple.
Drawings
FIG. 1 is a schematic diagram of a conjugated structure formed by stacking benzene rings.
FIG. 2 is an ultraviolet fluorescence real object diagram, wherein FIG. 2a is an ultraviolet fluorescence real object diagram of a sample which is not annealed; FIG. 2b is an ultraviolet fluorescence real image of a sample annealed at 120℃for 1 h.
FIG. 3 shows the fluorescence absorption spectra of the thin film after heat treatment of pure PVA at different temperatures for 1 h.
FIG. 4 is a graph showing fluorescence absorption spectra of thin films after heat treatment at different temperatures when the amount of the crosslinking agent added is 1%.
FIG. 5 is a graph showing the self-repairing property of the film when the amount of the crosslinking agent added is 3%.
Detailed Description
The present invention will be described in further detail with reference to preferred embodiments, so that those skilled in the art can better understand the technical aspects of the present invention. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The invention provides a dynamic boric acid ester bond toughened polyvinyl alcohol film and a preparation method thereof. In the present invention, preferably, the polyvinyl alcohol has a polymerization degree of 1700 and an alcoholysis degree of 88%.
Example 1
(1) 1.8g of polyvinyl alcohol solid is weighed and dissolved in 58.2g of dimethyl sulfoxide, and the mixture is stirred for 2 hours at 80 ℃ to obtain polyvinyl alcohol solution;
(2) Weighing 0.1g of terephthalyl acid powder, dissolving in 9.9g of dimethyl sulfoxide, and stirring at normal temperature for 2h to obtain terephthalyl acid solution;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 1%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain a polyvinyl alcohol film;
(4) And (3) placing the film obtained in the step (3) in a vacuum oven for heat treatment, wherein the heating temperature is 120 ℃, the heating time is 20min, and cooling to room temperature to obtain the toughened polyvinyl alcohol film.
Example 2
Step (1) and step (2) are the same as in example 1;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 3%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain a polyvinyl alcohol film;
(4) And (3) placing the film obtained in the step (3) in a vacuum oven for heat treatment, wherein the heating temperature is 120 ℃, the heating time is 1h, and cooling to room temperature to obtain the toughened polyvinyl alcohol film.
Example 3
Step (1) and step (2) are the same as in example 1;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 7%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain a polyvinyl alcohol film;
(4) And (3) placing the film obtained in the step (3) in a vacuum oven for heat treatment, wherein the heating temperature is 100 ℃, the heating time is 1h, and cooling to room temperature to obtain the toughened polyvinyl alcohol film.
Example 4
(1) 1.8g of polyvinyl alcohol solid is weighed and dissolved in 58.2g of dimethyl sulfoxide, and the mixture is stirred for 2 hours at 80 ℃ to obtain polyvinyl alcohol solution;
(2) Pouring the solution into a glass vessel, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain an uncrosslinked pure polyvinyl alcohol film;
(3) And (3) placing the film in the step (2) in a vacuum oven for heat treatment, wherein the heating temperature is 120 ℃, the heating time is 1h, and cooling to room temperature to obtain the heat-treated pure polyvinyl alcohol film.
Comparative example 1
(1) 1.8g of polyvinyl alcohol solid is weighed and dissolved in 58.2g of dimethyl sulfoxide, and the mixture is stirred for 2 hours at 80 ℃ to obtain polyvinyl alcohol solution;
(2) Weighing 0.1g of terephthalyl acid powder, dissolving in 9.9g of dimethyl sulfoxide, and stirring at normal temperature for 2h to obtain terephthalyl acid solution;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 1%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain the polyvinyl alcohol film.
Comparative example 2
Step (1) and step (2) are the same as comparative example 1;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 3%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain the polyvinyl alcohol film.
Comparative example 3
Step (1) and step (2) are the same as comparative example 1;
(3) Adding the solution obtained in the step (2) into the solution obtained in the step (1) according to the mass ratio of the terephthalyl acid to the polyvinyl alcohol being 7%, and stirring for 2 hours at room temperature; pouring the uniformly mixed solution into a glass dish, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain the polyvinyl alcohol film.
Comparative example 4
(1) 1.8g of polyvinyl alcohol solid is weighed and dissolved in 58.2g of dimethyl sulfoxide, and the mixture is stirred for 2 hours at 80 ℃ to obtain polyvinyl alcohol solution;
(2) Pouring the solution into a glass vessel, drying the solution in an oven at 80 ℃ for 13 hours, and removing the solvent to obtain an uncrosslinked pure polyvinyl alcohol film;
the polyvinyl alcohol films prepared in examples and comparative examples were prepared into standard bars, and their tensile strength and elongation at break were tested by a universal tester, and the test data results are shown in table 1.
Table 1 shows the mechanical properties of examples and comparative examples, in terms of tensile yield strength sigma in MPa, elongation at break epsilon in% and toughness tau in MJ/m 3 。
Table 1 mechanical properties of examples and comparative examples
FIG. 2a is an ultraviolet fluorescence real object diagram of a sample which is not subjected to annealing treatment, wherein the samples are respectively 0, 1%, 3%, 5% and 7% of the cross-linking agent from left to right; FIG. 2b is an ultraviolet fluorescence real object diagram of a sample annealed at 120 ℃ for 1h, and samples with the addition amounts of the cross-linking agent of 0%, 1%, 3%, 5% and 7% are respectively from left to right. As can be seen from the figure, compared with the initial film, the film has more obvious fluorescence phenomenon after annealing heat treatment for 1h at 120 ℃, the introduction of the cross-linking agent damages the structural regularity and crystallinity of the pure PVA, however, the cross-linked film can still emit stronger fluorescence, and the formation of the benzene ring conjugated structure can be preliminarily proved.
As can be seen from a comparison of FIGS. 3 and 4, the pure PVA film has a small peak at about 325nm only, corresponding to n-pi of C=O * The transition and the hydrogen bonding action in the structure jointly cause that the pure PVA film also has certain fluorescence phenomenon. For the cross-linked film after heat treatment, an obvious benzene ring conjugated absorption peak appears at 250-300nm, the intensity of the absorption peak is obviously enhanced along with the increase of the heat treatment temperature, and the exchange and rearrangement of dynamic bonds are generated in the annealing heat treatment process, so that a benzene ring stacked conjugated structure is gradually formed, the effect is enhanced, and the fluorescence absorption of the film in the wavelength range is obviously increased.
FIG. 5 is a graph showing the self-repairing property of a film, wherein a new borate bond cross-linked structure can be formed at the interface of the cut film under the action of a small amount of water, the yield strength of the film gradually increases along with the prolongation of the healing time, the yield strength of the film can reach 90MPa when the healing time is 24 hours, the self-repairing efficiency reaches about 84%, and the excellent self-repairing property of the film is realized. The self-healing efficiency is defined as the ratio of the yield strength of the film after healing to the yield strength of the film before healing.
As can be seen from the data in table 1, the pure polyvinyl alcohol film exhibits typical hard and brittle characteristics, and has high mechanical strength but extremely high brittleness and extremely low elongation at break; during heat treatment, the motion capability of the molecular chain in the polyvinyl alcohol is enhanced, the system is further crystallized, so that the mechanical strength of the pure polyvinyl alcohol film is obviously improved, and the film still shows poor toughness. The introduction of terephthalyl acid into polyvinyl alcohol consumes a large amount of hydroxyl groups in the main chain and forms a dynamic cross-linked network structure based on boric acid ester bonds. The reduction of the hydrogen bond of the system and the formation of a cross-linked network reduce the crystallization capacity of the system, which is not beneficial to the improvement of the mechanical strength; the mechanical strength can be improved to a certain extent by improving the crosslinking degree, so that the strength of the polyvinyl alcohol film tends to be increased and then reduced under the influence of the crystallinity and the crosslinking degree along with the improvement of the content of the introduced crosslinking agent. In addition, as is apparent from comparative examples 2 and 2, the strength and elongation at break of the film after heat treatment are significantly increased, and the toughening effect is remarkable, because during the subsequent heat treatment, the dynamic borate ester bonds undergo association type bond exchange to form pi-pi stacked conjugated structures (as shown in fig. 1), which can dissipate energy during stretching as sacrificial bonds to improve the toughness of the crosslinked polyvinyl alcohol film. The invention provides a polyvinyl alcohol film toughened by dynamic borate bonds and a preparation method thereof, which remarkably improve the mechanical property of the polyvinyl alcohol film, have simple and easily controlled preparation process, realize the toughening of the conventional polymer material by introducing the dynamic borate bonds and provide a new strategy for the toughening of the conventional polymer material.
The preferred embodiments of the invention disclosed above are merely helpful in explaining the invention. The preferred embodiments are not exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best understand and utilize the invention. The invention is limited only by the claims and the full scope and equivalents thereof.
Claims (9)
1. The preparation method of the polyvinyl alcohol film toughened by the dynamic boric acid ester bonds is characterized by comprising the following steps of:
respectively dissolving polyvinyl alcohol and a cross-linking agent in an organic solvent, uniformly mixing at room temperature, drying, annealing, and cooling to obtain the dynamic boric acid ester bond toughened polyvinyl alcohol film;
the cross-linking agent is phenyldiboronic acid, and the structure of the cross-linking agent is shown as structural formulas I-III:
wherein R is 1 ＝-H、-F、-OH、-CH 3 、-CH 2 OCH 3 At least one of (a) and (b); r is R 2 ＝-H、-F、-OH、-CH 3 、-CH 2 OCH 3 At least one of (a) and (b); r is R 3 ＝-H、-CH 3 At least one of them.
2. The method according to claim 1, wherein the polyvinyl alcohol has an alcoholysis degree of 88 to 99% and a polymerization degree of 1700 to 2000.
3. The method according to claim 1, wherein the organic solvent is at least one of dimethyl sulfoxide, methanol, chloroform, glycerol, N-dimethylformamide, and N, N-dimethylacetamide.
4. The process according to claim 1, wherein the ratio of polyvinyl alcohol to organic solvent is 1 to 10wt%, the dissolution temperature is 60 to 90 ℃ and the dissolution time is 1 to 3 hours.
5. The process according to claim 1, wherein the ratio of the crosslinking agent to the organic solvent is 0.1 to 1wt%, the dissolution temperature is 20 to 40 ℃ and the dissolution time is 0.5 to 2 hours.
6. The preparation method according to claim 1, wherein the mass ratio of the crosslinking agent to the polyvinyl alcohol is 1 to 7wt%; the mixing time of the cross-linking agent and the polyvinyl alcohol is 2 hours, and the mixing temperature is 15-35 ℃.
7. The method according to claim 1, wherein the drying step is carried out at a temperature of 60 to 90 ℃ for a time of 10 to 24 hours.
8. The method according to claim 1, wherein the annealing step is performed at a temperature of 90 to 120 ℃ for 20min to 2h.
9. A dynamic borate ester bond toughened polyvinyl alcohol film prepared according to any one of claims 1 to 8.
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| CN202310211505.1A CN116496518A (en) | 2023-03-07 | 2023-03-07 | Dynamic boric acid ester bond toughened polyvinyl alcohol film and preparation method thereof |
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| CN202310211505.1A CN116496518A (en) | 2023-03-07 | 2023-03-07 | Dynamic boric acid ester bond toughened polyvinyl alcohol film and preparation method thereof |
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