预聚物光学纯度对立体复合聚乳酸固相缩聚产物的影响
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摘要
采用乳酸为引发剂,辛酸亚锡为催化剂,引发丙交酯开环聚合制备光学纯度不同的预聚物L-聚乳酸(PLLA)和D-聚乳酸(PDLA);将光学纯度相近的预聚物熔融共混后进行固相缩聚,研究了预聚物光学纯度对立体复合聚乳酸固相缩聚产物的影响,分析了固相缩聚产物的链结构、相对分子质量、晶体结构、动态力学性能及降解性能。结果表明,预聚物的光学纯度随着原料单体丙交酯中异构单体含量的增加而降低,预聚物光学纯度的降低使缩聚过程中均相晶体以及立体复合晶体含量降低,从而促进了固相缩聚产物相对分子质量的增加。当预聚物的光学纯度降为95.5%时,固相缩聚产物相对分子质量的增长幅度最大,较未添加异构单体的缩聚产物而言,其相对分子质量提升了97.6%。随着光学纯度的降低,固相缩聚产物的储能模量、耗能模量及玻璃化转变温度下降,吸水率增加。
Prepolymer poly(L-lactide)(PLLA) and poly(D-lactide)(PDLA) having different optical purity were prepared by using lactide as monomer, lactic acid and stannous octoate as initiator and catalyst respectively, solid state polycondensation precursors were obtained by melting blend of PLLA and PDLA with similar optical purity. The effect of the optical purity of the prepolymer on the solid phase polycondensation products of stereocomplex polylactic acid was studied. The chain structure, molecular weight, crystal structure, dynamic mechanical properties and degradation properties of solid state polycondensation products were analyzed. The results show that the optical purity of prepolymer decreases with increase of the isomers content in the monomer. The reduction of the optical purity of the prepolymer reduces the content of both the homogeneous crystal and the stereocomplex crystal in the solid state polycondensation, thus promoting increase of the molecular weight of the solid state polycondensation products. When the optical purity of the prepolymer is reduced to 95.5%, the molecular weight of the solid state polycondensation product is the largest, and the molecular weight of the polymer is 97.6% higher than that of the polycondensation products without isomers. With decrease of the optical purity, the energy storage modulus, energy dissipation modulus, glass transition temperature of solid state polycondensation products are decreasing and the water absorption rate of solid state polycondensation products is increased.
Prepolymer poly(L-lactide)(PLLA) and poly(D-lactide)(PDLA) having different optical purity were prepared by using lactide as monomer, lactic acid and stannous octoate as initiator and catalyst respectively, solid state polycondensation precursors were obtained by melting blend of PLLA and PDLA with similar optical purity. The effect of the optical purity of the prepolymer on the solid phase polycondensation products of stereocomplex polylactic acid was studied. The chain structure, molecular weight, crystal structure, dynamic mechanical properties and degradation properties of solid state polycondensation products were analyzed. The results show that the optical purity of prepolymer decreases with increase of the isomers content in the monomer. The reduction of the optical purity of the prepolymer reduces the content of both the homogeneous crystal and the stereocomplex crystal in the solid state polycondensation, thus promoting increase of the molecular weight of the solid state polycondensation products. When the optical purity of the prepolymer is reduced to 95.5%, the molecular weight of the solid state polycondensation product is the largest, and the molecular weight of the polymer is 97.6% higher than that of the polycondensation products without isomers. With decrease of the optical purity, the energy storage modulus, energy dissipation modulus, glass transition temperature of solid state polycondensation products are decreasing and the water absorption rate of solid state polycondensation products is increased.
引文
[1] 包建娜, 韩理理, 单国荣, 等. 高分子量聚乳酸立体复合结晶的研究进展[J]. 高分子材料科学与工程, 2015, 31(5): 185-190. Bao J N, Han L L, Shan G R, et al. Stereocomplex crystallization of high-molecular-weight poly(lactic acid)[J]. Polymer Materials Science & Engineering, 2015, 31(5): 185-190.
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[3] Bai D, Liu H, Bai H, et al. Low-temperature sintering of stereocomplex-type polylactide nascent powder: effect of crystallinity[J]. Macromolecules, 2017, 50: 7611-7619.
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[6] Tsuji H, Ikada Y. Stereocomplex formation between enantiomeric poly(lactic acids). 9. Stereocomplexation from the melt[J]. Macromolecules, 1993, 26: 6918-6926.
[7] Chen D, Li J, Ren J, et al. Crystal and thermal properties of PLLA/PDLA blends synthesized by direct melt polycondensation[J]. J. Polym. Environ., 2011, 19: 574-581.
[8] Fukushima K, Furuhashi Y, Sogo K, et al. Stereoblock poly(lactic acid): synthesis via solid-state polycondensation of a stereocomplexed mixture of poly(L-lactic acid) and poly(D-lactic acid)[J]. Macromol. Biosci., 2005, 5: 21-29.
[9] Fukushima K, Hirata M, Kimura Y, et al. Synthesis and characterization of stereoblock poly(lactic acid)s with nonequivalent D/L sequence ratios[J]. Macromolecules, 2007, 40: 3049-3055.
[10] Kanno T, Oyama H T, Usugi S, et al. Effects of molecular weight and catalyst on stereoblock formation via solid state polycondensation of poly(lactic acid)[J]. Eur. Polym. J., 2014, 54: 62-70.
[11] Tsuji H, Ikada Y. Stereocomplex formation between enantiomeric poly(lactic acid)s. 6. Binary blends from copolymers [J]. Macromolecules, 1992, 25: 5719-5723.
[12] Fukushima K, Kimura Y. An efficient solid-state polycondensation method for synthesizing stereocomplexed poly(lactic acid)s with high molecular weight[J]. J. Polym. Sci. Part A: Polym. Chem., 2008, 46: 3714-3722.
[13] Rydz, Joanna, Adamus, et al. Degradation of polylactide in paraffin and selected protic media[J]. Polym. Degrad. Stab., 2013, 98: 316-324.
[14] Liu Y, Sun J, Bian X, et al. Melt stereocomplexation from poly( l -lactic acid) and poly(D-lactic acid) with different optical purity[J]. Polym. Degrad. Stab., 2013, 98: 844-852.
[15] Rahaman M H, Tsuji H. Synthesis and characterization of stereo multi-block poly(lactic acid)s with different block lengths by melt polycondensation of poly(L-lactic acid)/poly(D-lactic acid) blends[J]. Macromol. React. Eng., 2012, 6: 446-457.
[16] Fukushima K, Chang Y H, Kimura Y, et al. Enhanced stereocomplex formation of poly(L-lactic acid) and poly(D-lactic acid) in the presence of stereoblock poly(lactic acid)[J]. Macromol. Biosci., 2007, 7: 829-835.
[17] Chang L, Woo E M. A unique meta-form structure in the stereocomplex of poly(D-lactic acid) with low-molecular-weight poly(L-lactic acid)[J]. Macromol. Chem. Phys., 2011, 212: 125-133.
[18] 陈璐, 唐颂超, 夏季, 等. 高耐热PLLA/PDLA共混物的热性能和结晶结构研究[J]. 高分子学报, 2013(8): 1006-1012. Chen L, Tang S C, Xia J, et al. Crystallization structures and thermal properties of high heat-resistance PLLA/PDLA blends[J]. Acta Polymerica Sinica, 2013(8): 1006-1012.
[2] Ikada Y, Jamshidi K, Tsuji H, et al. Stereocomplex formation between enantiomeric poly(lactides)[J]. Macromolecules, 2010, 20: 904-906.
[3] Bai D, Liu H, Bai H, et al. Low-temperature sintering of stereocomplex-type polylactide nascent powder: effect of crystallinity[J]. Macromolecules, 2017, 50: 7611-7619.
[4] Ming R, Yang G, Li Y, et al. Flax fiber-reinforced polylactidestereocomplex composites with enhanced heat resistance and mechanical properties[J]. Polym. Compos., 2015, 38: 472-478.
[5] Kakuta M, Hirata M, Kimura Y, et al. Stereoblock polylactides as high-performance bio-based polymers[J]. Polym. Rev., 2009, 49: 107-140.
[6] Tsuji H, Ikada Y. Stereocomplex formation between enantiomeric poly(lactic acids). 9. Stereocomplexation from the melt[J]. Macromolecules, 1993, 26: 6918-6926.
[7] Chen D, Li J, Ren J, et al. Crystal and thermal properties of PLLA/PDLA blends synthesized by direct melt polycondensation[J]. J. Polym. Environ., 2011, 19: 574-581.
[8] Fukushima K, Furuhashi Y, Sogo K, et al. Stereoblock poly(lactic acid): synthesis via solid-state polycondensation of a stereocomplexed mixture of poly(L-lactic acid) and poly(D-lactic acid)[J]. Macromol. Biosci., 2005, 5: 21-29.
[9] Fukushima K, Hirata M, Kimura Y, et al. Synthesis and characterization of stereoblock poly(lactic acid)s with nonequivalent D/L sequence ratios[J]. Macromolecules, 2007, 40: 3049-3055.
[10] Kanno T, Oyama H T, Usugi S, et al. Effects of molecular weight and catalyst on stereoblock formation via solid state polycondensation of poly(lactic acid)[J]. Eur. Polym. J., 2014, 54: 62-70.
[11] Tsuji H, Ikada Y. Stereocomplex formation between enantiomeric poly(lactic acid)s. 6. Binary blends from copolymers [J]. Macromolecules, 1992, 25: 5719-5723.
[12] Fukushima K, Kimura Y. An efficient solid-state polycondensation method for synthesizing stereocomplexed poly(lactic acid)s with high molecular weight[J]. J. Polym. Sci. Part A: Polym. Chem., 2008, 46: 3714-3722.
[13] Rydz, Joanna, Adamus, et al. Degradation of polylactide in paraffin and selected protic media[J]. Polym. Degrad. Stab., 2013, 98: 316-324.
[14] Liu Y, Sun J, Bian X, et al. Melt stereocomplexation from poly( l -lactic acid) and poly(D-lactic acid) with different optical purity[J]. Polym. Degrad. Stab., 2013, 98: 844-852.
[15] Rahaman M H, Tsuji H. Synthesis and characterization of stereo multi-block poly(lactic acid)s with different block lengths by melt polycondensation of poly(L-lactic acid)/poly(D-lactic acid) blends[J]. Macromol. React. Eng., 2012, 6: 446-457.
[16] Fukushima K, Chang Y H, Kimura Y, et al. Enhanced stereocomplex formation of poly(L-lactic acid) and poly(D-lactic acid) in the presence of stereoblock poly(lactic acid)[J]. Macromol. Biosci., 2007, 7: 829-835.
[17] Chang L, Woo E M. A unique meta-form structure in the stereocomplex of poly(D-lactic acid) with low-molecular-weight poly(L-lactic acid)[J]. Macromol. Chem. Phys., 2011, 212: 125-133.
[18] 陈璐, 唐颂超, 夏季, 等. 高耐热PLLA/PDLA共混物的热性能和结晶结构研究[J]. 高分子学报, 2013(8): 1006-1012. Chen L, Tang S C, Xia J, et al. Crystallization structures and thermal properties of high heat-resistance PLLA/PDLA blends[J]. Acta Polymerica Sinica, 2013(8): 1006-1012.