CN111269373B - Preparation method of remodelable shape memory elastomer based on eutectic - Google Patents

Preparation method of remodelable shape memory elastomer based on eutectic Download PDF

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CN111269373B
CN111269373B CN202010087918.XA CN202010087918A CN111269373B CN 111269373 B CN111269373 B CN 111269373B CN 202010087918 A CN202010087918 A CN 202010087918A CN 111269373 B CN111269373 B CN 111269373B
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eutectic
elastomer
copolyester
prepolymer
shape memory
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CN111269373A (en
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潘鹏举
袁文华
单国荣
包永忠
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Quzhou Research Institute of Zhejiang University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
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    • C08F2/00—Processes of polymerisation
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
    • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
    • C08F299/04—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyesters
    • C08F299/0407—Processes of polymerisation
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    • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
    • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
    • C08F299/04—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyesters
    • C08F299/0485—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyesters from polyesters with side or terminal unsaturations
    • C08F299/0492—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyesters from polyesters with side or terminal unsaturations the unsaturation being in acrylic or methacrylic groups
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
    • C08G18/4269—Lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/4266—Polycondensates having carboxylic or carbonic ester groups in the main chain prepared from hydroxycarboxylic acids and/or lactones
    • C08G18/4269—Lactones
    • C08G18/4277—Caprolactone and/or substituted caprolactone
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2280/00—Compositions for creating shape memory

Abstract

The invention relates to a shape memory elastomer technology, and aims to provide a preparation method of a remodelable shape memory elastomer based on eutectic. The method comprises the following steps: preparing linear aliphatic polylactone diol by a ring-opening polymerization method, dissolving two or more than two kinds of polylactone diol and an ester exchange catalyst in a proper amount of solvent, and removing the solvent after uniform dispersion; heating the mixture for reaction; the eutectic copolyester diol obtained by the reaction and polyfunctional group isocyanate are subjected to chemical crosslinking to prepare an elastomer; or eutectic copolyester diol is modified into prepolymer with double bond modified end, and the prepolymer is chemically cross-linked with multifunctional mercapto compound to prepare the elastomer. The invention realizes simple preparation of copolyester with different sequence structures and melting points, and is suitable for mass production. The elastomer with different thermal transition temperatures and high crystallinity is obtained, and the application requirement is further facilitated. The product has excellent shape memory performance at respective deformation temperature, the fixation rate and the recovery rate are close to 100 percent, and the product can meet the requirements of different occasions.

Description

Preparation method of remodelable shape memory elastomer based on eutectic
Technical Field
The invention relates to the technical field of shape memory elastomers, in particular to eutectic-based chemical crosslinking copolyester with high-temperature remolding performance and low-temperature shape memory effect and a preparation method thereof.
Background
As a class of intelligent materials, shape memory polymers can undergo shape changes under the action of external stimuli such as heat, light, electricity, magnetism, solvents and the like. Therefore, the polymer material has been developed to be a polymer material which attracts much attention in recent years, and is expected to play a great role in the fields of biomedicine, intelligent textiles, packaging, soft robots, aerospace and the like. The thermal transition temperature is one of the most important parameters of shape memory materials and determines the applications of such materials. The thermal transition temperature generally refers to the glass transition temperature of an amorphous polymer or the melting point of a crystalline polymer. When the thermal transition temperature is close to the body temperature of a human body, the shape memory polymer can play a great application potential in the fields of biological medicines, medical equipment and the like.
Copolymerization methods are often used to effectively control the thermal transition temperature of the polymer. The Lendlein group prepared shape memory polymers with different melting points and mechanical properties in 2001 by constructing networks of oligo (epsilon-caprolactone) dimethacrylate and n-butyl acrylate in different ratios (Lendlein et al, proc. natl. acad. sci.,2001,98, 842). The Luo topic group synthesized thermoplastic shape memory polymers of different sequence structures and glass transition temperatures by living radical copolymerization in 2013 (Luo et al, adv. Mater.,2013,25, 743).
To simplify the cumbersome copolymerization process, a dynamically reversible bond exchange reaction can be used to generate copolymers of different sequence structures in situ. Telen topic group copolymers with different sequence structures and thermal behavior were prepared by transamidation of polyamide 11 and polyamide 12 under high temperature extrusion conditions in 2016 (Telen et al, Macromolecules,2016,49, 876). At the same time, such dynamic exchange reactions allow the topological structure of the thermosetting material to be rearranged and impart to the material many properties, such as self-repairability, recyclability and removability (chinese patent document CN 105037702B).
Nevertheless, the above-mentioned crystalline shape memory polymers still have a limitation in that the introduction of copolymerized units causes a significant decrease in crystallinity. On the one hand, the crystalline phase acts as a reversible phase of the shape memory polymer, the reduction of which is detrimental to the realisation of the shape memory effect. On the other hand, a copolymer with low crystallinity reduces the modulus and thermal stability of the material.
Therefore, it is necessary to provide a novel remodelable shape memory elastomer and a preparation method thereof.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a preparation method of a remodelable shape memory elastomer based on eutectic. The shape memory elastomer with different thermal transition temperatures and high crystallinity is prepared by the ester exchange reaction of eutectic polyester diol.
In order to solve the technical problem, the solution of the invention is as follows:
a preparation method of a remodelable shape memory elastomer based on eutectic is provided, which comprises the following steps:
(1) preparing at least two linear aliphatic polylactone diols with 4-16 carbon atoms by a ring-opening polymerization method, wherein the linear aliphatic polylactone diols are used as eutectic polyester diols;
(2) dissolving two or more than two eutectic polyester diols and an ester exchange catalyst in a proper amount of solvent, wherein the ester exchange catalyst accounts for 0.2-2.0 wt% of the total mass of the eutectic polyester diols; after uniform dispersion, removing the solvent; then heating the mixture to 100-150 ℃, and reacting for 0.5-6 h to obtain eutectic copolyester glycol;
(3) the memory elastomer is prepared according to any one of the following schemes:
the first scheme is as follows: the eutectic copolyester glycol and polyfunctional isocyanate are subjected to chemical crosslinking to prepare the elastomer, and the preparation method specifically comprises the following steps:
adding eutectic copolyester glycol and polyfunctional group isocyanate into dimethylformamide and fully dissolving, wherein the molar ratio of hydroxyl groups to isocyanate groups in the mixed solution is 1:1, and the concentration of the eutectic copolyester glycol is 0.5 g/ml; pouring the mixed solution into a mold, reacting at 80 ℃ for 10h to finish curing, demolding, and drying in a vacuum oven at 40 ℃ for 24 h; alternatively, the first and second electrodes may be,
scheme II: eutectic copolyester diol is firstly modified into a prepolymer with a modified terminal double bond, and then the prepolymer is chemically crosslinked with a polyfunctional group mercapto compound to prepare an elastomer; the method specifically comprises the following steps:
(3.1) preparation of terminal double bond modified copolyester
Drying eutectic copolyester glycol, gradually adding anhydrous toluene serving as a solvent until the solution is clear, and then adding triethylamine serving as an acid-binding agent; dropwise adding acryloyl chloride under the ice-water bath condition to ensure that the molar ratio of triethylamine, the acryloyl chloride and eutectic copolyester glycol in a reaction system is 1: 3: 1; after being mixed evenly, the mixture reacts for 10 hours at the temperature of 20 ℃; precipitating with n-hexane, filtering reaction product, and repeatedly washing with anhydrous methanol for at least 3 times; finally, drying for 24 hours at 40 ℃ in vacuum to obtain a prepolymer, namely the copolyester modified by the double bonds at the tail end;
(3.2) preparation of elastomer by crosslinking with polyfunctional mercapto Compound
Adding the prepolymer, a crosslinking agent, a photoinitiator and a transesterification catalyst into dimethylformamide and fully dissolving, wherein the concentration of the prepolymer in the solution is 0.5 g/ml; the photoinitiator accounts for 0.5 wt% of the total weight of the prepolymer, and the ester exchange catalyst accounts for 2 wt% of the total weight of the prepolymer; controlling the dosage of the prepolymer and the crosslinking agent to ensure that the molar ratio of double bonds to sulfydryl is 1: 1; transferring the mixed solution into a quartz glass mold, and irradiating for 10min under 365nm ultraviolet light to realize curing; and (4) after demolding, vacuum drying at 40 ℃ for 24h to obtain the eutectic-based remolding shape memory elastomer material.
In the invention, the eutectic polyester diol in the step (1) has a molecular weight of 2000-8000 g/mol, and is selected from any one of the following substances: poly (. delta. -valerolactone) (PVL), poly (. epsilon. -caprolactone) (PCL), poly (. omega. -pentadecanolide) (PPDL).
In the present invention, the transesterification catalyst in the step (2) is selected from an organic base, or a metal salt of tin, magnesium, zinc, calcium, cobalt.
Preferably, the transesterification catalyst in step (2) is selected from 1,5, 7-triazabicyclo [4.4.0]Dec-5-ene (TBD) or Zinc acetate [ Zn (ac)2]。
In the present invention, the cross-linking agent in the first embodiment of step (3) is selected from any one of the following: triphenylmethane Triisocyanate (TTI), hexamethylene diisocyanate biuret (PHDI), isophorone diisocyanate (IPDI) trimer.
In the present invention, the cross-linking agent in the second embodiment of step (3) is selected from any one of the following: trimethylolpropane tris (3-mercaptopropionate) (TMMP), pentaerythritol tetrakis (2-mercaptoacetate), pentaerythritol tetrakis (3-mercaptopropionate) (PTME).
In the present invention, the photoinitiator in the second scheme of step (3) is 1-hydroxycyclohexyl benzophenone (UV-184).
In the invention, the thermal transition temperature (melting point) of the remoldable shape memory elastomer is 20-80 ℃, and the remoldable temperature is 100-150 ℃.
Description of the inventive principles:
in the present invention, the eutectic-based remodelable shape memory elastomer undergoes two transesterification reactions. Wherein, the first time, two or more eutectic aliphatic polyester diols generate recombination among copolymerization units through deep ester exchange reaction between active hydroxyl at the tail end of a polymer chain and an ester bond between chains under the action of an ester exchange catalyst, and generate a copolymer with a random sequence structure in situ. The random copolymer has a high crystallinity because different copolymerized units can coexist in the same crystal lattice in the eutecticeable polymer. And the second time, reversible ester exchange reaction is carried out in the polymer network after chemical crosslinking in the presence of an ester exchange catalyst, so that network topology rearrangement is realized, and the material has a remodeling characteristic.
In the invention, the remodelable shape memory elastomer based on eutectic has the effects of shape memory and shape re-plasticity. The principle of the elastic body for realizing the shape memory is that the elastic body is heated to be above a melting point, the activity of chain segments is increased, and external force is applied to deform; cooling to below the melting point under constant external force, freezing the chain segment, storing elastic energy, and fixing the temporary shape after the external force is removed; the temperature is raised again to above the melting point, the elastic energy is released and the shape returns to a permanent shape. The principle behind the achievement of superplastic properties in elastomers is that the dynamically reversible nature of the transesterification reaction effects a rearrangement of the polymer network topology to accommodate the external force and gradually relax, eventually becoming a new permanent shape under that external force.
In the invention, the shape remodeling process of the eutectic-based remodelable shape memory elastomer comprises the following steps: and (3) placing the elastomer with the permanent shape of the shape A in a remolding temperature environment, and keeping for 0.5-6 h under the action of constant external force to obtain the elastomer with the permanent shape of the shape B.
The shape memory process comprises the following steps: (1) placing the elastomer with the permanent shape of A or B in an environment with a melting point above and a remodeling temperature below, and deforming the elastomer into a temporary shape C under the action of external force; (2) placing the elastomer fixed into the temporary shape C in an environment below the melting point to realize the fixation of the temporary shape; (3) the elastomer having the temporary shape C is placed in an environment above the melting point and below the remodeling temperature to effect recovery of the elastomer from the temporary shape C to the permanent shape a or B.
Compared with the prior art, the invention has the following technical advantages:
(1) the invention realizes simple preparation of copolyester with different sequence structures and melting points by blending and heating two or more than two polyester diols and utilizing ester exchange reaction, and is suitable for mass production.
(2) The invention utilizes the characteristic that different comonomers of eutectic copolyester diol can be crystallized in the same crystal lattice to obtain the elastomer with different thermal transition temperatures and high crystallinity, thereby being more beneficial to application requirements.
(3) The eutectic copolyester elastomer has excellent shape memory performance at respective deformation temperature, and the fixation rate and the recovery rate are close to 100 percent, so that the eutectic copolyester elastomer can meet the requirements of different occasions.
(4) The eutectic copolyester elastomer has permanent shape remolding characteristic at high temperature, and can meet the requirement of equipment with more complicated deformation.
(5) The eutectic copolyester elastomer is biodegradable, and meanwhile, the copolymerization structure accelerates the degradation rate, reduces the pressure for environmental pollution, and is green and ecological.
Drawings
FIG. 1 is a melting behavior diagram of examples 5,7, 15 and 16.
FIG. 2 is a WAXD graph showing the crystal structures of examples 5,7, 15 and 16
Figure 3 is the shape memory display of example 5.
Figure 4 is the shape memory display of example 7.
FIG. 5 is a shape memory display of example 15.
FIG. 6 is a shape memory display of example 16.
FIG. 7 is a graph of the shape memory cycle test of example 5.
FIG. 8 is a graph of stress relaxation curves at different temperatures for example 5.
Fig. 9 is a simulated display of the deformation of the stent of example 5.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
(1) Preparation of polyester diols
The polyester diol is prepared by a ring-opening polymerization method, and specific steps can refer to the content described in Chinese patent document CN 107022070B.
Table 1: initiator, monomer, catalyst, reaction temperature and reaction time adopted in preparation of homopolyester 1-4
Figure BDA0002382664240000051
Note: sn (Oct)2Is stannous octoate.
(2) Preparation of eutectic copolyester diols
The method for preparing eutectic copolyester glycol by ester exchange comprises the following specific steps: uniformly mixing two or more eutectic polyester diols and an ester exchange catalyst in a proper amount of solvent, wherein the ester exchange catalyst accounts for 0.2-2.0 wt% of the total mass of the eutectic polyester diols; after the solvent is removed, the mixture is heated to 100-150 ℃ and reacts for 0.5-6 hours to complete the ester exchange reaction, and eutectic copolyester glycol is obtained.
Table 2: homopolyester composition, molecular weight and charge ratio, catalyst type and dosage, ester exchange reaction temperature and time in copolyester 1-14 preparation
Figure BDA0002382664240000052
(3) Preparation of elastomers
Elastomers can be prepared by crosslinking in two ways.
In method one, an elastomer is prepared by a chemical crosslinking reaction of a eutectic copolyester glycol with a polyfunctional isocyanate; the specific exemplary steps are:
dissolving eutectic copolyester glycol and PHDI in dimethylformamide, wherein the molar ratio of hydroxyl to isocyanate group in the mixed solution is 1:1, and the concentration of the eutectic copolyester glycol is 0.5 g/ml; after being mixed evenly, the solution is poured into a mould and reacts for 10 hours at 80 ℃ to finish the solidification. After demoulding, the mixture is dried in a vacuum oven for 24 hours at 40 ℃. The first transesterification catalyst can catalyze the crosslinking reaction and continue to function during the permanent shape remodeling stage.
Table 3: examples 1-3 preparation of elastomer by Process one raw Material, crosslinking agent, type and amount of catalyst, reaction temperature and time
Figure BDA0002382664240000061
In the second method, eutectic copolyester diol is first modified into prepolymer with double bond modified end and then chemically crosslinked with polyfunctional mercapto compound to prepare elastomer. Exemplary specific steps include the following two steps:
(1) preparation of terminal double bond modified copolyester
Drying eutectic copolyester glycol, gradually adding anhydrous toluene serving as a solvent until the solution is clear, and then adding triethylamine serving as an acid-binding agent; dropwise adding acryloyl chloride under the ice-water bath condition to ensure that the molar ratio of triethylamine, the acryloyl chloride and eutectic copolyester glycol in a reaction system is 1: 3: 1; after being mixed evenly, the mixture reacts for 10 hours at the temperature of 20 ℃; precipitating with n-hexane, filtering reaction product, and repeatedly washing with anhydrous methanol for at least 3 times; finally, drying for 24 hours at the temperature of 40 ℃ in vacuum to obtain a prepolymer, namely the copolyester modified by the terminal double bond.
(2) Preparation of elastomer by crosslinking with polyfunctional mercapto compound
Adding the prepolymer, a cross-linking agent, a photoinitiator UV-184 and a transesterification catalyst into dimethylformamide and fully dissolving, wherein the concentration of the prepolymer in the solution is 0.5 g/ml; the photoinitiator accounts for 0.5 wt% of the total weight of the prepolymer, and the ester exchange catalyst accounts for 2 wt% of the total weight of the prepolymer; controlling the dosage of the prepolymer and the crosslinking agent to ensure that the molar ratio of double bonds to sulfydryl is 1: 1; transferring the mixed solution into a quartz glass mold, and irradiating for 10min under 365nm ultraviolet light to realize curing; and (4) after demolding, vacuum drying at 40 ℃ for 24h to obtain the eutectic-based remolding shape memory elastomer material.
Table 4: examples 4 to 18 preparation of elastomer by Process two raw materials, crosslinking agent, type and amount of catalyst, and wavelength and time of ultraviolet light irradiation
Figure BDA0002382664240000071
In the present invention, the eutectic-based remodelable shape memory elastomer can be characterized by the following analytical instruments, including:
DSC test: the thermal properties of the transesterified copolymer and its elastomer were analyzed by NETZSCH 214Polyma DSC (NETZSCH, Germany) at a ramp rate of 10 deg.C/min.
WAXD test: the crystalline structure of the polymer was analyzed using an X 'Pert PRO instrument (X' Pert PRO, PANalytical) and the sample film was scanned using Ni filtered CuK α radiation (λ ═ 0.154 nm). And calculating the crystallinity (X) from the WAXD curvec)。
Figure BDA0002382664240000081
Where A isaRepresents the area of the non-oriented phase, AcRepresenting the area of the amorphous phase.
And DMA test: the elastomer shape memory behavior was quantitatively characterized using DMA Q850(TA instruments). The sample strip is clamped in a tensile fixture and raised to the deformation temperature at a rate to mark the strain epsilon of the sample strip at that timeo(ii) a The temperature is then lowered to a shape-fixing temperature under constant stress at a rate and isothermally held for a period of time, marking the strain of the specimen at that time as εload(ii) a Removing the external force again, and marking the strain of the sample strip at the moment to be epsilonunload(ii) a Finally heating to the recovery temperature to obtain a sample strain mark epsilonrec. The shape fixation ratio (R) of the sample can be quantitatively calculated by using the following formulaf) And shape recovery ratio (R)r)。
Figure BDA0002382664240000082
Figure BDA0002382664240000083
And (3) stress relaxation test: the elastomer stress relaxation behavior was quantitatively characterized using DMA Q850(TA instruments). The sample bar was clamped in a tensile fixture, the temperature was set to the stress relaxation temperature, a constant stress was applied to the sample bar and held at that temperature, the test was run over time, and the change in internal stress of the sample bar was recorded.
And (3) analyzing experimental data:
from DSC and WAXD analysis results (fig. 1, fig. 2 and table 5), eutectic copolyester elastomers prepared from PCL and PPDL or PVL and PCL after transesterification have different melting points, but all have crystallinity of 30% or more. As can be seen from fig. 1 and 2, the blend ratio of the selected eutectic polyester diol at the time of transesterification is closer to 5: the lower the melting point of the resulting eutectic copolyester elastomer, and exhibiting the cocrystallized structure of a random copolyester (examples 5,7, 15, 16). With the increase of the molecular weight of the selected eutectic polyester diol, the melting point of the eutectic copolyester elastomer is gradually increased, and the change of the crystallinity is not obvious (examples 5-7); in addition, the increase of the content of the ester exchange catalyst, the increase of the ester exchange temperature and the extension of the ester exchange time can promote the generation of the copolyester with a random structure, and the lower the melting point of the obtained eutectic copolyester elastomer is, but the crystallinity is only slightly reduced (examples 5, 8-13); the different selected transesterification catalysts have similar catalytic effects, and the obtained eutectic copolyester elastomers have similar melting points and crystallinity (examples 5 and 14); the various crosslinking modes chosen do not affect the properties of the eutectic copolyester elastomer (examples 1, 2, 4, examples 3, 5, 18). The above results indicate that eutectic copolyester diols with random sequence structure can be obtained from two or more eutectic aliphatic polyester diols by transesterification reaction, and the melting point of eutectic copolyester can be reasonably regulated and controlled based on the variables such as the composition, molecular weight, mixing ratio, ester exchange catalyst content, reaction temperature and time of polyester diols, so that elastomers with different thermal transition temperatures and high crystallinity can be prepared.
Table 5: examples 1-18 gel content, melting Point, crystallinity, deformation temperature, immobilization Rate, recovery, remodeling temperature and time of the elastomer
Figure BDA0002382664240000091
As can be seen from the shape memory DMA test results and the display pictures (FIGS. 3-7 and Table 5), the copolyester elastomers with different thermal transition temperatures all exhibited excellent shape memory properties (R) at the respective deformation temperaturesf>97％，Rr>97%) and the strip with a rectangular permanent shape was temporarily fixed in a wavy form and quickly returned to the permanent shape after the temperature was raised above the melting point. The results show that the eutectic copolyester elastomer prepared under different ester exchange conditions can meet the deformation temperature requirements of different application occasions. As in example 5, good shape fixation and recovery were achieved around body temperature, and application to medical devices for human body was expected.
As can be seen from the quantitative test results of stress relaxation (FIG. 8), example 5 showed stress relaxation behavior at 120-150 ℃. And the stress relaxation speed is accelerated along with the rise of the temperature, and the stress is completely relaxed within 40min at 150 ℃.
As shown in fig. 9, the permanent shape a of the sample of example 5 is a grid shape, and it is placed in an environment of a remodeling temperature of 130 ℃, end-to-end crimped and left for 2 hours to complete stress relaxation. The mold was removed and the sample was observed to retain the permanent shape B in the form of an expanded stent (12 mm diameter). Then continuously deforming at 37 ℃, fixing at 0 ℃ to be in a temporary shape C contraction stent shape (the diameter is 7.5mm), finally heating to 37 ℃ to return to a permanent shape B expansion stent shape (the diameter is 12mm), and finishing the working process of the simulated vascular stent in the human body. The results show that the eutectic copolyester elastomer can combine and display permanent shape remodeling characteristics and shape memory effects, and is expected to be applied to biomedical equipment.
Finally, it should be noted that the above-mentioned list is only a specific embodiment of the present invention. It is obvious that the present invention is not limited to the above embodiments, but many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.

Claims (8)

1. A preparation method of a remodelable shape memory elastomer based on eutectic is characterized by comprising the following steps:
(1) preparing at least two linear aliphatic polylactone diols with 4-16 carbon atoms by a ring-opening polymerization method, wherein the linear aliphatic polylactone diols are used as eutectic polyester diols; the molecular weight of the eutectic polyester diol is 2000-8000 g/mol;
(2) dissolving two or more than two eutectic polyester diols and an ester exchange catalyst in a proper amount of solvent, wherein the ester exchange catalyst accounts for 0.2-2.0 wt% of the total mass of the eutectic polyester diols; after uniform dispersion, removing the solvent; then heating the mixture to 100-150 ℃, and reacting for 0.5-6 h to obtain eutectic copolyester glycol;
(3) the memory elastomer is prepared according to any one of the following schemes:
the first scheme is as follows: the eutectic copolyester glycol and polyfunctional isocyanate used as a crosslinking agent are subjected to chemical crosslinking to prepare the elastomer, and the preparation method specifically comprises the following steps:
adding eutectic copolyester glycol and polyfunctional group isocyanate into dimethylformamide and fully dissolving, wherein the molar ratio of hydroxyl groups to isocyanate groups in the mixed solution is 1:1, and the concentration of the eutectic copolyester glycol is 0.5 g/ml; pouring the mixed solution into a mold, reacting at 80 ℃ for 10h to finish curing, demolding, and drying in a vacuum oven at 40 ℃ for 24 h; alternatively, the first and second electrodes may be,
scheme II: eutectic copolyester diol is firstly modified into a prepolymer with a modified terminal double bond, and then the prepolymer is chemically crosslinked with a polyfunctional group mercapto compound serving as a crosslinking agent to prepare an elastomer; the method specifically comprises the following steps:
(3.1) preparation of terminal double bond modified copolyester
Drying eutectic copolyester glycol, gradually adding anhydrous toluene serving as a solvent until the solution is clear, and then adding triethylamine serving as an acid-binding agent; dropwise adding acryloyl chloride under the ice-water bath condition to ensure that the molar ratio of triethylamine, the acryloyl chloride and eutectic copolyester glycol in a reaction system is 1: 3: 1; after being mixed evenly, the mixture reacts for 10 hours at the temperature of 20 ℃; precipitating with n-hexane, filtering reaction product, and repeatedly washing with anhydrous methanol for at least 3 times; finally, drying for 24 hours at 40 ℃ in vacuum to obtain a prepolymer, namely the copolyester modified by the double bonds at the tail end;
(3.2) preparation of elastomer by crosslinking with polyfunctional mercapto Compound as crosslinking agent
Adding the prepolymer, a crosslinking agent, a photoinitiator and a transesterification catalyst into dimethylformamide and fully dissolving, wherein the concentration of the prepolymer in the solution is 0.5 g/ml; the photoinitiator accounts for 0.5 wt% of the total weight of the prepolymer, and the ester exchange catalyst accounts for 2 wt% of the total weight of the prepolymer; controlling the dosage of the prepolymer and the crosslinking agent to ensure that the molar ratio of double bonds to sulfydryl is 1: 1; transferring the mixed solution into a quartz glass mold, and irradiating for 10min under 365nm ultraviolet light to realize curing; and (4) after demolding, vacuum drying at 40 ℃ for 24h to obtain the eutectic-based remolding shape memory elastomer material.
2. The method according to claim 1, wherein the eutectic polyester diol in step (1) is selected from any one of the following: poly (delta-valerolactone), poly (epsilon-caprolactone), poly (omega-pentadecanolide).
3. The method according to claim 1, wherein the transesterification catalyst in step (2) is selected from an organic base, or a metal salt of tin, magnesium, zinc, calcium, cobalt.
4. The process of claim 1, wherein the transesterification catalyst in step (2) is selected from 1,5, 7-triazabicyclo [ 4.4.0%]Dec-5-ene (TBD) or Zinc acetate [ Zn (ac)2]。
5. The method according to claim 1, wherein the cross-linking agent in the first embodiment of step (3) is selected from any one of the following: triphenylmethane triisocyanate, hexamethylene diisocyanate biuret, isophorone diisocyanate trimer.
6. The method according to claim 1, wherein the cross-linking agent in the second embodiment of step (3) is selected from any one of the following: trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), pentaerythritol tetrakis (3-mercaptopropionate).
7. The method of claim 1, wherein the photoinitiator in scheme two in step (3) is 1-hydroxycyclohexyl benzophenone.
8. The method of claim 1, wherein the remodelable shape memory elastomer has a melting point as a thermal transition temperature in the range of 20 to 80 ℃; the remodeling temperature is 100-150 ℃.
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