Influence of Chain Architectures on Crystallization Behaviors of PLLA Block in PEG/PLLA Block Copolymers
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摘要
The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA(4PEG-b-PLLA) were synthesized by the ring-opening polymerization of Llactide in the presence of poly(ethylene glycol) methyl ether(MPEG) and 4-arm poly(ethylene glycol)(4PEG). 4-Arm PLLA-b-MPEG(4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index(ˉn) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG-b-PLLA > 4PLLA-b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.
The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA(4PEG-b-PLLA) were synthesized by the ring-opening polymerization of Llactide in the presence of poly(ethylene glycol) methyl ether(MPEG) and 4-arm poly(ethylene glycol)(4PEG). 4-Arm PLLA-b-MPEG(4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index(ˉn) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG-b-PLLA > 4PLLA-b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.
The effect of the architecture of poly(ethylene glycol)/poly(L-lactide)(PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry(DSC) and wide angle X-ray diffraction(WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA(4PEG-b-PLLA) were synthesized by the ring-opening polymerization of Llactide in the presence of poly(ethylene glycol) methyl ether(MPEG) and 4-arm poly(ethylene glycol)(4PEG). 4-Arm PLLA-b-MPEG(4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index(ˉn) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG-b-PLLA > 4PLLA-b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.
引文
1Pang, X.; Zhuang, X.; Tang, Z.; Chen, X. Polylactic acid (PLA): Research, development and industrialization. Biotechnol. J. 2010, 5,1125-1136.
2Rasal, R. M.; Janorkar, A. V.; Hirt, D. E. Poly(lactic acid) modifications. Prog. Polym. Sci. 2010, 35, 338-356.
3Nampoothiri, K. M.; Nair, N. R.; John, R. P. An overview of the recent developments in polylactide (PLA) research. Bioresour. Technol. 2010, 101, 8493-8501.
4Shi, X. D.; Sun, P. J.; Gan Z. H. Preparation of porous polylactide microspheres and their application in tissue engineering.Chinese J. Polym. Sci. 2018, 36, 712-719.
5Sun, Y.; He, C. Biodegradable “core-shell” rubber nano-particles and their toughening of poly(lactides). Macromolecules 2013, 46, 9625-9633.
6Huang, S.; Sun, H.; Sun, J.; Li, G.; Chen, X. Biodegradable tough blends of poly(L-lactide) and poly(castor oil)-poly(L-lactide) copolymer. Mater. Lett. 2014, 133, 87-90.
7Liu, Y.; Sun, J.; Bian, X.; Feng, L.; Xiang, S.; Sun, B.; Chen,Z.; Li, G.; Chen, X. Melt stereocomplexation from poly(L-lactic acid) and poly(D-lactic acid) with different optical purity.Polym. Degrad. Stab. 2013, 98, 844-852.
8Sun, C. B.; Mao, H. D.; Chen, F.; Fu, Q. Preparation of polylactide composite with excellent flame retardance and improved mechanical properties. Chinese J. Polym. Sci. 2018, 36,1385-1393.
9Liu, Y.; Shao, J.; Sun, J.; Bian, X.; Chen, Z.; Li, G.; Chen, X.Toughening effect of poly(D-lactide)-b-poly(butylene succinate)-b-poly(D-lactide) copolymers on poly(L-lactic acid) by solution casting method. Mater. Lett. 2015, 155, 94-96.
10Ba, C.; Yang, J.; Hao, Q.; Liu, X.; Cao, A. Syntheses and physical characterization of new aliphatic triblock poly(L-lactide-bbutylene succinate-b-L-lactide)s bearing soft and hard biodegradable building blocks. Biomacromolecules 2003, 4,1827-1834.
11Peponi, L. Marcos-Fernández, A. Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers. Polymer 2012, 53, 4561-4568.
12Casas, M. T.; Puiggalí, J.; Raquez, J. M.; Dubois, P.; Córdova,M. E.; Müller, A. J. Single crystals morphology of biodegradable double crystalline PLLA-b-PCL diblock copolymers. Polymer 2011, 52, 5166-5177.
13Cerrai, P.; Tricoli, M.; Lelli, L.; Guerra, G. D.; Delguerra, R.S.; Cascone, M. G.; Giusti, P. Block-copolymers of L-lactide and poly(ethylene glycol) for biomedical applications. J. Mater.Sci-Mater. M. 1994, 5, 308-313.
14Kim, K. S.; Chung, S.; Chin, I. J.; Kim, M. N.; Yoon, J. S.Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)-poly(L-lactide) block copolymers. J. Appl. Polym. Sci. 1999, 72, 341-348.
15Liu, Y.; Shao, J.; Sun, J.; Bian, X.; Feng, L.; Xiang, S.; Sun, B.;Chen, Z.; Li, G.; Chen, X. Improved mechanical and thermal properties of PLLA by solvent blending with PDLA-b-PEG-b-PDLA. Polym. Degrad. Stab. 2014, 101, 10-17.
16Ren, K.; Cheng, Y.; He, C.; Xiao, C.; Li, G.; Chen, X. The effect of alkyl side groups on the secondary structure and crystallization of poly(ethylene glycol)-block-polypeptide copolymers. Polymer 2013, 54, 2466-2472.
17Shin, D.; Shin, K.; Aamer, K. A.; Tew, G. N.; Russell, T. P.;Lee, J. H.; Jho, J. Y. A Morphological study of a semicrystalline poly(L-lactic acid-b-ethylene oxide-b-L-lactic acid) triblock copolymer. Macromolecules 2005, 38, 104-109.
18Yang, J.; Liang, Y.; Luo, J.; Zhao, C.; Han, C. C. Multilength scale studies of the confined crystallization in poly(L-lactide)-block-poly(ethylene glycol) copolymer. Macromolecules 2012,45, 4254-4261.
19Sun, J.; Hong, Z.; Yang, L.; Tang, Z.; Chen, X.; Jing, X. Study on crystalline morphology of poly(L-lactide)-poly(ethylene glycol) diblock copolymer. Polymer 2004, 45, 5969-5977.
20Sun, J. R.; Chen, X. S.; He, C. L.; Jing, X. B. Morphology and structure of single crystals of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers. Macromolecules 2006, 39,3717-3719.
21Zhang, J. M.; Duan, Y. X.; Domb, A. J.; Ozaki, Y. PLLA mesophase and its phase transition behavior in the PLLA-PEG-PLLA copolymer as revealed by infrared spectroscopy. Macromolecules 2010, 43, 4240-4246.
22Zhou, D.; Shao, J.; Li, G.; Sun, J.; Bian, X.; Chen, X. Crystallization behavior of PEG/PLLA block copolymers: Effect of the different architectures and molecular weights. Polymer 2015, 62, 70-76.
23Yang, J.; Zhao, T.; Cui, J.; Liu, L.; Zhou, Y.; Li, G.; Zhou, E.;Chen, X. Nonisothermal crystallization behavior of the poly(ethylene glycol) block in poly(L-lactide)-poly(ethylene glycol) diblock copolymers: Effect of the poly(L-lactide) block length. J. Polym. Sci., Part B: Polym. Phys. 2006, 44,3215-3226.
24Zhou, D.; Sun, J.; Shao, J.; Bian, X.; Huang, S.; Li, G.; Chen,X. Unusual crystallization and melting behavior induced by microphase separation in MPEG-b-PLLA diblock copolymer.Polymer 2015, 80, 123-129.
25Zhao, W.; Li, C. Y.; Wu, C. J.; Liu, X. L.; Mou, Z. H.; Yao, C.G.; Cui, D. M. Synthesis of ultraviolet absorption polylactide via immortal polymerization of rac-lactide initiated by a salanyttrium catalyst. Chinese J. Polym. Sci. 2018, 36, 202-206.
26Yao, F.; Bai, Y.; Zhou, Y.; Liu, C.; Wang, H.; Yao, K. Synthesis and characterization of multiblock copolymers based on Llactic acid, citric acid, and poly(ethylene glycol). J. Polym. Sci.,Part A: Polym. Chem. 2003, 41, 2073-2081.
27Feng, L. D.; Sun, B.; Bian, X. C.; Chen, Z. M.; Chen, X. S. Determination of D-lactate content in poly(lactic acid) using polarimetry. Polym. Test. 2010, 29, 771-776.
28Tsuji, H.; Matsumura, N.; Arakawa, Y. Stereocomplex crystallization and homocrystallization of star-shaped four-armed stereo diblock poly(lactide)s with different L-lactyl unit contents:Isothermal crystallization from the melt. J. Phys. Chem. B 2016, 120, 1183-1193.
29Pan, P.; Kai, W.; Zhu, B.; Dong, T.; Inoue, Y. Polymorphous crystallization and multiple melting behavior of poly(L-lactide):Molecular weight dependence. Macromolecules 2007, 40,6898-6905.
30Pan, P.; Zhu, B.; Kai, W.; Dong, T.; Inoue, Y. Polymorphic transition in disordered poly(L-lactide) crystals induced by annealing at elevated temperatures. Macromolecules 2008, 41,4296-4304.
31Shao, J.; Sun, J.; Bian, X.; Zhou, Y.; Li, G.; Chen, X. The formation and transition behaviors of the mesophase in poly(D-lactide)/poly(L-lactide) blends with low molecular weights.CrystEngComm 2013, 15, 6469-6476.
32Shao, J.; Xiang, S.; Bian, X.; Sun, J.; Li, G.; Chen, X. Remarkable melting behavior of PLA stereocomplex in linear PLLA/PDLA blends. Ind. Eng. Chem. Res. 2015, 54,2246-2253.
33Jeziorny, A. Parameters characterizing the kinetics of the non-isothermal crystallization of poly(ethylene terephthalate) determined by DSC. Polymer 1978, 19, 1142-1144.
34Liu, T.; Mo, Z.; Zhang, H. Nonisothermal crystallization behavior of a novel poly(aryl ether ketone): PEDEKmK. J. Appl.Polym. Sci. 1998, 67, 815-821.
35Vyazovkin, S.; Sbirrazzuoli, N. Isoconversional kinetic analysis of thermally stimulated processes in polymers. Macromol.Rapid Commun. 2006, 27, 1515-1532.
36Vyazovkin, S.; Dollimore, D. Linear and nonlinear procedures in isoconversional computations of the activation energy of nonisothermal reactions in solids. J. Chem. Inf. Model. 1996,36, 42-45.
2Rasal, R. M.; Janorkar, A. V.; Hirt, D. E. Poly(lactic acid) modifications. Prog. Polym. Sci. 2010, 35, 338-356.
3Nampoothiri, K. M.; Nair, N. R.; John, R. P. An overview of the recent developments in polylactide (PLA) research. Bioresour. Technol. 2010, 101, 8493-8501.
4Shi, X. D.; Sun, P. J.; Gan Z. H. Preparation of porous polylactide microspheres and their application in tissue engineering.Chinese J. Polym. Sci. 2018, 36, 712-719.
5Sun, Y.; He, C. Biodegradable “core-shell” rubber nano-particles and their toughening of poly(lactides). Macromolecules 2013, 46, 9625-9633.
6Huang, S.; Sun, H.; Sun, J.; Li, G.; Chen, X. Biodegradable tough blends of poly(L-lactide) and poly(castor oil)-poly(L-lactide) copolymer. Mater. Lett. 2014, 133, 87-90.
7Liu, Y.; Sun, J.; Bian, X.; Feng, L.; Xiang, S.; Sun, B.; Chen,Z.; Li, G.; Chen, X. Melt stereocomplexation from poly(L-lactic acid) and poly(D-lactic acid) with different optical purity.Polym. Degrad. Stab. 2013, 98, 844-852.
8Sun, C. B.; Mao, H. D.; Chen, F.; Fu, Q. Preparation of polylactide composite with excellent flame retardance and improved mechanical properties. Chinese J. Polym. Sci. 2018, 36,1385-1393.
9Liu, Y.; Shao, J.; Sun, J.; Bian, X.; Chen, Z.; Li, G.; Chen, X.Toughening effect of poly(D-lactide)-b-poly(butylene succinate)-b-poly(D-lactide) copolymers on poly(L-lactic acid) by solution casting method. Mater. Lett. 2015, 155, 94-96.
10Ba, C.; Yang, J.; Hao, Q.; Liu, X.; Cao, A. Syntheses and physical characterization of new aliphatic triblock poly(L-lactide-bbutylene succinate-b-L-lactide)s bearing soft and hard biodegradable building blocks. Biomacromolecules 2003, 4,1827-1834.
11Peponi, L. Marcos-Fernández, A. Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers. Polymer 2012, 53, 4561-4568.
12Casas, M. T.; Puiggalí, J.; Raquez, J. M.; Dubois, P.; Córdova,M. E.; Müller, A. J. Single crystals morphology of biodegradable double crystalline PLLA-b-PCL diblock copolymers. Polymer 2011, 52, 5166-5177.
13Cerrai, P.; Tricoli, M.; Lelli, L.; Guerra, G. D.; Delguerra, R.S.; Cascone, M. G.; Giusti, P. Block-copolymers of L-lactide and poly(ethylene glycol) for biomedical applications. J. Mater.Sci-Mater. M. 1994, 5, 308-313.
14Kim, K. S.; Chung, S.; Chin, I. J.; Kim, M. N.; Yoon, J. S.Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)-poly(L-lactide) block copolymers. J. Appl. Polym. Sci. 1999, 72, 341-348.
15Liu, Y.; Shao, J.; Sun, J.; Bian, X.; Feng, L.; Xiang, S.; Sun, B.;Chen, Z.; Li, G.; Chen, X. Improved mechanical and thermal properties of PLLA by solvent blending with PDLA-b-PEG-b-PDLA. Polym. Degrad. Stab. 2014, 101, 10-17.
16Ren, K.; Cheng, Y.; He, C.; Xiao, C.; Li, G.; Chen, X. The effect of alkyl side groups on the secondary structure and crystallization of poly(ethylene glycol)-block-polypeptide copolymers. Polymer 2013, 54, 2466-2472.
17Shin, D.; Shin, K.; Aamer, K. A.; Tew, G. N.; Russell, T. P.;Lee, J. H.; Jho, J. Y. A Morphological study of a semicrystalline poly(L-lactic acid-b-ethylene oxide-b-L-lactic acid) triblock copolymer. Macromolecules 2005, 38, 104-109.
18Yang, J.; Liang, Y.; Luo, J.; Zhao, C.; Han, C. C. Multilength scale studies of the confined crystallization in poly(L-lactide)-block-poly(ethylene glycol) copolymer. Macromolecules 2012,45, 4254-4261.
19Sun, J.; Hong, Z.; Yang, L.; Tang, Z.; Chen, X.; Jing, X. Study on crystalline morphology of poly(L-lactide)-poly(ethylene glycol) diblock copolymer. Polymer 2004, 45, 5969-5977.
20Sun, J. R.; Chen, X. S.; He, C. L.; Jing, X. B. Morphology and structure of single crystals of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers. Macromolecules 2006, 39,3717-3719.
21Zhang, J. M.; Duan, Y. X.; Domb, A. J.; Ozaki, Y. PLLA mesophase and its phase transition behavior in the PLLA-PEG-PLLA copolymer as revealed by infrared spectroscopy. Macromolecules 2010, 43, 4240-4246.
22Zhou, D.; Shao, J.; Li, G.; Sun, J.; Bian, X.; Chen, X. Crystallization behavior of PEG/PLLA block copolymers: Effect of the different architectures and molecular weights. Polymer 2015, 62, 70-76.
23Yang, J.; Zhao, T.; Cui, J.; Liu, L.; Zhou, Y.; Li, G.; Zhou, E.;Chen, X. Nonisothermal crystallization behavior of the poly(ethylene glycol) block in poly(L-lactide)-poly(ethylene glycol) diblock copolymers: Effect of the poly(L-lactide) block length. J. Polym. Sci., Part B: Polym. Phys. 2006, 44,3215-3226.
24Zhou, D.; Sun, J.; Shao, J.; Bian, X.; Huang, S.; Li, G.; Chen,X. Unusual crystallization and melting behavior induced by microphase separation in MPEG-b-PLLA diblock copolymer.Polymer 2015, 80, 123-129.
25Zhao, W.; Li, C. Y.; Wu, C. J.; Liu, X. L.; Mou, Z. H.; Yao, C.G.; Cui, D. M. Synthesis of ultraviolet absorption polylactide via immortal polymerization of rac-lactide initiated by a salanyttrium catalyst. Chinese J. Polym. Sci. 2018, 36, 202-206.
26Yao, F.; Bai, Y.; Zhou, Y.; Liu, C.; Wang, H.; Yao, K. Synthesis and characterization of multiblock copolymers based on Llactic acid, citric acid, and poly(ethylene glycol). J. Polym. Sci.,Part A: Polym. Chem. 2003, 41, 2073-2081.
27Feng, L. D.; Sun, B.; Bian, X. C.; Chen, Z. M.; Chen, X. S. Determination of D-lactate content in poly(lactic acid) using polarimetry. Polym. Test. 2010, 29, 771-776.
28Tsuji, H.; Matsumura, N.; Arakawa, Y. Stereocomplex crystallization and homocrystallization of star-shaped four-armed stereo diblock poly(lactide)s with different L-lactyl unit contents:Isothermal crystallization from the melt. J. Phys. Chem. B 2016, 120, 1183-1193.
29Pan, P.; Kai, W.; Zhu, B.; Dong, T.; Inoue, Y. Polymorphous crystallization and multiple melting behavior of poly(L-lactide):Molecular weight dependence. Macromolecules 2007, 40,6898-6905.
30Pan, P.; Zhu, B.; Kai, W.; Dong, T.; Inoue, Y. Polymorphic transition in disordered poly(L-lactide) crystals induced by annealing at elevated temperatures. Macromolecules 2008, 41,4296-4304.
31Shao, J.; Sun, J.; Bian, X.; Zhou, Y.; Li, G.; Chen, X. The formation and transition behaviors of the mesophase in poly(D-lactide)/poly(L-lactide) blends with low molecular weights.CrystEngComm 2013, 15, 6469-6476.
32Shao, J.; Xiang, S.; Bian, X.; Sun, J.; Li, G.; Chen, X. Remarkable melting behavior of PLA stereocomplex in linear PLLA/PDLA blends. Ind. Eng. Chem. Res. 2015, 54,2246-2253.
33Jeziorny, A. Parameters characterizing the kinetics of the non-isothermal crystallization of poly(ethylene terephthalate) determined by DSC. Polymer 1978, 19, 1142-1144.
34Liu, T.; Mo, Z.; Zhang, H. Nonisothermal crystallization behavior of a novel poly(aryl ether ketone): PEDEKmK. J. Appl.Polym. Sci. 1998, 67, 815-821.
35Vyazovkin, S.; Sbirrazzuoli, N. Isoconversional kinetic analysis of thermally stimulated processes in polymers. Macromol.Rapid Commun. 2006, 27, 1515-1532.
36Vyazovkin, S.; Dollimore, D. Linear and nonlinear procedures in isoconversional computations of the activation energy of nonisothermal reactions in solids. J. Chem. Inf. Model. 1996,36, 42-45.