Fabrication and application of shape memory polymer possessing transesterification induced permanent reshaping property

Abstract

The present invention discloses the fabrication and application of a shape memory polymer possessing transesterification-induced permanent reshaping. The ester-containing crosslinked polymer is obtained by crosslinking ester bearing polymer precursors or by reaction of monomers which yield ester bonds. The transition temperature falls between 20-150 C. The reshaping temperature is tuned by catalyst amount and should be 20 C. above the transition temperature. The breakthrough of the present invention lies in integrating shape memory effect and plastic deformation into the same polymer and triggering the respective function at different occasions. The permanent shape of as synthesized polymer could be modified arbitrarily and cumulatively. Therefore, the hierarchical structure which could not otherwise be obtained due to the limit of mold fabrication process should expand the practical application of SMPs.

Claims

1. An application method of a shape memory polymer possessing transesterification-induced permanent reshaping property, the method comprising the steps of: (1) when the temperature reaches reshaping temperature, under the impact of an external force, the polymer with a certain original shape is changed to an arbitrary desired new shape (shape I); (2) the temperature and external force remain stable to allow the transesterification reactions in the polymer system until dynamic equilibrium is reached; (3) the new shape is fixed under cooling and now defined as the new original shape (shape II); (4) the processed polymer is further altered to a temporary shape (shape III) after being heated above the phase transformation temperature under an external force; (5) the temporary shape of step (4) shall be fixed after cooling below the phase transformation temperature; (6) the polymer obtained from step (5) is reheated to above its the phase transformation temperature so that the polymer will recover to the fixed shape (shape II) obtained in step (3) from the temporary shape of step (5); wherein the shape memory polymers are crosslinked polymers with ester bonds and with a transesterification catalyst present; wherein the catalyst is selected from the group consisting of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, benzyldimethylamide, and metal salts of tin, zinc, magnesium, cobalt, calcium, titanium, or zirconium; wherein the crosslinked polymers with ester bonds are obtained by crosslinking reaction of crosslinking polymer precursors containing ester bonds or obtained by reaction of two or more crosslinking polymer precursors without ester bonds to form ester bonds; phase transition temperature of the polymers is 20-150 C.; reshaping temperature is at least 20 C. higher than the phase transition temperature; wherein the ester-containing crosslinked polymer is obtained by reaction of epoxy monomers and organic polyacids or anhydrides.

2. The method of claim 1, wherein the phase transition temperature of the polymers is 40-70 C.; and the reshaping temperature is 100-140 C.

3. The method of claim 1, wherein the phase transformation temperature is glass transition or melting temperature of the polymers.

4. An application method of a shape memory polymer possessing transesterification-induced permanent reshaping property, the method comprising the steps of: (1) when the temperature reaches reshaping temperature, under the impact of an external force, the polymer with a certain original shape is changed to an arbitrary desired new shape (shape I); (2) the temperature and external force remain stable to allow the transesterification reactions in the polymer system until dynamic equilibrium is reached; (3) the new shape is fixed under cooling and now defined as the new original shape (shape II; (4) the processed polymer is further altered to a temporary shape (shape III) after being heated above the phase transformation temperature under an external force; (5) the temporary shape of step (4) shall be fixed after cooling below the phase transformation temperature; (6) the polymer obtained from step (5) is reheated to above its the phase transformation temperature so that the polymer will recover to the fixed shape (shape II) obtained in step (3) from the temporary shape of step (5); wherein the shape memory polymers are crosslinked polymers with ester bonds and with a transesterification catalyst present; wherein the catalyst is selected from the group consisting of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, benzyldimethylamide, and metal salts of tin, zinc, magnesium, cobalt, calcium, titanium, or zirconium; wherein the crosslinked polymers with ester bonds are obtained by crosslinking reaction of crosslinking polymer precursors containing ester bonds or obtained by reaction of two or more crosslinking polymer precursors without ester bonds to form ester bonds; phase transition temperature of the polymers is 20-150 C.; reshaping temperature is at least 20 C. higher than the phase transition temperature; wherein the ester-containing crosslinked polymer is obtained by crosslinking a saturated polyester with vinyl end groups.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: DMA curve of thermo-adaptable SMP with synthesized as embodiment 1.

(2) FIG. 2: DMA curve of thermo-adaptable SMP with synthesized as embodiment 2.

(3) FIG. 3: DMA curve of thermo-adaptable SMP with synthesized as embodiment 3.

(4) FIG. 4: DMA curve of thermo-adaptable SMP with synthesized as embodiment 4.

(5) FIG. 5: DMA curve of thermo-adaptable SMP with synthesized as embodiment 5.

(6) FIG. 6: DMA curve of thermo-adaptable SMP with synthesized as embodiment 6.

(7) FIG. 7 shows the detailed application process of embodiment 1.

DETAILED EMBODIMENTS OF THE PRESENT INVENTION

(8) A further illustration of the invention is made with examples. The invention, however, demands protection of embodiment more than these examples.

Example 1

(9) Materials:

(10) a) Polycarprolactone diacrylate (PCLDA): Mw=10,000, from Sigma-Aldrich, molecular structure as follows:

(11) ##STR00001##

(12) b) Pentaerythritol tetrakis(3-mercaptopropionate) (Tetrathiol): from Sigma-Aldrich, molecular structure as follows:

(13) ##STR00002##

(14) c) 1-Hydroxylcyclohexyl phenyl ketone (UV-184): from TCI Company

(15) d) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(16) e) N,N-Dimethylformamide (DMF): from Aladdin (Shanghai) Co., Ltd.

(17) Preparation Methods:

(18) 1 mmol of PCLDA and 0.5 mmol of Tetrathiol were added into 10 ml of DMF (wherein the mass ratio of PCLDA and Tetathiol is that the molar ration of double bond and mercapto (sulfanyl) group=1:1, molar ratio) and the temperature was elevated to 80 C. to obtain a thoroughly uniform solution. Then UV-184 (0.5% w.t.) and TBD (2% w.t.) were added in and the solution was further stirred. The solution was poured into a sealed glass mold and the mold was exposed under 365 nm UV for 5 min for curing. The obtained film was taken out and dried under vacuum for 24 hours at 100 C.

Example 2

(19) Materials:

(20) a) Polycarprolactone diacrylate (PCLDA): Mw=10,000, from Sigma-Aldrich

(21) b) Pentaerythritol tetrakis(3-mercaptopropionate) (Tetrathiol): from Sigma-Aldrich

(22) c) Triethylamine (TEA): from TCI Company

(23) d) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(24) e) N,N-Dimethylformamide (DFM): from Aladin (Shanghai) Co., Ltd.

(25) Preparation Methods:

(26) 1 mmol of PCLDA and 0.5 of mmol Tetrathiol were added into 20 ml of DMF (wherein the mass ratio of PCLDA and Tetathiol is that the molar ration of double bond and mercapto (sulfanyl) group=1:1, molar ratio) and the temperature was elevated to 80 C. obtain a uniform solution. Then TEA (0.5% w.t.) and TBD (2% w.t.) were added in and the solution was further stirred. The solution was poured into a sealed glass mold and the mold was placed at 60 C. oven for 4 hours for curing. The obtained film was taken out and dried under vacuum for 24 hours at 100 C.

Example 3

(27) Materials:

(28) a) Unsaturated polyester oligomer: phthalic acid type, 15% w.t. maleic anhydride

(29) b) Styrene: from Aladdin (Shanghai) Co., Ltd.

(30) c) 1-Hydroxylcyclohexyl phenyl ketone (UV-184): from TCI Company

(31) d) Cobaltous naphthenate: from Aladin (Shanghai)

(32) e) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(33) Preparation Methods:

(34) 6.5 g of unsaturated polyester oligomer (phthalic acid type, 15% w.t. maleic anhydride), 3.5 g of styrene, 0.1 g of UV-184, 0.05 g of cobaltous naphthenate and 0.2 g of TBD were mixed together and the uniform solution was poured into the aluminum plate then the plate was placed into the oven at 50 C. for 2 hours, followed by 80 C. for 5 hours to obtain the thermoset unsaturated polyester.

Example 4

(35) Materials:

(36) a) Bisphenol A diglycidyl ether (DGEBA): Mw=340, from Aladdin (Shanghai) Co., Ltd.

(37) b) Glutaric anhydride: Mw=114, from Aladdin (Shanghai) Co., Ltd.

(38) c) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(39) d) N,N-Dimethylformamide (DFM): from Aladin (Shanghai) Co., Ltd.

(40) Preparation Methods:

(41) 1 mmol of DGEBA and 1 mmol of glutaric anhydride were added into 20 ml of DMF and the temperature was elevated to 100 C. to get the thoroughly uniform solution. Then TBD (2%) was added in and the solution was further stirred. The solution was poured into a PTFE mold and the mold was placed at 130 C. oven for 4 hours for curing.

Example 5

(42) Materials:

(43) a) Polycarprolactone diol (PCL diol): Mw=10,000, from Sigma-Aldrich, molecular structure as follows:

(44) ##STR00003##

(45) b) Hexamethylene diisocyanate (HDI): from Sigma-Aldrich, CAS: 28182-81-2, molecular structure as follows:

(46) ##STR00004##

(47) c) Dibutyltin dilaurate (DBTDL): from TCI Company

(48) d) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(49) e) N,N-Dimethylformamide (DFM): from Aladdin (Shanghai) Co., Ltd.

(50) Preparation Methods:

(51) 0.3 mmol of PCL and 0.2 mmol of HDI were added into 10 ml of DMF (wherein the mass ratio of PCL and HDI is that the molar ration of hydroxy and isocynate group: hydroxy:isocynate=1:1, molar ratio) and elevate the temperature to 80 C. to get the thoroughly uniform solution. Then DBTDL (0.5% w.t.) and TBD (2% w.t.) were added in and the solution was further stirred. The solution was poured into a mold and the mold was placed at 90 C. for 12 hours for curing. The obtained film was taken out and dried under vacuum for 24 hours at 100 C.

Example 6

(52) Materials:

(53) a) Polycarprolactone diol (PCL diol): Mw=10,000, from Sigma-Aldrich, molecular structure as follows:

(54) b) triphenylmethane-4,4,4-triisocyanate: from Sigma-Aldrich

(55) c) Dibutyltin dilaurate (DBTDL): from TCI Company

(56) d) 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD): from TCI Company

(57) e) N,N-Dimethylformamide (DFM): from Aladdin (Shanghai) Co., Ltd.

(58) Preparation Methods:

(59) 0.3 mmol of PCL and 0.2 mmol of triphenylmethane-4,4,4-triisocyanate were added into 10 ml DMF (wherein the mass ratio of PCL and triphenylmethane-4,4,4-triisocyanate is that the molar ration of hydroxy and isocynate group: hydroxy:isocynate=1:1, molar ratio) and the temperature was elevated to 80 C. to get the thoroughly uniform solution. Then DBTDL (0.5% w.t.) and TBD (2%) were added in and the solution was further stirred. The solution was poured into a mold and the mold was placed at 90 C. for 12 hours for curing. The obtained film was taken out and dried under vacuum for 24 hours at 100 C.

(60) DSC (Differential scanning calorimetry) tests showed the transition temperature of synthesized samples of Examples 1-6 falls between 50-100 C. DMA (Dynamic mechanical analysis) stress relaxation tests indicated the higher the temperature, the faster complete plastic deformation was achieved. Several minutes or hours might be needed to complete relaxation at 130 C.

(61) The sample for DMA test was cut from the film by laser engraver machine. Followed practice is characterization procedure for plasticity and shape memory performance for Example 1 to obtain FIG. 1.

(62) Shape memory effect: Stretch the sample at 70 C. until the stress reached 120 MPa and then cooled the sample to 0 C. and removed the internal force. This fixed the temporary shape. The sample in this temporary shape should recover to the original shape upon 70 C.

(63) Reshaping: The sample was stretched to a constant length isothermally and the stress was allowed to relax completely as enabled by transesterification.

(64) FIG. 2 shows the performance of reshaping and shape memory effect of Example 2. FIG. 3 shows the performance of reshaping and shape memory effect of Example 3. FIG. 4 shows the performance of reshaping and shape memory effect of Example 4. FIG. 5 shows the performance of reshaping and shape memory effect of Example 5. FIG. 6 shows the performance of reshaping and shape memory effect of Example 6.

(65) An application process of the invention is demonstrated as follows:

(66) As FIG. 7 shows, the sample from Example 1 was cut into a specific shape, the sample was heated to 130 C. and then the sample was folded into a crane. A permanent crane shape was obtained after certain time. The crane was heated above the phase transition temperature to deform the crane into a sheet of paper (temporary shape I) or arbitrary (temporary shape II) and the sample was cooled to fix the temporary shape. The material of arbitrary temporary shape shall recover to the crane above the transition temperature.

Example 7-9

(67) The polycaprolactone idol in Example 5 was replaced with polyethyleneglycol-propyleneglycol adipate, polydiethyleneglycol adipate, poly-1,4-butyleneglycol adipate and the isocyanate-hydroxyl crosslinking chemistry was applied. The test showed the as-prepared sample exhibits reshaping and shape memory effect and a similar transition temperature of sample from Example 5. While the resolution of the permanent shape obtained from the reshaping process was less satisfied compared with Example 5, it shall be as well acceptable for occasions that requires no such accuracy.

Example 10-11

(68) The pentaerythritol tetrakis(3-mercaptopropionate) was replaced with pentaerythritol tetrakis(2-mercaptoacetate) in Examples 1 and 2, a similar result as Examples 1 and 2 was obtained.

Example 12

(69) The glutaric anhydride was replaced with decanedioicacid, a similar result as Example 4 was obtained.