乳酸基共聚物/蛭石微晶复合材料的制备和性能研究
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摘要
本文以L-乳酸和环氧基改性蛭石为原料,利用原位熔融缩聚法制备了不同蛭石含量的乳酸基共聚物/蛭石(PLLA-co-bis A/MVMTs)纳米复合材料。首先对蛭石原矿进行钠化处理,在机械外力作用下,制得剥分蛭石；通过硅烷偶联剂KH-560改性剥分蛭石,制得表面带有反应性环氧基的官能化剥分蛭石；以环氧基改性蛭石为纳米粒子源,乳酸和己二酸为单体,通过原位熔融缩聚制得含蛭石微晶的羧基封端低分子量聚乳酸预聚体,然后以环氧树脂为扩链剂与制得的低分子量聚乳酸进行反应,成功制备了一种含新型蛭石组装体的高分子量PLLA-co-bis A/MVMTs纳米复合材料。对蛭石的剥分和剥分蛭石官能化改性效果,改性蛭石对L-乳酸熔融缩聚的影响,改性蛭石在L-乳酸熔融缩聚体系的排布和表面接枝和PLLA-co-bis A/MVMTs纳米复合材料的结构、结晶行为、热稳定性和力学性能都进行了较为深入的研究。
用激光粒度仪、X射线衍射(XRD)和透射电镜(TEM)对蛭石的剥分效果进行了表征。结果表明制得的剥分蛭石平均粒径约为100nm,片层厚度为20 nm左右。利用傅里叶红外(FT-IR)、热重分析(TGA)表征了硅烷偶联剂KH-560对剥分蛭石进行环氧基官能化改性效果。结果表明：剥分蛭石的片层上成功引入了环氧基,为制备具具有良好界面相容性的PLLA-co-bis A/MVMTs纳米复合材料打下基础。
通过原位熔融缩聚法成功制备了不同蛭石含量的PLLA-co-bis A/MVMTs纳米复合材料,并探讨了改性蛭石对乳酸熔融缩聚的影响。结果表明,改性蛭石的引入,对PLLA/MVMTs预聚体的分子量基本没有影响；但PLLA-co-bis A/MVMTs基体的分子量下降,并且随着改性蛭石百分含量的增加,分子量持续下降。当改性蛭石含量为0.5%、1.0%、1.5%时,分子量分别下降14%、30%、43%。
通过对制得的PLLA-co-bis A/MVMTs纳米复合材料进行多次离心/洗涤,提取得到复合材料中的改性蛭石(g-VMT),利用傅里叶红外(FT-IR)、热重分析(TGA)和扫描电镜(SEM)研究改性蛭石的表面接枝情况和g-VMT的表观形态。FT-IR表明乳酸基共聚物成功嫁接到改性蛭石表面；TGA表明g-VMT的接枝率为53.3%；SEM表明g-VMT的形态有别于改性蛭石,主要呈现‘棒状’和‘饼状’两种特殊形态；利用透射电镜(TEM)表征改性蛭石在PLLA-co-bis A基体中分散或排布情况,结果表明一种新型的蛭石组装体存在于PLLA-co-bis A/MVMTs纳米复合材料基体中,无机-有机相显现出优良的界面相容性,这种特殊的界面结构将影响到聚合物结晶行为、热稳定性和力学性能。
利用差热扫描量热分析仪(DSC)和偏光显微镜(POM)研究了改性蛭石微晶对PLLA-co-bis A/MVMTs纳米复合材料结晶行为的影响。结果表明,随着改性蛭石微晶的加入,PLLA-co-bis A/MVMTs纳米复合材料的玻璃化温度(Tg)提高；结晶度和结晶速率得到显著提高；晶核密度增大、晶粒尺寸降低,证明改性蛭石的加入提高了聚乳酸的结晶速率。
TGA测试表明,相比较于纯的PLLA-co-bis A共聚物,PLLA-co-bis A/MVMTs纳米复合材料具有更好的热稳定性。当改性蛭石含量为1.5%时,其复合材料的Tonset,Tend,Tmax分别提高了13.8℃,9.3℃,2.1℃。力学性能测试表明,改性蛭石的加入没有影响PLLA-co-bis A共聚物的断裂强度和断裂伸长率。
In this thesis, in situ melt polyeondensation of L-LA in the presenee of epoxy-modified vermiculites (MVMTs) has been proposed as a novel approach to prepare Poly(L-lactic acid)-co-bisphenol-A epoxy resin/modified vermiculite (PLLA-co-bis A/MVMTs) nanocomposites for the first time.
Vermiculates containing epoxy groups were successfully prepared by reaching KH-560 with vermiculites which had previouly been exfoliated by cation exchange and mechanical force. Then carboxyl-terminated PLLA/MVMTs prepolymer and PLLA-co-bis A/MVMTs chain extended products were synthesized by in situ polycondensation. The effect of MVMTs on the molecular weight, nanostructure, crystallization behaviors, thermal stability and mechanical properties of the PLLA-co-bis A/MVMTs nanocomposite was investigated in detail.
Laser particle size analyzer, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were introduced to characterize vermiculite exfoliation. The results showed that a particle size of 100 nm, thickness of 20 nm around exfoliated vermiculite was successfully prepared. We attached epoxy groups onto vermiculite surface via siloxane linkage by the use of KH-560. It could be confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed about 4.01% coupling agents were grafted to MVMTs surface.
The introduction of modified vermiculite had no effect on the molecular weight of PLLA/MVMTs prepolymer, but the molecular weight of PLLA-co-bis A/MVMTs matrix decreased. As the percentage of modified vermiculite content increased, the molecular weight continued to declined. The molecular weight decreased by 14%,30%,43% when the modified vermiculite content of 0.5%,1%,1.5%, respectively.
Vermiculite grafted with polymer (g-VMT) in PLLA-co-bis A/MVMTs nanocomposites was isolated from free polymer via repeated dispersion/centrifugation processes and characterized. Formation of chemical bonding between PLLA-co-bis A chains and surface epoxy groups from MVMTs was detected by FT-IR. Calculations based on TGA revealed that more than 53.3% polymers were successfully grafted into MVMTs. SEM showed that the g-VMT had special'rod' and 'pie' forms. Morphological images showed a novel assembly of MVMT nanocrystals in the PLLA-co-bis A matrix and demonstrated a strong interfacial interaction between them. This special interface structure will affect crystallization behavior, thermal stability and mechanical properties of PLLA-co-bis A/MVMTs nanocomposites.
Differential scanning calorimetry calorimetry (DSC) and Polarizing optical microscopy (POM) were introduced to characterize the crystallization behavior of PLLA-co-bis A/MVMTs nanocomposites. The results showed that overall crystallization rate of nanocomposite elevated and spherulite size decresed in the presence of vermiculite particles. PLLA-co-bis A/MVMTs nanocomposites exhibited increased crystallinity and glass transition temperature (Tg), compared with pure PLLA-co-bis A.
TGA tests showed that PLLA-co-bis A/MVMTs nanocomposites had better thermal stability, compared to pure PLLA-co-bis A copolymer. When MVMTs content of 1.5%, the nanocomposite Tonset, Tend,Tmax increased by 13.8℃,9.3℃,2.1℃. Modified vermiculiate did not play a negative role in improving the breaking strength and elongation at break of the PLLA-co-bis A copolymers.
用激光粒度仪、X射线衍射(XRD)和透射电镜(TEM)对蛭石的剥分效果进行了表征。结果表明制得的剥分蛭石平均粒径约为100nm,片层厚度为20 nm左右。利用傅里叶红外(FT-IR)、热重分析(TGA)表征了硅烷偶联剂KH-560对剥分蛭石进行环氧基官能化改性效果。结果表明：剥分蛭石的片层上成功引入了环氧基,为制备具具有良好界面相容性的PLLA-co-bis A/MVMTs纳米复合材料打下基础。
通过原位熔融缩聚法成功制备了不同蛭石含量的PLLA-co-bis A/MVMTs纳米复合材料,并探讨了改性蛭石对乳酸熔融缩聚的影响。结果表明,改性蛭石的引入,对PLLA/MVMTs预聚体的分子量基本没有影响；但PLLA-co-bis A/MVMTs基体的分子量下降,并且随着改性蛭石百分含量的增加,分子量持续下降。当改性蛭石含量为0.5%、1.0%、1.5%时,分子量分别下降14%、30%、43%。
通过对制得的PLLA-co-bis A/MVMTs纳米复合材料进行多次离心/洗涤,提取得到复合材料中的改性蛭石(g-VMT),利用傅里叶红外(FT-IR)、热重分析(TGA)和扫描电镜(SEM)研究改性蛭石的表面接枝情况和g-VMT的表观形态。FT-IR表明乳酸基共聚物成功嫁接到改性蛭石表面；TGA表明g-VMT的接枝率为53.3%；SEM表明g-VMT的形态有别于改性蛭石,主要呈现‘棒状’和‘饼状’两种特殊形态；利用透射电镜(TEM)表征改性蛭石在PLLA-co-bis A基体中分散或排布情况,结果表明一种新型的蛭石组装体存在于PLLA-co-bis A/MVMTs纳米复合材料基体中,无机-有机相显现出优良的界面相容性,这种特殊的界面结构将影响到聚合物结晶行为、热稳定性和力学性能。
利用差热扫描量热分析仪(DSC)和偏光显微镜(POM)研究了改性蛭石微晶对PLLA-co-bis A/MVMTs纳米复合材料结晶行为的影响。结果表明,随着改性蛭石微晶的加入,PLLA-co-bis A/MVMTs纳米复合材料的玻璃化温度(Tg)提高；结晶度和结晶速率得到显著提高；晶核密度增大、晶粒尺寸降低,证明改性蛭石的加入提高了聚乳酸的结晶速率。
TGA测试表明,相比较于纯的PLLA-co-bis A共聚物,PLLA-co-bis A/MVMTs纳米复合材料具有更好的热稳定性。当改性蛭石含量为1.5%时,其复合材料的Tonset,Tend,Tmax分别提高了13.8℃,9.3℃,2.1℃。力学性能测试表明,改性蛭石的加入没有影响PLLA-co-bis A共聚物的断裂强度和断裂伸长率。
In this thesis, in situ melt polyeondensation of L-LA in the presenee of epoxy-modified vermiculites (MVMTs) has been proposed as a novel approach to prepare Poly(L-lactic acid)-co-bisphenol-A epoxy resin/modified vermiculite (PLLA-co-bis A/MVMTs) nanocomposites for the first time.
Vermiculates containing epoxy groups were successfully prepared by reaching KH-560 with vermiculites which had previouly been exfoliated by cation exchange and mechanical force. Then carboxyl-terminated PLLA/MVMTs prepolymer and PLLA-co-bis A/MVMTs chain extended products were synthesized by in situ polycondensation. The effect of MVMTs on the molecular weight, nanostructure, crystallization behaviors, thermal stability and mechanical properties of the PLLA-co-bis A/MVMTs nanocomposite was investigated in detail.
Laser particle size analyzer, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were introduced to characterize vermiculite exfoliation. The results showed that a particle size of 100 nm, thickness of 20 nm around exfoliated vermiculite was successfully prepared. We attached epoxy groups onto vermiculite surface via siloxane linkage by the use of KH-560. It could be confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) showed about 4.01% coupling agents were grafted to MVMTs surface.
The introduction of modified vermiculite had no effect on the molecular weight of PLLA/MVMTs prepolymer, but the molecular weight of PLLA-co-bis A/MVMTs matrix decreased. As the percentage of modified vermiculite content increased, the molecular weight continued to declined. The molecular weight decreased by 14%,30%,43% when the modified vermiculite content of 0.5%,1%,1.5%, respectively.
Vermiculite grafted with polymer (g-VMT) in PLLA-co-bis A/MVMTs nanocomposites was isolated from free polymer via repeated dispersion/centrifugation processes and characterized. Formation of chemical bonding between PLLA-co-bis A chains and surface epoxy groups from MVMTs was detected by FT-IR. Calculations based on TGA revealed that more than 53.3% polymers were successfully grafted into MVMTs. SEM showed that the g-VMT had special'rod' and 'pie' forms. Morphological images showed a novel assembly of MVMT nanocrystals in the PLLA-co-bis A matrix and demonstrated a strong interfacial interaction between them. This special interface structure will affect crystallization behavior, thermal stability and mechanical properties of PLLA-co-bis A/MVMTs nanocomposites.
Differential scanning calorimetry calorimetry (DSC) and Polarizing optical microscopy (POM) were introduced to characterize the crystallization behavior of PLLA-co-bis A/MVMTs nanocomposites. The results showed that overall crystallization rate of nanocomposite elevated and spherulite size decresed in the presence of vermiculite particles. PLLA-co-bis A/MVMTs nanocomposites exhibited increased crystallinity and glass transition temperature (Tg), compared with pure PLLA-co-bis A.
TGA tests showed that PLLA-co-bis A/MVMTs nanocomposites had better thermal stability, compared to pure PLLA-co-bis A copolymer. When MVMTs content of 1.5%, the nanocomposite Tonset, Tend,Tmax increased by 13.8℃,9.3℃,2.1℃. Modified vermiculiate did not play a negative role in improving the breaking strength and elongation at break of the PLLA-co-bis A copolymers.
引文
[1]冯静等.几种高分子材料的生物降解进展研究[J].塑料科技,2011,39(2):94-99.
[2]Nampoothiri K M, Nair N R, John R P, et al. An overview of the recent developments in polylactide(PLA) research[J]. Bioresour Technol,2010,101:8493-8501.
[3]Gupta A P, Kumar V. New emerging trends in synthetic biodegradable polymers-Polylactide:A critique[J]. Eur Polym J,2007,43:4053-4074.
[4]Kricheldorf H R. Syntheses and application of polylacticdes[J]. Chemosphere,2001,43: 49-54.
[5]Ajioka M, Enomoto K, Suzuki K, et al. The basic properties of poly(lactic acid) produced by the direct condensation polymerization of lactic acid[J]. J Environ Polym Degrad,1995,3(4): 225-234.
[6]任杰,王秦峰.一种乳酸直接缩聚制备聚乳酸的聚合反应装置：中国,2641046[P].2004-09-15.
[7]黎莉,唐颂超,王庆海等.溶液共沸法合成较高分子量的聚乳酸[J].华东理工大学学报(自然科学版),2006,32(6)：672-675.
[8]汪朝阳,赵耀明,王浚等.外消旋乳酸直接聚合—二异氰酸酯溶液扩连反应机理[J].化工学报,2007,58(3)：638-645.
[9]张爱军,杨青芳,叶佳佳等.聚乳酸熔融缩聚的研究[J].中国粘胶剂,2007,16(8):31-35.
[10]Li B H, Yang M C. Improvement of thermal and mechanical properties of poly(L-lactic acid) with 4,4-methylene diphenyl diisocyanate[J]. Polym Adv Technol,2006,17:439-443.
[11]王玉忠等.一种聚乳酸嵌段共聚物及其制备方法：中国,101024696[P].2007-08-29.
[12]余木火等.一种高分子量聚乳酸的制备方法：中国,1757659[P].2006-04-12.
[13]Moon S I, Lee C W, Miyamoto M, et al. Melt polycondensation of L-lactic acid with Sn(II) catalysts activated by various proton acid:A direct manufacturing route to Poly(L-lactic acid) with high molecular weight[J]. J Polym Sci Part A:Polym Chem,2000,38(9):1673-1679.
[14]Moon S 1, Lee C W, Taniguchil, et al. Melt/solid polycondensation of L-lactic:an alternative route to Poly(L-lactic acid) with high molecular weight[J]. Polymer,2001,42(11): 5059-5062.
[15]邢云杰,袁茂全,茅惠萍等.新型生物降解材料—含氢键聚乳酸的制备[J].上海化工,2006,31(3)：15-18.
[16]侯文婷,唐颂超,蒲文亮等.L-聚乳酸固相缩聚的工艺研究[J].高分子通报,2011,05:82-86.
[17]Cartier L, Okihara T, Ikada Y, et al. Epitaxial crystallization and crystalline polymorphism of polylactides[J]. Polymer,2000,41(25):8909-8919.
[18]李旭娟,李忠明.聚乳酸结晶的研究进展[J].中国塑料,2006,20(10):6-11.
[19]Yu H, Huang N, Wang C, et al. Modeling of poly(L-lactide) thermal degradation: Theoretical prediction of molecular weight and polydispersity index[J]. J Appl Polym Sci, 2003,88:2557-2562.
[20]Fan Y, Nishida H, Shirai Y, et al. Thermal stability of poly (L-lactide):influence of end protection by acetyl group[J]. Polym Degrad Stab,2004,84:143-149.
[21]Joziasse C A P, Veenstra H, Topp M D C, et al. Rubber toughened linear and star-shaped poly(d,1-lactide-co-glycolide):synthesis, properties and in vitro degradation[J]. Polymer, 1998,39(2):467-473.
[22]Jeon O, Lee S H, Kim H S, et al, Synthesis and characterization of Poly(L-lactide)-Poly(ε-caprolactone) multiblock copolymers[J]. Macromolecules,2003, 36(15):5585-5592.
[23]周海.乳酸与ω-氨基酸的直接共缩聚研究及共聚物应用初探[D].上海：复旦大学,2009.
[24]任洁莹,李勇锋,高世岗等.聚己二酸丙三醇酯增韧改性聚乳酸的研究[J].化工新型材料,2008,36(9)：69-70.
[25]Ogata N, Jimenez G, Kawai H, et al. Structure and thermal/mechanical properties of poly(L-lactide)-clay blend[J]. J Polym Sci:Part B:Polym Phys,1997,35(2):389-396.
[26]Kim B H, Jung J H, Hong S H, et al. Nanocomposite of Polyaniline and Na+-Montmorillonite clay[J]. Macromolecules,2002,35:1419-1423.
[27]Ray S S, Maiti P, Okamoto M, et al. New polylactide/layered silicate nanocomposites.1. Preparation, characterization, and properties [J]. Macromolecules,2002,35(8):3104-3110.
[28]Lee S, Kim C H, Park J K. Improvement of processability of clay/polylactide nanocomposites by a combinational method:In situ polymerization of L-lactide and melt compounding of polylactide[J]. J App Polym Sci,2006,101:1664-1669.
[29]Chen G X, Kim H S, Shim J H, et al. Role of epoxy groups on clay surface in the improvement of morphology of Poly(L-lactide)/clay composites[J]. Macromolecules,2005, 38(9):3738-3744.
[30]Paul M A, Delcourt C, Alexander M, et al. (Plasticized) polylactide/(organo-) clay nanocomposites by in situ intercalative polymerization[J]. Macromol Chem Phys,2005,206: 484-498.
[31]Pluta M. Melt compounding of polylactide/organoclay:structure and properties of nanocomposites[J]. J Polym Sci:Part B:Polym Phys,2006,44:3392-3405.
[32]Paul M A, Alexandre M, Degee P, et al. Exfoliated polylactide/clay nanocomposites by in-situ coordination-insertion polymerization[J]. Macromol Rapid Commun,2003,24:561-566.
[33]Joubert M, Delaite C, Elodie B L, et al. Ring-opening polymerization of ε-caprolactone and L-lactide from silica nanocomposites surfac[J]. J Polym Sci:Part A:Polym Chem,2004,42: 1976-1984.
[34]Yan S, Yin J, Yang Y, et al. Surface-grafted silica linked with L-lactic acid oligomer:A novel nanofiller to improve the performance of biodegradable poly(L-lactide)[J]. Polymer,2007, 48(6):1688-1694.
[35]Li Y, Chen C, Li J, et al. Synthesis and characterization of bionanocomposites of poly(lactic acid) and TiO2 nanowires by in situ polymerization[J]. Polymer,2011,52:2367-2375.
[36]满长阵,张春梅,王维维等.聚乳酸/TiO2杂化薄膜的抗紫外光性能[J].高分子材料科学与工程,2010,26(12)：99-107.
[37]Hong Z H, Qiu X Y, Sun J R, et al. Grafting polymerization of L-lactide on the surface of hydroxyapatite nano-crystals[J]. Polymer,2004,45:6699-6706.
[38]Chen G X, Kim H S, Park B H, et al. Controlled functionalization of multiwalled carbon nanotubes with various molecule-weight poly(L-lactic acid)[J]. J Phys Chem B,2005,109: 22237-22243.
[39]田蓉,王贤保,陈蓉等.可降解碳纳米管/聚乳酸复合材料的制备及性能[J].复合材料学报,2011,28(1)：26-30.
[40]宋文会,郑震,汤伟亮等.原位聚合制备碳纳米管与聚乳酸复合物[J].2007年全国高分子学术论文报告会论文摘要集(上册).2007.
[41]Luo Y B, Wang X L, Xu D Y, et al. Preparation and characterization of poly(lactic acid)-grafted TiO2 nanoparticles with improved dispersions[J]. Appl Surf Sci,2009,255: 6795-6801.
[42]Xu X, Li B, Lu H, et al. The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties[J]. Appl Surf Sci,2007,254: 1456-1462.
[43]阚红.介观尺度片状蛭石与耐高温聚合物复合膜的制备及性能研究[D].上海：东华大学,2008.
[44]Li Y, Guan H M, Chung T S, et al, Effects of novel silane modification of zeolite surface on polymer chain rigidification and partial pore blockage in polyethersulfone(PES)-zeolite A mixed matrix membranes[J]. J Membrane Sci,2006,275:17-28.
[45]徐红.高相对分子质量聚乳酸共聚物的合成及性能研究[D].上海：东华大学,2006.
[46]Kricheldorf H R, Lee S R, Bush S. Macrocyclic polymerization of lactides with cyclic Bu2Sn initiators derived from 1,2-ethanediol,2-mercaptoethanol, and 1,2-dimercaptoethane[J]. Macromolecules,1996,29(5):1375-1381.
[47]Xu X, Li B, Lu H, et al.The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties[J]. Appli Surf Sci,2007,254: 1456-1462.
[48]Wang W S, Chen H S, Wu Y W, et al. Properties of novel epoxy/clay nanocomposites prepared with a reactive phosphorus-containing organoclay[J]. Polymer,2008,49: 4826-4836.
[49]马传国,于英俊.碳纳米管的偶联剂修饰及其在环氧树脂复合材料中的应用[J].复合材料学报,2010,27(3)：22-28.
[50]Li Y, Sun X S. Preparation and characterization of polymer-inorganic nanocomposites by in situ melt polycondensation of L-lactic acid and surface-hydroxylated MgO[J]. Biomacromolecules,2010,11(7):1847-1855.
[51]Balazs A C, Emrick T, Russell T P. Nanoparticle polymer composites:where two small worlds meet[J]. Science,2006,314:1107-1110.
[52]Lee J Y, Thompson R B, Jasnow D, et al. Effect of Nanoscopic Particles on the Mesophase Structure of Diblock Copolymer[J]. Macromolecules,2002,35:4855-4858.
[53]Lee J Y, Thompson R B, Jasnow D, et al, Entropically driven formation of hierarchically ordered nanocomposites[J]. Phys Rev Lett,2002,89(15):155503.
[54]Zhang J, Lou J, Ilias S, et al. Thermal properties of poly(lactic acid) fumed silica nanocomposites:Experiments and molecular dynamics simulations[J]. Polymer,2008,49: 2381-2386.
[55]Zhou Q, Xanthos M, Nanosize and microsize clay effects on the kinetics of the thermal degradation of polylactide[J]. Polym Degrad Stabil,2009,94:327-338.
[56]Nam J Y, Ray S S, Okamoto M. Crystallization behavior and morphology of biodegradable polylactide/layered silicate nanocomposite[J], Macromolecules,2003,36:7126-7131.
[57]曹丹.聚乳酸/Si02纳米复合材料的原位缩聚法制备与表征[D].上海：浙江大学,2007.
[58]Miyata T, Masuko T. Crystallization behaviour of Poly(L-lactide)[J]. Polymer,1998,39(22): 5515-5521.
[59]Yan S F, Yin J B, Yang Y, et al. Surface-grafted silica linked with L-lactic acid oligomer:A novel nanofiller to improve the performance of biodegradable poly(L-lactide)[J]. Polymer, 2007,48:1688-1694.
[60]Yasuniwa M, Tsubakihara S, Sugimoto Y, et al, Thermal analysis of the double-melting behavior of poly(L-lactic acid)[J]. J Polym Sci:Part B:Polym Phys,2004,42:25-32.
[61]Hong Z, Zhang P, He C, et al. Nano-composite of poly(L-lactide) and surface grafted hydroxyapatite:Mechanical properties and biocompatibility[J]. Biomaterials,2005,26: 6296-6304.
[62]Pluta M, Galeski A, Alexandre M, et al. Polylactide/montmorillonite nanocomposites and microcomposites prepared by melt blending:Structure and some physical properties[J]. J Appli Polym Sci,2002,86(6):1497-1506.
[63]Auras R, Harte B, Selke S. An overview of polylactides as packaging materials[J]. Macromol Biosci,2004,4:835-864.
[64]Chrissafisa K, Bikiaris D, Can nanoparticles really enhance thermal stability of polymers? Part I:An overview on thermal decomposition of addition polymers[J], Thermochim Acta, 2011,523:1-24.
[65]Zhou Q Y, Xanthos M, Nanosize and microsize clay effects on the kinetics of the thermal degradation of polylactides[J]. Polym Degrad stab,2009,94:327-338.
[2]Nampoothiri K M, Nair N R, John R P, et al. An overview of the recent developments in polylactide(PLA) research[J]. Bioresour Technol,2010,101:8493-8501.
[3]Gupta A P, Kumar V. New emerging trends in synthetic biodegradable polymers-Polylactide:A critique[J]. Eur Polym J,2007,43:4053-4074.
[4]Kricheldorf H R. Syntheses and application of polylacticdes[J]. Chemosphere,2001,43: 49-54.
[5]Ajioka M, Enomoto K, Suzuki K, et al. The basic properties of poly(lactic acid) produced by the direct condensation polymerization of lactic acid[J]. J Environ Polym Degrad,1995,3(4): 225-234.
[6]任杰,王秦峰.一种乳酸直接缩聚制备聚乳酸的聚合反应装置：中国,2641046[P].2004-09-15.
[7]黎莉,唐颂超,王庆海等.溶液共沸法合成较高分子量的聚乳酸[J].华东理工大学学报(自然科学版),2006,32(6)：672-675.
[8]汪朝阳,赵耀明,王浚等.外消旋乳酸直接聚合—二异氰酸酯溶液扩连反应机理[J].化工学报,2007,58(3)：638-645.
[9]张爱军,杨青芳,叶佳佳等.聚乳酸熔融缩聚的研究[J].中国粘胶剂,2007,16(8):31-35.
[10]Li B H, Yang M C. Improvement of thermal and mechanical properties of poly(L-lactic acid) with 4,4-methylene diphenyl diisocyanate[J]. Polym Adv Technol,2006,17:439-443.
[11]王玉忠等.一种聚乳酸嵌段共聚物及其制备方法：中国,101024696[P].2007-08-29.
[12]余木火等.一种高分子量聚乳酸的制备方法：中国,1757659[P].2006-04-12.
[13]Moon S I, Lee C W, Miyamoto M, et al. Melt polycondensation of L-lactic acid with Sn(II) catalysts activated by various proton acid:A direct manufacturing route to Poly(L-lactic acid) with high molecular weight[J]. J Polym Sci Part A:Polym Chem,2000,38(9):1673-1679.
[14]Moon S 1, Lee C W, Taniguchil, et al. Melt/solid polycondensation of L-lactic:an alternative route to Poly(L-lactic acid) with high molecular weight[J]. Polymer,2001,42(11): 5059-5062.
[15]邢云杰,袁茂全,茅惠萍等.新型生物降解材料—含氢键聚乳酸的制备[J].上海化工,2006,31(3)：15-18.
[16]侯文婷,唐颂超,蒲文亮等.L-聚乳酸固相缩聚的工艺研究[J].高分子通报,2011,05:82-86.
[17]Cartier L, Okihara T, Ikada Y, et al. Epitaxial crystallization and crystalline polymorphism of polylactides[J]. Polymer,2000,41(25):8909-8919.
[18]李旭娟,李忠明.聚乳酸结晶的研究进展[J].中国塑料,2006,20(10):6-11.
[19]Yu H, Huang N, Wang C, et al. Modeling of poly(L-lactide) thermal degradation: Theoretical prediction of molecular weight and polydispersity index[J]. J Appl Polym Sci, 2003,88:2557-2562.
[20]Fan Y, Nishida H, Shirai Y, et al. Thermal stability of poly (L-lactide):influence of end protection by acetyl group[J]. Polym Degrad Stab,2004,84:143-149.
[21]Joziasse C A P, Veenstra H, Topp M D C, et al. Rubber toughened linear and star-shaped poly(d,1-lactide-co-glycolide):synthesis, properties and in vitro degradation[J]. Polymer, 1998,39(2):467-473.
[22]Jeon O, Lee S H, Kim H S, et al, Synthesis and characterization of Poly(L-lactide)-Poly(ε-caprolactone) multiblock copolymers[J]. Macromolecules,2003, 36(15):5585-5592.
[23]周海.乳酸与ω-氨基酸的直接共缩聚研究及共聚物应用初探[D].上海：复旦大学,2009.
[24]任洁莹,李勇锋,高世岗等.聚己二酸丙三醇酯增韧改性聚乳酸的研究[J].化工新型材料,2008,36(9)：69-70.
[25]Ogata N, Jimenez G, Kawai H, et al. Structure and thermal/mechanical properties of poly(L-lactide)-clay blend[J]. J Polym Sci:Part B:Polym Phys,1997,35(2):389-396.
[26]Kim B H, Jung J H, Hong S H, et al. Nanocomposite of Polyaniline and Na+-Montmorillonite clay[J]. Macromolecules,2002,35:1419-1423.
[27]Ray S S, Maiti P, Okamoto M, et al. New polylactide/layered silicate nanocomposites.1. Preparation, characterization, and properties [J]. Macromolecules,2002,35(8):3104-3110.
[28]Lee S, Kim C H, Park J K. Improvement of processability of clay/polylactide nanocomposites by a combinational method:In situ polymerization of L-lactide and melt compounding of polylactide[J]. J App Polym Sci,2006,101:1664-1669.
[29]Chen G X, Kim H S, Shim J H, et al. Role of epoxy groups on clay surface in the improvement of morphology of Poly(L-lactide)/clay composites[J]. Macromolecules,2005, 38(9):3738-3744.
[30]Paul M A, Delcourt C, Alexander M, et al. (Plasticized) polylactide/(organo-) clay nanocomposites by in situ intercalative polymerization[J]. Macromol Chem Phys,2005,206: 484-498.
[31]Pluta M. Melt compounding of polylactide/organoclay:structure and properties of nanocomposites[J]. J Polym Sci:Part B:Polym Phys,2006,44:3392-3405.
[32]Paul M A, Alexandre M, Degee P, et al. Exfoliated polylactide/clay nanocomposites by in-situ coordination-insertion polymerization[J]. Macromol Rapid Commun,2003,24:561-566.
[33]Joubert M, Delaite C, Elodie B L, et al. Ring-opening polymerization of ε-caprolactone and L-lactide from silica nanocomposites surfac[J]. J Polym Sci:Part A:Polym Chem,2004,42: 1976-1984.
[34]Yan S, Yin J, Yang Y, et al. Surface-grafted silica linked with L-lactic acid oligomer:A novel nanofiller to improve the performance of biodegradable poly(L-lactide)[J]. Polymer,2007, 48(6):1688-1694.
[35]Li Y, Chen C, Li J, et al. Synthesis and characterization of bionanocomposites of poly(lactic acid) and TiO2 nanowires by in situ polymerization[J]. Polymer,2011,52:2367-2375.
[36]满长阵,张春梅,王维维等.聚乳酸/TiO2杂化薄膜的抗紫外光性能[J].高分子材料科学与工程,2010,26(12)：99-107.
[37]Hong Z H, Qiu X Y, Sun J R, et al. Grafting polymerization of L-lactide on the surface of hydroxyapatite nano-crystals[J]. Polymer,2004,45:6699-6706.
[38]Chen G X, Kim H S, Park B H, et al. Controlled functionalization of multiwalled carbon nanotubes with various molecule-weight poly(L-lactic acid)[J]. J Phys Chem B,2005,109: 22237-22243.
[39]田蓉,王贤保,陈蓉等.可降解碳纳米管/聚乳酸复合材料的制备及性能[J].复合材料学报,2011,28(1)：26-30.
[40]宋文会,郑震,汤伟亮等.原位聚合制备碳纳米管与聚乳酸复合物[J].2007年全国高分子学术论文报告会论文摘要集(上册).2007.
[41]Luo Y B, Wang X L, Xu D Y, et al. Preparation and characterization of poly(lactic acid)-grafted TiO2 nanoparticles with improved dispersions[J]. Appl Surf Sci,2009,255: 6795-6801.
[42]Xu X, Li B, Lu H, et al. The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties[J]. Appl Surf Sci,2007,254: 1456-1462.
[43]阚红.介观尺度片状蛭石与耐高温聚合物复合膜的制备及性能研究[D].上海：东华大学,2008.
[44]Li Y, Guan H M, Chung T S, et al, Effects of novel silane modification of zeolite surface on polymer chain rigidification and partial pore blockage in polyethersulfone(PES)-zeolite A mixed matrix membranes[J]. J Membrane Sci,2006,275:17-28.
[45]徐红.高相对分子质量聚乳酸共聚物的合成及性能研究[D].上海：东华大学,2006.
[46]Kricheldorf H R, Lee S R, Bush S. Macrocyclic polymerization of lactides with cyclic Bu2Sn initiators derived from 1,2-ethanediol,2-mercaptoethanol, and 1,2-dimercaptoethane[J]. Macromolecules,1996,29(5):1375-1381.
[47]Xu X, Li B, Lu H, et al.The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties[J]. Appli Surf Sci,2007,254: 1456-1462.
[48]Wang W S, Chen H S, Wu Y W, et al. Properties of novel epoxy/clay nanocomposites prepared with a reactive phosphorus-containing organoclay[J]. Polymer,2008,49: 4826-4836.
[49]马传国,于英俊.碳纳米管的偶联剂修饰及其在环氧树脂复合材料中的应用[J].复合材料学报,2010,27(3)：22-28.
[50]Li Y, Sun X S. Preparation and characterization of polymer-inorganic nanocomposites by in situ melt polycondensation of L-lactic acid and surface-hydroxylated MgO[J]. Biomacromolecules,2010,11(7):1847-1855.
[51]Balazs A C, Emrick T, Russell T P. Nanoparticle polymer composites:where two small worlds meet[J]. Science,2006,314:1107-1110.
[52]Lee J Y, Thompson R B, Jasnow D, et al. Effect of Nanoscopic Particles on the Mesophase Structure of Diblock Copolymer[J]. Macromolecules,2002,35:4855-4858.
[53]Lee J Y, Thompson R B, Jasnow D, et al, Entropically driven formation of hierarchically ordered nanocomposites[J]. Phys Rev Lett,2002,89(15):155503.
[54]Zhang J, Lou J, Ilias S, et al. Thermal properties of poly(lactic acid) fumed silica nanocomposites:Experiments and molecular dynamics simulations[J]. Polymer,2008,49: 2381-2386.
[55]Zhou Q, Xanthos M, Nanosize and microsize clay effects on the kinetics of the thermal degradation of polylactide[J]. Polym Degrad Stabil,2009,94:327-338.
[56]Nam J Y, Ray S S, Okamoto M. Crystallization behavior and morphology of biodegradable polylactide/layered silicate nanocomposite[J], Macromolecules,2003,36:7126-7131.
[57]曹丹.聚乳酸/Si02纳米复合材料的原位缩聚法制备与表征[D].上海：浙江大学,2007.
[58]Miyata T, Masuko T. Crystallization behaviour of Poly(L-lactide)[J]. Polymer,1998,39(22): 5515-5521.
[59]Yan S F, Yin J B, Yang Y, et al. Surface-grafted silica linked with L-lactic acid oligomer:A novel nanofiller to improve the performance of biodegradable poly(L-lactide)[J]. Polymer, 2007,48:1688-1694.
[60]Yasuniwa M, Tsubakihara S, Sugimoto Y, et al, Thermal analysis of the double-melting behavior of poly(L-lactic acid)[J]. J Polym Sci:Part B:Polym Phys,2004,42:25-32.
[61]Hong Z, Zhang P, He C, et al. Nano-composite of poly(L-lactide) and surface grafted hydroxyapatite:Mechanical properties and biocompatibility[J]. Biomaterials,2005,26: 6296-6304.
[62]Pluta M, Galeski A, Alexandre M, et al. Polylactide/montmorillonite nanocomposites and microcomposites prepared by melt blending:Structure and some physical properties[J]. J Appli Polym Sci,2002,86(6):1497-1506.
[63]Auras R, Harte B, Selke S. An overview of polylactides as packaging materials[J]. Macromol Biosci,2004,4:835-864.
[64]Chrissafisa K, Bikiaris D, Can nanoparticles really enhance thermal stability of polymers? Part I:An overview on thermal decomposition of addition polymers[J], Thermochim Acta, 2011,523:1-24.
[65]Zhou Q Y, Xanthos M, Nanosize and microsize clay effects on the kinetics of the thermal degradation of polylactides[J]. Polym Degrad stab,2009,94:327-338.