CN115894919A - Cross-linked gradient bicrystal phase polyurethane and preparation method and application thereof - Google Patents
Cross-linked gradient bicrystal phase polyurethane and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a cross-linked gradient bicrystal phase polyurethane and a preparation method and application thereof, relating to the technical field of bidirectional shape memory materials. The invention utilizes thermodynamic phase separation among different prepolymers to obtain a dual-crystal phase; and by utilizing the characteristic of limited penetration depth of ultraviolet light, the difference of the cross-linking degree in the thickness direction is obtained while polyurethane curing is realized by the ultraviolet light, and a cross-linking gradient is introduced to enter a bicrystal phase polyurethane system. The invention realizes reversible reversal of the trend of the driving strain controlled by the stretching programming strain along with the temperature change, which is not possessed by the traditional semi-crystal two-way shape memory material: drive strain at low programming strain (100%) becomes smaller hot and larger cold; while at high programming strain (200%) the drive strain becomes larger hot and smaller cold. The unique two-way shape memory effect makes the application of the cross-linked gradient bicrystal phase polyurethane in the fields of intelligent drivers, brakes and the like more controllable and intelligent.
Description
Technical Field
The invention relates to the technical field of bidirectional shape memory materials, in particular to cross-linked gradient bicrystal phase polyurethane and a preparation method and application thereof.
Background
Compared with a unidirectional shape memory material, the semi-crystalline bidirectional shape memory material has wide application prospect in the fields of intelligent drivers, actuators and soft robots due to the reversible change of the shape of the material under the external non-contact stimulation and the simplicity of a synthesis process and reprogramming shape change.
The classical strategy for implementing a semi-crystalline two-way shape memory material is the two-phase (high temperature and low temperature) and thermo-mechanical pre-programming reported by Andreas Lendlein topic group. In particular, at high temperatures (T) p ) Enabling the semi-crystalline polymer to be in a rubber state, applying force through thermomechanical preprogramming to deform the material, enabling molecular chains to be oriented along the force direction, reducing the temperature until the semi-crystalline material is crystallized to fix the deformed shape, and then removing the external force; when the material again raises the temperature (T) high ) Melting the low-temperature crystalline phase, and compressing the high-temperature crystalline phase to store internal stress due to the fact that the entropy elastic material is shortened; when the temperature is further reduced to be lower than the crystallization temperature (T) of the low-temperature crystalline phase low ) The low-temperature crystal phase has a tendency of recrystallization, and the internal stress pre-stored in the high-temperature crystal phase is released to make the low-temperature crystal phase directionally crystallize and the shape is elongated. Reversible storage of internal stress of high-temperature crystalline phase to reversible directional crystallization of low-temperature crystalline phase is the basis of reversible change of shape, so that the material is in T high And T low Triggering a reversible change in shape. The above is the classical strain expression of the semi-crystalline two-way shape memory material, that is, the driving strain in the semi-crystalline reversible shape memory polymer is in negative correlation (shrinkage under heat and elongation under cold) with the temperature change due to the entropy elasticity of the polymer and the oriented crystallization under the internal stress storage and release mechanism. Chen et al (Chen, G.; dong, J.; xu, X.; zou, W.; jin, B.; peng, W.; ZHao, Q.; xie, T.; zheng, N., converting t-way flap memory effect through a dynamic covalent bond. Journal of Materials Chemistry A2022, 10 (19), 10350-10354) controlled the direction of crystallization by stress relaxation through dynamic covalent bondsThe material driving strain and the temperature show positive correlation (hot extension and cold contraction). At present, reversible transformation for realizing the relationship between the two driving strains and the temperature change based on the same two-way shape memory material is not reported.
Disclosure of Invention
In view of the above, the present invention aims to provide a cross-linked gradient bi-crystalline phase polyurethane, and a preparation method and applications thereof. The cross-linked gradient bicrystal phase polyurethane prepared by the invention has a unique two-way shape memory effect, and when the pre-programmed strain is 100%, the driving strain change is in negative correlation with the temperature; at a preprogrammed strain of 200% strain, the change in drive strain is positively correlated with temperature.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of cross-linked gradient bicrystal phase polyurethane, which comprises the following steps:
mixing poly (omega-pentadecanolide) diol, allyl isocyanate, a first catalyst and a first organic solvent to perform a first addition reaction to obtain poly (omega-pentadecanolide) diallyl formamide;
mixing poly (epsilon-caprolactone) dihydric alcohol, allyl isocyanate, a second catalyst and a second organic solvent to perform a second addition reaction to obtain poly (epsilon-caprolactone) diallyl formamide;
and mixing the poly (omega-pentadecanolide) diallyl formamide, a third organic solvent, a mercapto group crosslinking agent, a photoinitiator and poly (epsilon-caprolactone) diallyl formamide or polyethylene glycol diacrylate, carrying out first ultraviolet radiation curing on the upper surface of the obtained mixed solution, and then carrying out second ultraviolet radiation curing on the lower surface of the mixed solution to obtain the crosslinking gradient bicrystal phase polyurethane.
Preferably, the preparation method of the poly (omega-pentadecanolide) glycol comprises the following steps:
mixing omega-pentadecanolide, 1, 8-octanediol and the third catalyst to perform ring-opening polymerization reaction to obtain poly (omega-pentadecanolide) diol.
Preferably, the third catalyst is 1,5, 7-triazabicyclo (4.4.0) dec-5-ene; the mass of the third catalyst is 1-3% of the sum of the mass of the omega-pentadecanolide, the mass of the 1, 8-octanediol and the mass of the third catalyst, and the mass of the 1, 8-octanediol is 2-3.5% of the sum of the mass of the omega-pentadecanolide, the mass of the 1, 8-octanediol and the mass of the third catalyst; the temperature of the ring-opening polymerization reaction is 90-120 ℃, and the time is 48-72 h.
Preferably, the first and second catalysts are dibutyltin dilaurate; the temperature of the first addition reaction and the second addition reaction is independently 80-90 ℃, and the time is independently 3.5-6 h; the first addition reaction and the second addition reaction are both carried out under a protective atmosphere.
Preferably, in the first addition reaction, the molar ratio of the poly (omega-pentadecanolide) diol to the allyl isocyanate is 1; the mass of the first catalyst is 0.5-2% of that of the poly (omega-pentadecanolide) diol.
Preferably, in the second addition reaction, the molar ratio of the poly (epsilon-caprolactone) diol to the allyl isocyanate is 1; the mass of the second catalyst is 0.5-2% of that of the poly (epsilon-caprolactone) diol.
Preferably, the mercapto crosslinking agent is trimethylolpropane tris (3-mercaptopropionate); the mass of the poly (omega-pentadecanolide) diallyl formamide is 5-20% of the sum of the mass of the poly (omega-pentadecanolide) diallyl formamide and the mass of the poly (epsilon-caprolactone) diallyl formamide or the sum of the mass of the poly (omega-pentadecanolide) diallyl formamide and the mass of the polyethylene glycol diacrylate; the ratio of the total molar amount of double bonds in the poly (omega-pentadecanolide) diallyl formamide and the poly (epsilon-caprolactone) diallyl formamide or the polyethylene glycol diacrylate to the molar amount of sulfydryl in the sulfydryl crosslinking agent is 3.
Preferably, the power of an ultraviolet light source used in the first ultraviolet radiation curing and the second ultraviolet radiation curing is 250W, the wavelength of the light source is 315-450 nm, and the distance between the ultraviolet light source and the upper surface or the lower surface of the mixed solution is independently 5-10 cm; the first ultraviolet irradiation curing time is 5-10 min, the second ultraviolet irradiation curing time is 2-8 min, and the first ultraviolet irradiation curing time is longer than or equal to the second ultraviolet irradiation curing time.
The invention provides the cross-linking gradient bicrystal phase polyurethane prepared by the preparation method of the technical scheme.
The invention provides application of the cross-linked gradient bicrystal phase polyurethane in an intelligent driver or an intelligent brake.
The invention provides a preparation method of cross-linked gradient bicrystal phase polyurethane, which comprises the following steps: mixing poly (omega-pentadecanolide) diol, allyl isocyanate, a first catalyst and a first organic solvent to perform a first addition reaction to obtain poly (omega-pentadecanolide) diallyl formamide; mixing poly (epsilon-caprolactone) diol, allyl isocyanate, a second catalyst and a second organic solvent to perform a second addition reaction to obtain poly (epsilon-caprolactone) diallyl formamide; and mixing the poly (omega-pentadecanolide) diallyl formamide, a third organic solvent, a mercapto-group crosslinking agent and a photoinitiator with poly (epsilon-caprolactone) diallyl formamide or polyethylene glycol diacrylate, carrying out first ultraviolet irradiation curing on the upper surface of the obtained mixed solution, and then carrying out second ultraviolet irradiation curing on the lower surface of the mixed solution to obtain the crosslinking gradient bicrystal phase polyurethane. The invention utilizes the classic strategy of reversible shape memory polyurethane synthesis and takes poly (omega-pentadecanolide) phase as high T m The phase (i.e. high-temperature crystalline phase) takes poly (epsilon-caprolactone) phase or polyethylene glycol phase as low T m Phase (i.e. low temperature crystalline phase) in which a high T is obtained by thermodynamic phase separation between poly (. Omega. -pentadecanolide) and poly (. Epsilon. -caprolactone) or polyethylene glycol segments m Phase storage internal stress to low T m Phase reversible directional crystallization to realize reversible change of shape; the method utilizes the characteristic of limited penetration depth of ultraviolet light, obtains the difference of crosslinking degrees in the thickness direction while realizing polyurethane curing by the ultraviolet light, namely introduces a crosslinking gradient into a bicrystal phase polyurethane system to obtain crosslinking gradient bicrystal phase polyurethane; the introduction of the cross-linking gradient achieves a distribution of crystallinity gradient controlled by the stretching programming, resulting in a gradient distribution of stored internal stress when programming the shape change, which allows, under the same one-step thermal stretching programming,when the pre-programmed strain is 100%, the strain is detected at T high Lower decrease, T low Lower increase, i.e. the driving strain change is inversely related to temperature, which is the same as the conventional strategy; while at a pre-programmed strain of 200% strain, the memory of the internal stress gradient is revealed, the shape change is represented by a reversible bending drive, the strain of which is at T high Lower increase, T low The lower decrease, i.e., the change in drive strain is positively correlated to temperature.
The invention realizes the reversible reversal of the trend of the drive strain controlled by the tensile programming strain along with the temperature change, which is not possessed by the traditional semi-crystalline two-way shape memory material: drive strain at low programming strain (100%) becomes smaller hot and larger cold; while at high programming strains (200%) the drive strain becomes larger hot and smaller cold. The unique two-way shape memory effect makes the application of the cross-linked gradient bicrystal phase polyurethane in the fields of intelligent drivers, brakes and the like more controllable and intelligent.
Drawings
FIG. 1 is a graph of reversible (two-way) shape memory cycling test at 100% programmed strain for the cross-linked gradient twin-phase polyurethane prepared in example 1;
FIG. 2 is a graph of the reversible (two-way) shape memory cycle at 200% programmed strain for the cross-linked gradient twin-phase polyurethane prepared in example 1;
FIG. 3 is a graph of the reversible (two-way) shape memory cycle at 200% programmed strain for the non-crosslinked gradient polyurethane prepared in comparative example 1.
Detailed Description
The invention provides a preparation method of cross-linked gradient bicrystal phase polyurethane, which comprises the following steps:
mixing poly (omega-pentadecanolide) diol, allyl isocyanate, a first catalyst and a first organic solvent to perform a first addition reaction to obtain poly (omega-pentadecanolide) diallyl formamide;
mixing poly (epsilon-caprolactone) dihydric alcohol, allyl isocyanate, a second catalyst and a second organic solvent to perform a second addition reaction to obtain poly (epsilon-caprolactone) diallyl formamide;
and mixing the poly (omega-pentadecanolide) diallyl formamide, a third organic solvent, a mercapto group crosslinking agent, a photoinitiator and poly (epsilon-caprolactone) diallyl formamide or polyethylene glycol diacrylate, carrying out first ultraviolet radiation curing on the upper surface of the obtained mixed solution, and then carrying out second ultraviolet radiation curing on the lower surface of the mixed solution to obtain the crosslinking gradient bicrystal phase polyurethane.
In the present invention, the starting materials are all commercially available products well known to those skilled in the art unless otherwise specified.
The preparation method comprises the steps of mixing poly (omega-pentadecanolide) dihydric alcohol, allyl isocyanate, a first catalyst and a first organic solvent to carry out a first addition reaction to obtain poly (omega-pentadecanolide) diallyl formamide. In the present invention, the method for preparing the poly (ω -pentadecanolide) glycol preferably includes: mixing omega-pentadecanolide, 1, 8-octanediol and the third catalyst to perform ring-opening polymerization reaction to obtain poly (omega-pentadecanolide) diol. In the present invention, the third catalyst is preferably 1,5, 7-triazabicyclo (4.4.0) dec-5-ene (TBD); the mass of the third catalyst is preferably 1 to 3%, more preferably 2 to 3% of the sum of the mass of ω -pentadecanolide, 1, 8-octanediol and the third catalyst. In the present invention, the mass of the 1, 8-octanediol is preferably 2 to 3.5%, more preferably 2.5 to 3.3%, of the sum of the mass of the ω -pentadecanolide, the mass of the 1, 8-octanediol, and the mass of the third catalyst. In the present invention, the temperature of the ring-opening polymerization reaction is preferably 90 to 120 ℃, more preferably 100 to 110 ℃, and the time is preferably 48 to 72 hours, more preferably 48 to 60 hours; the ring-opening polymerization reaction is preferably carried out under stirring. In the present invention, the reaction formula of the ring-opening polymerization reaction is shown as formula A:
after the ring-opening polymerization reaction is completed, the ring-opening polymerization reaction liquid obtained is preferably subjected to post-treatment, and the post-treatment method is preferably as follows: dissolving the ring-opening polymerization reaction solution in excessive chloroform, then precipitating in normal hexane, and filtering to obtain a precipitate; and drying the precipitate to obtain the poly (omega-pentadecanolide) diol.
In the present invention, the molar ratio of the poly (ω -pentadecanolide) diol to the allyl isocyanate is preferably 1; the first catalyst is preferably dibutyltin dilaurate (DBTDL), and the mass of the first catalyst is preferably 0.5 to 2%, more preferably 1%, of the mass of the poly (ω -pentadecanolide) diol. In the invention, the first organic solvent is preferably DMF, and the addition amount of the first organic solvent is not particularly required, so that the smooth reaction can be ensured. In the present invention, the poly (ω -pentadecanolide) diol, the allyl isocyanate, the first catalyst, and the first organic solvent are preferably added in the order of: the poly (omega-pentadecanolide) diol is added first, and then the first organic solvent, the allyl isocyanate and the first catalyst are sequentially added. In the present invention, the temperature of the first addition reaction is preferably 80 to 90 ℃, more preferably 85 to 90 ℃, and the time is preferably 3.5 to 6 hours, more preferably 4 to 5 hours; the first addition reaction is preferably carried out under a protective atmosphere, preferably nitrogen; the first addition reaction is preferably carried out under stirring. In the invention, the first addition reaction is specifically an addition reaction of an isocyanate group in allyl isocyanate and a terminal hydroxyl group in poly (omega-pentadecanolide) diol; the reaction formula of the addition reaction is shown as formula B:
after the first addition reaction is completed, the first addition reaction liquid is preferably precipitated in n-heptane, and the obtained precipitate is sequentially washed with n-heptane and dried to obtain poly (omega-pentadecanolide) diallylcarboxamide.
The poly (epsilon-caprolactone) diol, allyl isocyanate, a second catalyst and a second organic solvent are mixed for a second addition reaction to obtain the poly (epsilon-caprolactone) diallyl formamide. The poly (epsilon-caprolactone) diol is not particularly required by the invention, and the poly (epsilon-caprolactone) diol well known to a person skilled in the art can be adopted, and in the embodiment of the invention, the poly (epsilon-caprolactone) diol is selected from poly (epsilon-caprolactone) diol produced by new materials science and technology limited in the polymer recycling industry in Hunan, and has a structure shown as a poly (epsilon-caprolactone) diol in a formula C; the number average molecular weight of the poly (epsilon-caprolactone) diol is preferably 2000 to 3000, and specifically may be 2000 or 3000. In the present invention, the molar ratio of the poly (epsilon-caprolactone) diol to the allyl isocyanate is preferably 1; the second catalyst is preferably dibutyltin dilaurate (DBTDL), and the mass of the second catalyst is preferably 0.5-2%, more preferably 1%, of the mass of the poly (epsilon-caprolactone) diol. In the invention, the second organic solvent is preferably DMF, and the invention has no special requirement on the dosage of the second organic solvent and ensures that the reaction is smoothly carried out. In the present invention, the temperature of the second addition reaction is preferably 80 to 90 ℃, more preferably 85 to 90 ℃, and the time is preferably 3.5 to 6 hours, more preferably 4 to 5 hours; the second addition reaction is preferably carried out under a protective atmosphere, preferably nitrogen; the second addition reaction is preferably carried out under stirring. In the invention, the second addition reaction is specifically an addition reaction of an isocyanate group in allyl isocyanate and a terminal hydroxyl group in poly (epsilon-caprolactone) diol; the reaction formula of the addition reaction is shown as formula C:
after the second addition reaction is completed, the second addition reaction liquid is preferably precipitated in n-heptane, and the obtained precipitate is sequentially washed and dried with n-heptane to obtain the poly (epsilon-caprolactone) diallyl formamide.
After poly (omega-pentadecanolide) diallyl formamide and poly (epsilon-caprolactone) diallyl formamide are obtained, the poly (omega-pentadecanolide) diallyl formamide, poly (epsilon-caprolactone) diallyl formamide, a third organic solvent, a mercapto crosslinking agent and a photoinitiator are mixed, the upper surface of the obtained mixed solution is subjected to first ultraviolet radiation curing, and then the lower surface of the mixed solution is subjected to second ultraviolet radiation curing to obtain the crosslinking gradient bicrystal phase polyurethane. In the present invention, the mass of the poly (ω -pentadecanolide) diallylcarboxamide is preferably 5 to 20%, more preferably 10 to 15% of the sum of the masses of poly (ω -pentadecanolide) diallylcarboxamide and poly (ε -caprolactone) diallylcarboxamide. In the present invention, the mercapto crosslinking agent is preferably trimethylolpropane tris (3-mercaptopropionate) (TMPMP), and the ratio of the total molar amount of double bonds in the poly (ω -pentadecanolide) diallylformamide to the poly (e-caprolactone) diallylformamide to the molar amount of mercapto groups in the mercapto crosslinking agent is preferably 3 to 3, more preferably 1. In the present invention, the photoinitiator is preferably a photoinitiator 651, and the mass of the photoinitiator is preferably 1 to 5%, preferably 2 to 3%, of the sum of the masses of poly (ω -pentadecanolide) diallylcarboxamide and poly (ε -caprolactone) diallylcarboxamide. In the present invention, the third organic solvent is preferably trichloroethane, and the amount of the third organic solvent used in the present invention is not particularly limited, and the reaction raw material may be sufficiently dissolved. In the invention, preferably, the poly (omega-pentadecanolide) diallyl formamide and the poly (epsilon-caprolactone) diallyl formamide are dissolved in a third organic solvent, and then the mercapto crosslinking agent and the photoinitiator are sequentially added to obtain a mixed solution.
In the present invention, the specific operations of the first ultraviolet radiation curing and the second ultraviolet radiation curing are preferably: and pouring the mixed liquid into an open culture dish, placing the upper surface (namely the open surface of the culture dish) of the obtained mixed liquid under an ultraviolet lamp for first ultraviolet irradiation curing, then inverting the culture dish, and then performing second ultraviolet irradiation curing on the lower surface (namely the bottom surface of the culture dish). In the invention, the power of the ultraviolet light source used for the first ultraviolet radiation curing and the second ultraviolet radiation curing is preferably 250W; the wavelength of the light source is preferably 315-450 nm, and more preferably 365nm; the distance between the ultraviolet light source and the upper surface or the lower surface of the mixed solution is preferably 5-10 cm independently; the time for the first ultraviolet radiation curing is preferably 5 to 10min, the time for the second ultraviolet radiation curing is preferably 2 to 8min, and the time for the first ultraviolet radiation curing is preferably greater than or equal to the time for the second ultraviolet radiation curing, in the embodiment of the present invention, the time for the first ultraviolet radiation curing is further preferably 5 to 6min, and the time for the second ultraviolet radiation curing is further preferably 3 to 4min. In the ultraviolet curing process, terminal double bonds in poly (omega-pentadecanolide) diallyl formamide and poly (epsilon-caprolactone) diallyl formamide and sulfydryl of a sulfydryl crosslinking agent respectively carry out ultraviolet light triggered click reaction in the presence of a photoinitiator, so that polymer network curing is realized, and a bicrystal phase polyurethane structure consisting of a poly (omega-pentadecanolide) chain and a poly (epsilon-caprolactone) chain is formed; meanwhile, the penetration depth of ultraviolet rays is limited, incomplete curing in the thickness direction is obtained by regulating and controlling curing process parameters, namely, the difference of the cross-linking degree in the thickness direction is obtained, and then a cross-linking gradient is introduced into the bicrystal phase polyurethane to obtain the cross-linking gradient bicrystal phase polyurethane.
Or, mixing the poly (omega-pentadecanolide) diallyl formamide, the polyethylene glycol diacrylate, the third organic solvent, the mercapto crosslinking agent and the photoinitiator, performing first ultraviolet irradiation curing on the upper surface of the obtained mixed solution, and performing second ultraviolet irradiation curing on the lower surface of the mixed solution to obtain the crosslinking gradient bicrystal phase polyurethane. In the present invention, the number average molecular weight of the polyethylene glycol diacrylate is preferably 2000 to 3000, and specifically may be 2000 or 3000; the mass of the poly (omega-pentadecanolide) diallyl formamide is preferably 5-20%, more preferably 10-15% of the sum of the masses of the poly (omega-pentadecanolide) diallyl formamide and the polyethylene glycol diacrylate. In the present invention, the mercapto crosslinking agent is preferably trimethylolpropane tris (3-mercaptopropionate) (TMPMP), and the ratio of the total molar amount of double bonds in the poly (ω -pentadecanolide) diallylformamide and polyethylene glycol diacrylate to the molar amount of mercapto groups in the mercapto crosslinking agent is preferably 3. In the present invention, the photoinitiator is preferably a photoinitiator 651, and the mass of the photoinitiator is preferably 1 to 5% of the sum of the mass of the poly (omega-pentadecanolide) diallylformamide and the mass of the polyethylene glycol diacrylate. In the present invention, the third organic solvent is preferably trichloroethane, and the amount of the third organic solvent used in the present invention is not particularly limited, and the reaction raw material may be sufficiently dissolved. In the present invention, the specific operation and conditions of the first ultraviolet radiation curing and the second ultraviolet radiation curing are the same as those in the above technical solution, and are not described herein again.
The invention provides the cross-linking gradient bicrystal phase polyurethane prepared by the preparation method of the technical scheme. The invention utilizes thermodynamic phase separation among different prepolymers to obtain a bicrystal phase, and particularly provides the bicrystal phase polyurethane which has a poly (omega-pentadecanolide) phase and a poly (epsilon-caprolactone) phase or has the poly (omega-pentadecanolide) phase and a polyethylene glycol phase. Wherein, the phase separation obtains poly (omega-pentadecanolide) phase with the melting transformation range of 86-93 ℃ and the crystallization transformation range of 69-78 ℃; the poly (epsilon-caprolactone) phase has a melt transition range of 30 to 53 ℃ (Mn = 3000) or 25 to 48 ℃ (Mn = 2000), and a crystallographic transition range of 12 to 26.5 ℃ (Mn = 3000) or 8 to 24 ℃ (Mn = 2000); the polyethylene glycol phase has a melting transition range of 49 to 58 ℃ (Mn = 3000) or 45 to 53 ℃ (Mn = 2000), and a crystallization transition range of 29 to 38 ℃ (Mn = 3000) or 23 to 33 ℃ (Mn = 2000). The thermodynamic properties of the phases obtained are obtained by DSC analysis, the heating rate is 5 ℃/min, and the cooling rate is 10 ℃/min.
Meanwhile, the bicrystal phase polyurethane has a cross-linking gradient in the thickness direction, and for the cross-linking gradient bicrystal phase polyurethane, the introduction of the cross-linking gradient realizes the distribution of crystallinity gradient controlled by stretching programming, thereby causing the gradient distribution of storage internal stress when the programmed shape changes, and detecting the strain at T when the pre-programmed strain is 100% under the same one-step thermal stretching programming high Lower decrease, T low Lower increase, i.e. the driving strain change is inversely related to temperature, which is the same as the conventional strategy; while at 200% strain at the pre-programmed strain, the memory of the internal stress gradient is revealed, the shape change appears as a reversible bending drive with strain at T high Lower increase, T low The lower decrease, i.e., the change in drive strain is positively correlated to temperature. Wherein, T p Is selected to be higher than the high temperatureThe melt transition range of the crystalline phase (poly (ω -pentadecanolide) phase); t is high The selection of (A) is required to be between the melting transition of a high-temperature crystalline phase and a low-temperature crystalline phase (a poly (epsilon-caprolactone) phase or a polyethylene glycol phase); t is low Is selected below the crystalline transition range of the low temperature crystalline phase.
In the invention, the two-way shape memory effect of the cross-linked gradient bi-crystal phase polyurethane is embodied by the following method: the shape memory cycle curve was obtained under DMAQ800, and the implementation procedure was: the cross-linking gradient bicrystal phase polyurethane sample is processed at T p Preserving heat at the temperature, and then stretching to 100% strain or 200% strain; the resulting tensile specimen was then cooled to T low Preserving the temperature; the stress on the specimen is then removed, at T low Preserving heat at the temperature; the sample is subsequently brought to T under stress-free conditions high Temperature at T high Maintaining the temperature at a temperature and then cooling the mixture to T again under a stress-free condition low Carrying out heat preservation at T high -T low The above-described heating and cooling cycle is repeated. In the present invention, T p Preferably 95 ℃ T high Preferably 60 ℃ T low Preferably 0 ℃; the heating rate and the cooling rate are both preferably 5 ℃/min, and the heat preservation time is preferably 10min.
The invention provides application of the cross-linked gradient bicrystal phase polyurethane in an intelligent driver and a brake. The cross-linked gradient bicrystal phase polyurethane prepared by the invention has a unique two-way shape memory effect, and when the pre-programmed strain is 100%, the driving strain change is in negative correlation with the temperature; at a preprogrammed strain of 200% strain, the change in drive strain is positively correlated to temperature. The unique two-way shape memory effect enables the application of the cross-linked gradient bicrystal phase polyurethane in the fields of intelligent drivers or intelligent brakes and the like to be more controllable and intelligent.
The cross-linked gradient two-crystal phase polyurethane provided by the present invention and the preparation method and application thereof are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
In each example, the source of the feed was as follows: poly (e-caprolactone) diol (PCL-2oh, mn =2000 and Mn =3000, polyformalization chemical), ω -pentadecanolide (PDL, annage), 1, 8-octanediol (annage), 1,5, 7-triazabicyclo (4.4.0) dec-5-ene (TBD, annage), dibutyltin dilaurate (DBTDL, annage), allyl isocyanate (alatin), DMF (national reagent), n-hexane (national reagent), chloroform (national reagent), n-heptane (national reagent), polyethylene glycol diacrylate (Mn =2000 and Mn =3000, alfaaesar corporation), trimethylolpropane tris (3-mercaptopropionate) (TMPMP, annage), photoinitiator 651 (annage), trichloroethane (national reagent).
In each embodiment, the power of the ultraviolet lamp is 250W, the wavelength of the light source is 315-450 nm, and the dominant wavelength is 365nm.
Example 1
The preparation process of the cross-linked gradient bicrystal phase polyurethane comprises the following steps:
(1) Poly (omega-pentadecanolide) diol synthesis: 102g of omega-pentadecanolide, 3.59g of 1, 8-octanediol and 3.41g of 1,5, 7-triazabicyclo (4.4.0) dec-5-ene (TBD) are placed in a three-neck flask, a condensing device is connected, and magnetic stirring is carried out for 48 hours at the temperature of 100 ℃; dissolving the obtained reaction solution in excessive chloroform, precipitating in n-hexane, filtering the precipitate, and drying to obtain poly (omega-pentadecanolide) glycol powder.
(2) Poly (omega-pentadecanolide) diallylcarboxamide and poly (epsilon-caprolactone) diallylcarboxamide synthesis: weighing 8.5g of the obtained poly (omega-pentadecanolide) dihydric alcohol into a three-neck flask, adding 10g of DMF solvent, 0.79mL of allyl isocyanate and 0.15g of dibutyltin dilaurate (DBTDL), introducing nitrogen, adding into a condensing device, and magnetically stirring at 85 ℃ for reacting for 5 hours; and precipitating the obtained reaction solution in n-heptane, washing and drying to obtain the poly (omega-pentadecanolide) diallyl formamide.
20g of poly (. Epsilon. -caprolactone) diol (Mn = 3000), 10g of DMF solvent, 1.63mL of allyl isocyanate and 0.3g of DBTDL were reacted under the same conditions as above for 5h to obtain poly (. Epsilon. -caprolactone) diallylcarboxamide.
(3) Synthesizing cross-linked gradient bicrystal phase polyurethane: dissolving 0.3g of poly (omega-pentadecanolide) diallyl formamide, 1.7g of poly (epsilon-caprolactone) diallyl formamide, 0.2016g of trimethylolpropane tris (3-mercaptopropionate) (TMPMP) and 0.04g of photoinitiator 651 in 4.67g of trichloroethane, pouring the obtained solution into an open culture dish, curing the open surface under an ultraviolet lamp (the distance between the surface of the solution and the ultraviolet lamp is 7 cm) for 5min, inverting the open culture dish, curing the other surface (the distance between the surface and the ultraviolet lamp is 5 cm) for 3min, and then placing the open culture dish in an oven at 50 ℃ to remove the solvent to obtain the crosslinking gradient bicrystal phase polyurethane.
The shape memory cycle curve was obtained under DMAQ800, with the specific temperature parameter selected as T p ＝95℃，T high ＝60℃，T low =0 ℃, thermomechanical programming strain 100% and 200%. The realization process is as follows: sample at T p Stretching to 100% (or 200%) strain at (95 deg.C) (10 min of incubation); then cooling the mixture to 0 ℃, wherein the cooling rate is 5 ℃/min, and keeping the temperature for 10min; then removing the stress on the sample, and keeping the temperature at 0 ℃ for 10min; the sample was then reheated to T high (60 ℃) for 10min without stress, and then cooled again to T low (0 ℃) (without stress), keeping the temperature for 10min, and increasing and reducing the temperature rate to 5 ℃/min; finally, at T high -T low The above heating and cooling cycle is repeated.
After the above test, note T high Strain of lower specimen to ε 1 ，T low Strain of lower sample to epsilon 2 Then define the material drive strain ε 1 -ε 2 The absolute value of (a) is not described in detail below. The cross-linked gradient twinned phase polyurethane prepared in example 1 exhibited a high temperature (T) at a programmed strain of 100% high (T) becomes smaller at =60 ℃ and larger at low temperature low =0 ℃), a drive strain value of 12.5%; and the driving strain shows a high temperature (T) when the programming strain is 200% high Larger at =60 ℃ and smaller at low temperature (T) low =0 ℃), and the drive strain value was 3.5%.
FIG. 1 is a graph of the two-way shape memory cycle test at 100% programmed strain for the cross-linked graded bi-crystalline phase polyurethane prepared in example 1. See its T in FIG. 1 high (60 ℃) strain below T low (0 ℃) indicates that the strain of the material is reduced at high temperature and low temperatureThe lower part of the polyurethane becomes larger, which accords with the two-way shape memory performance of common bicrystal phase polyurethane.
FIG. 2 is a graph of the two-way shape memory cycle at 200% programmed strain for the cross-linked gradient twin-phase polyurethane prepared in example 1. As can be seen from fig. 2, T high (60 ℃) strain higher than T low (0 ℃) indicates that the strain of the material increases at high temperature and decreases at low temperature. At this time, 200% of the programmed strain triggers different properties from the two-way shape memory of general two-phase polyurethane.
Example 2
The preparation process of the cross-linked gradient bicrystal phase polyurethane comprises the following steps:
(1) The poly (omega-pentadecanolide) diol synthesis was the same as in example 1.
(2) Poly (ω -pentadecanolide) diallylcarboxamide and poly (e-caprolactone) diallylcarboxamide synthesis: the synthesis of poly (omega-pentadecanolide) diallylcarboxamide was the same as in example 1.
15g of poly (. Epsilon. -caprolactone) diol (Mn = 2000), 10g of DMF solvent, 1.63mL of allyl isocyanate, and 0.2g of DBTDL were reacted under the same conditions as in example 1 for 5 hours to obtain poly (. Epsilon. -caprolactone) diallylcarboxamide.
(3) The cross-linked gradient bicrystal phase polyurethane synthesis was the same as example 1.
The shape memory cycle curve is obtained under DMA Q800, and the specific temperature parameter is selected as T p ＝95℃，T high ＝60℃，T low =0 ℃, the thermomechanical programming strain is divided into 100% and 200%. The temperature cycle was the same as in example 1. The cross-linked gradient twinned phase polyurethane prepared in example 2 was tested to exhibit a high temperature (T) driving strain at a programmed strain of 100% high Is smaller at =60 ℃) and larger at low temperature (T) low =0 ℃), value of 10%; the driving strain shows a high temperature (T) when the programming strain is 200% high Larger at =60 ℃ and smaller at low temperature (T) low =0 ℃), a value of 2%.
Example 3
The preparation process of the cross-linked gradient bicrystal phase polyurethane comprises the following steps:
(1) The poly (omega-pentadecanolide) diol synthesis was the same as in example 1.
(2) The synthesis of poly (omega-pentadecanolide) diallylcarboxamide was the same as in example 1.
(3) Synthesizing cross-linked gradient bicrystal phase polyurethane: dissolving 0.3g of poly (omega-pentadecanolide) diallyl formamide, 1.7g of polyethylene glycol diacrylate (Mn = 3000), 0.3g of TMPMP and 0.04g of photoinitiator 651 in 4.67g of trichloroethane, pouring the obtained solution into an open culture dish, curing the open surface under an ultraviolet lamp (the surface of the solution is 7cm away from the ultraviolet lamp) for 5min, then curing the other surface (the surface is 5cm away from the ultraviolet lamp) for 3min by inverting, and removing the solvent at 50 ℃ to obtain the crosslinking gradient bicrystal phase polyurethane.
The shape memory cycle curve is obtained under DMA Q800, and the specific temperature parameter is selected as T p ＝95℃，T high ＝60℃，T low =0 ℃, the thermomechanical programming strain is divided into 100% and 200%. The temperature cycle was the same as in example 1. The cross-linked gradient bicrystal phase polyurethane prepared in example 3 is tested to show high temperature (T) when the driving strain is 100% at the programming strain high (T) becomes smaller at =60 ℃ and larger at low temperature low =0 ℃), a value of 11%; the driving strain shows a high temperature (T) when the programming strain is 200% high Larger at =60 ℃ and smaller at low temperature (T) low =0 ℃), a value of 4%.
Example 4
The preparation process of the cross-linked gradient bicrystal phase polyurethane comprises the following steps:
(1) The poly (omega-pentadecanolide) diol synthesis was the same as in example 1.
(2) The synthesis of poly (omega-pentadecanolide) diallylcarboxamide was the same as in example 1.
(3) Synthesizing cross-linked gradient bicrystal phase polyurethane: dissolving 0.3g of poly (omega-pentadecanolide) diallyl formamide, 1.7g of polyethylene glycol diacrylate (Mn = 2000), 0.4g of TMPMP and 0.04g of photoinitiator 651 in 4.67g of trichloroethane, pouring the obtained solution into an open culture dish, curing the open surface under an ultraviolet lamp (the distance between the surface of the solution and the ultraviolet lamp is 7 cm) for 5min, then curing the other surface (the distance between the surface and the ultraviolet lamp is 5 cm) for 3min by inverting, and finally removing the solvent at 50 ℃ to obtain the crosslinking gradient bicrystal phase polyurethane.
Shape memory cycle curves were obtained under DMA Q800, with a specific temperature parameter selected as T p ＝95℃，T high ＝60℃，T low =0 ℃, the thermomechanical programming strain was divided into 100% and 200%, and the temperature cycling process was the same as in example 1. Through the above tests, the driving strain of the cross-linked gradient bi-crystalline phase polyurethane prepared in example 4 is expressed as high temperature (T) when the programming strain is 100% high Is smaller at =60 ℃) and larger at low temperature (T) low =0 ℃), a value of 9%; the driving strain shows a high temperature (T) when the programming strain is 200% high Larger at =60 ℃ and smaller at low temperature (T) low =0 ℃), a value of 3.4%.
Comparative example 1
By controlling the curing process parameters, the bicrystal phase polyurethane without crosslinking gradient is synthesized, and the bidirectional shape memory performance of the bicrystal phase polyurethane is tested, which comprises the following steps:
(1) The synthesis of poly (omega-pentadecanolide) diol was the same as in example 1.
(2) The synthesis of poly (omega-pentadecanolide) diallylcarboxamide and poly (epsilon-caprolactone) diallylcarboxamide was the same as in example 1.
(3) Synthesizing non-crosslinking gradient bicrystal phase polyurethane: 0.3g of poly (omega-pentadecanolide) diallylformamide, 1.7g of poly (epsilon-caprolactone) diallylformamide, 0.2016g of TMPMP and 0.04g of photoinitiator 651 are dissolved in 4.67g of trichloroethane, and the solution obtained is poured into an open culture dish, and the open face and the back face are alternately cured for 1min and 4 times to obtain the non-crosslinked gradient polyurethane.
The shape memory cycle curve is obtained under DMA Q800, and the specific temperature parameter is selected as T p ＝95℃，T high ＝60℃，T low =0 ℃, the thermomechanical programming strain is divided into 100% and 200%. The temperature cycle was the same as in example 1. Through the above tests, the non-crosslinking gradient polyurethane prepared in comparative example 1 has a driving strain showing a high temperature (T) at a programmed strain of 100% high (T) becomes smaller at =60 ℃ and larger at low temperature low =0 ℃), a value of 9%; the driving strain of the strain is in the weaveWhen the strain of the process is 200%, the high temperature (T) is still expressed high (T) becomes smaller at =60 ℃ and larger at low temperature low =0 ℃), a value of 20%.
Comparative example 1 a polyurethane having no crosslinking gradient was obtained by curing the open face and the back face alternately for 1min so that the crosslinking gradient due to the penetration depth of ultraviolet rays was eliminated as much as possible. FIG. 3 is a graph of the two-way shape memory cycle at 200% programmed strain for the non-crosslinked gradient polyurethane prepared in comparative example 1, T high (60 ℃) strain below T low (0 ℃) is higher than the temperature, which shows that the driving strain of the material is reduced at high temperature and increased at low temperature, and the driving strain and the temperature change trend of the material under 200% programming strain is the same as the driving strain and the temperature change trend of the material under 100% programming strain. The test results according to comparative example 1 show that the introduction of a crosslinking gradient into a bi-crystalline polyurethane system is critical for achieving a reversal of the trend of the driving strain with temperature at 200%.
It can be seen from the above embodiments that the present invention realizes the reversible reversal of the trend of the driving strain controlled by the tensile programming strain along with the temperature, which is not possessed by the traditional semi-crystalline two-way shape memory material: the drive strain at low programming strain (100%) becomes smaller hot and larger cold; while at high programming strains (200%) the drive strain becomes larger hot and smaller cold. The cross-linked gradient bicrystal phase polyurethane prepared by the invention has a unique two-way shape memory effect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of cross-linked gradient bicrystal phase polyurethane comprises the following steps:
mixing poly (omega-pentadecanolide) diol, allyl isocyanate, a first catalyst and a first organic solvent to perform a first addition reaction to obtain poly (omega-pentadecanolide) diallyl formamide;
mixing poly (epsilon-caprolactone) dihydric alcohol, allyl isocyanate, a second catalyst and a second organic solvent to perform a second addition reaction to obtain poly (epsilon-caprolactone) diallyl formamide;
and mixing the poly (omega-pentadecanolide) diallyl formamide, a third organic solvent, a mercapto-group crosslinking agent and a photoinitiator with poly (epsilon-caprolactone) diallyl formamide or polyethylene glycol diacrylate, carrying out first ultraviolet irradiation curing on the upper surface of the obtained mixed solution, and then carrying out second ultraviolet irradiation curing on the lower surface of the mixed solution to obtain the crosslinking gradient bicrystal phase polyurethane.
2. The method according to claim 1, wherein the method for producing the poly (ω -pentadecanolide) diol comprises:
mixing omega-pentadecanolide, 1, 8-octanediol and a third catalyst to perform ring-opening polymerization reaction to obtain poly (omega-pentadecanolide) diol.
3. The method of claim 2, wherein the third catalyst is 1,5, 7-triazabicyclo (4.4.0) dec-5-ene; the mass of the third catalyst is 1-3% of the sum of the mass of the omega-pentadecanolide, the mass of the 1, 8-octanediol and the mass of the third catalyst, and the mass of the 1, 8-octanediol is 2-3.5% of the sum of the mass of the omega-pentadecanolide, the mass of the 1, 8-octanediol and the mass of the third catalyst; the temperature of the ring-opening polymerization reaction is 90-120 ℃, and the time is 48-72 h.
4. The method according to claim 1, wherein the first catalyst and the second catalyst are dibutyltin dilaurate; the temperature of the first addition reaction and the second addition reaction is independently 80-90 ℃, and the time is independently 3.5-6 h; the first addition reaction and the second addition reaction are both carried out under a protective atmosphere.
5. The method according to claim 1 or 4, wherein in the first addition reaction, the molar ratio of poly (ω -pentadecanolide) diol to allyl isocyanate is 1; the mass of the first catalyst is 0.5-2% of that of the poly (omega-pentadecanolide) diol.
6. The method according to claim 1 or 4, wherein in the second addition reaction, the molar ratio of poly (epsilon-caprolactone) diol to allyl isocyanate is 1; the mass of the second catalyst is 0.5-2% of that of the poly (epsilon-caprolactone) diol.
7. The method of manufacturing of claim 1, wherein said mercapto cross-linking agent is trimethylolpropane tris (3-mercaptopropionate); the mass of the poly (omega-pentadecanolide) diallyl formamide is 5-20% of the sum of the mass of the poly (omega-pentadecanolide) diallyl formamide and the mass of the poly (epsilon-caprolactone) diallyl formamide or the sum of the mass of the poly (omega-pentadecanolide) diallyl formamide and the mass of the polyethylene glycol diacrylate; the ratio of the total molar amount of double bonds in the poly (omega-pentadecanolide) diallyl formamide and the poly (epsilon-caprolactone) diallyl formamide or the polyethylene glycol diacrylate to the molar amount of sulfydryl in the sulfydryl crosslinking agent is 3.
8. The method according to claim 1, wherein the power of the ultraviolet light source used in the first ultraviolet radiation curing and the second ultraviolet radiation curing is 250W, the wavelength of the light source is 315 to 450nm, and the distance between the ultraviolet light source and the upper surface or the lower surface of the mixed solution is independently 5 to 10cm; the first ultraviolet irradiation curing time is 5-10 min, the second ultraviolet irradiation curing time is 2-8 min, and the first ultraviolet irradiation curing time is longer than or equal to the second ultraviolet irradiation curing time.
9. The cross-linked gradient bi-crystalline phase polyurethane prepared by the preparation method of any one of claims 1 to 8.
10. Use of the cross-linked gradient twin phase polyurethane according to claim 9 in smart actuators or smart brakes.
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| CN101346407A (en) * | 2005-12-22 | 2009-01-14 | 记忆科学有限公司 | Macro-diacrylates and macro-polyacrylates |
| US20130277890A1 (en) * | 2010-11-04 | 2013-10-24 | The Regents Of The University Of Colorado, A Body Corporate | Dual-Cure Polymer Systems |
| US20170349707A1 (en) * | 2014-12-10 | 2017-12-07 | Joanneum Research Forschungsgesellschaft Mbh | Poly- or prepolymer composition, or embossing lacquer comprising such a composition and use thereof |
| US20180009932A1 (en) * | 2015-02-03 | 2018-01-11 | Lawrence Livermore National Security, Llc | Processable, tunable thio-ene crosslinked polyurethane shape memory polymers |
| CN110527036A (en) * | 2019-09-12 | 2019-12-03 | 临沂大学 | High molecular material and preparation method thereof with water-responsive bidirectional reversible shape memory function |
| CN113105607A (en) * | 2021-04-09 | 2021-07-13 | 青岛科技大学 | Self-repairing polyurethane cross-linked network containing UPy side chain, preparation method and application |
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