高分子量聚L-乳酸的合成和表征

采用丙交酯开环聚合合成聚L-乳酸(PLLA),研究了引发剂用量、聚合时间对聚L-乳酸分子量的影响.采用FTIR、DSC、TG分析方法对聚乳酸的结构和热性能加以表征.研究结果表明通过对聚合时间以及引发剂用量的控制,合成出高分子量聚L-乳酸.FTIR分析结果证实了聚L-乳酸的结构,DSC分析表明合成出的聚L-乳酸玻璃化转变温度为62℃,结晶度达到42.3%;TG分析表明聚L-乳酸热分解温度为299℃.     

低温常压下高分子量左旋聚乳酸的微波合成及表征

以辛酸亚锡为催化剂低温常压下引发左旋丙交酯(LLA)开环聚合,快速高效地合成了性能良好的高分子量左旋聚乳酸(PLLA).通过正交实验研究了催化剂用量、反应温度和时间对产物分子量的影响,在催化剂用量0.21%(质量分数),反应温度100℃,反应时间60min时得到产物粘均分子量高达16.21×104.通过红外光谱(FTIR)、核磁共振氢谱(1H-NMR)对产物的结构进行分析,结果证明利用微波能有效地合成左旋聚乳酸,通过差式扫描量热(DSC)、X衍射(XRD)、旋光度和力学性能对左旋聚乳酸膜的性能进行表征,结果显示产物纯净,其结晶度为85.6%,光学纯度为98%,有良好的力学性能.     

可生物降解PLA—PEG嵌段共聚物的形态结构研究

分别以氯化亚锡、三异丁基铝-水-磷酸为催化剂,合成了含不同聚醚链段长度的聚乳酸-聚乙二醇(PLA-PEG)嵌段共聚物。以~1H-NMR、GPC、DSC、TEM等研究了聚合物处理方式、聚醚链段长度及不同分子量、不同组成的分级级分对共聚物形态结构的影响。结果表明,在两种不同催化剂下,所得共聚物的形态结构明显不同。     

应用于心血管支架表面涂层聚乳酸及其共聚物的合成

聚乳酸及其共聚物的制备采用两步法合成,即以DL-乳酸和乙醇酸为原料,制得了高纯度聚合单体丙交酯和乙交酯;再以辛酸亚锡为引发剂,月桂醇为链转移剂(即分子量调节剂),在高真空下开环本体聚合制得了一系列的不同分子量的聚乳酸均聚物和不同配比的共聚物.实验获得了在170℃下,聚乳酸相对分子质量与链转移剂用量的定量关系,并用GPC、IR、1H-NMR、DSC等对聚合物的结构和性质进行了表征.     

星形聚乙二醇-聚乳酸嵌段共聚物的合成与表征

以不同臂数和分子量的星型聚乙二醇(sPEG)和L-丙交酯为原料,采用开环聚合法合成了以星型聚乙二醇为内部嵌段、聚L-乳酸为外部嵌段的多臂星形聚乙二醇-聚乳酸嵌段共聚物(sPEG-b-PLLA)。研究了sPEG的臂数、分子量及L-丙交酯/sPEG投料比等参数对产物结构与性能的影响。并分别用红外光谱(FT-IR)、核磁共振(1H-NMR)、凝胶渗透色谱(GPC)、差示扫描量热(DSC)对产物进行了表征,证实所合成的嵌段共聚物具有预期的结构。结果表明,sPEG-b-PLLA为结晶性聚合物,且表现出与PLLA相似的晶型,随着PLLA链段的增加,产物的结晶度也呈增大的趋势;与PLLA相比,sPEG-b-PLLA的接触角随着PEG链段的增多而增大,表明其亲水性明显改善。     

熔融缩聚合成聚L-乳酸的研究

以L-乳酸为原料,通过熔融缩聚法合成了聚乳酸(PLLA).考察了预聚条件、催化剂种类和用量、催化剂溶解程度、聚合温度及时间对聚乳酸分子量的影响.采用FTIR和1H-NMR分析聚合物结构,GPC测定分子量分布.研究表明,等摩尔量的氯化亚锡(SnCl2)和对甲苯磺酸(TSA)组成的复合催化剂效果最好,SnCl2的用量为预聚物(OLLA)的0.4%为宜;预聚过程和催化剂在OLLA中的充分溶解对提高聚合物分子量具有重要意义;合适的聚合温度约为165 ℃;在发生爬杆现象前,随反应时间的增加,聚乳酸分子量增加.在优化的工艺条件下,可以在较短时间(8 h)内获得分子量为65000左右的聚乳酸.     

原子转移自由基聚合制备PMMA/POSS杂化材料

以八(γ-氯丙基)倍半硅氧烷(OCP-POSS)为引发剂,通过原子转移自由基聚合(ATRP)制备了PMMA/OCP-POSS有机/无机杂化材料.采用GPC、DSC和TGA对杂化材料的结构与性能进行了表征.结果表明,在DMF、异丙醇、甲苯等3种不同溶剂中均可合成分子量分布较窄的PMMA杂化材料.以DMF为溶剂,所得PMMA/OCP-POSS杂化材料的分子量分布系数可达到1.18.与分子量相当的线形PMMA相比,含OCP-POSS的PMMA杂化材料具有更高的玻璃化转变温度和热稳定性.     

聚芳酰胺酰亚胺的合成与性能

以合成的高纯度偏苯三酸酐酰氯(TMAC)和4,4′-二氨基二苯醚为原料,N,N-二甲基乙酰胺为溶剂,制备聚酰胺酸预聚体,再用醋酐和三乙胺将其亚胺化得到聚酰胺酰亚胺(PAI),考察了聚合反应条件对分子量的影响,用FT-IR1、H-NMR表征了PAI的结构,并采用热失重(TGA)和差动扫描量热分析仪(DSC)对PAI进行热性能研究。     

POSS为核的高臂数星型杂化聚乳酸的合成

首先合成了含有8个羟基、结构极为对称的八聚[2-(2-羟基乙氧基)二甲基硅氧基]倍半硅氧烷,再以其为核引发D,L-丙交酯发生开环聚合,制备了含有八臂聚乳酸的星型有机-无机杂化POSS-PDLLA材料,通过FTIR、1H-NMR、GPC、DSC和TGA等手段对八羟基倍半硅氧烷和POSS-PDLLA杂化材料的化学结构和性能等进行了表征。结果表明,成功合成了单分散性的八羟基倍半硅氧烷,而POSS-PDLLA杂化聚合物分子量分布极窄(小于1.1)、玻璃化转变温度为43.6℃、热稳定性良好,具有与线性聚乳酸截然不同的特性。     

超临界CO2中聚乳酸的合成及表征

以辛酸亚锡为催化剂用超临界二氧化碳作溶剂成功地实现了L-丙交酯的开环聚合,聚合产物用FT-IR、^1H-NMR、^13C-NMR、DSC和GPC进行了分析表征,结果表明：超临界二氧化碳流体中左旋丙交酯开环聚合不是离子型聚合．可能是配位一插入聚合。所合成的聚乳酸具有很高的光学活性;所得聚合物无论分子量大小,都具有熔点和中等结晶度,且随分子量的增大而升高。     

L-丙交酯和D,L-丙交酯混合制备PLA工艺探讨

以辛酸亚锡为催化剂,采用开环聚合法,对L-丙交酯和D,L-丙交酯混合制备PLA工艺进行探讨,分别考察了D,L-丙交酯含量、催化剂用量、聚合时间、聚合温度和体系真空度对PLA粘均分子量的影响。经过GPC测试,所得PLA的质均分子量达到1.15×105,并采用红外光谱仪和差热-热重分析仪对PLA进行了结构和热性能表征。     

微波辐射D,L-丙交酯开环聚合制备聚乳酸

为得到聚乳酸的最佳制备工艺,利用微波辐射技术实现D,L-丙交酯开环聚合制备聚乳酸,实验考查了催化剂种类和用量,微波辐照功率和时间等工艺参数对产物分子量的影响,以及反应过程中体系温度的变化.研究表明,以连续微波炉作为反应器,催化剂Sn(Oct)2用量为丙交酯单体用量的0.56%(质量分数),在功率为90 W的连续微波辐射下反应10 m in,可获得粘均分子量(Mη)为15.92×104的聚乳酸(PDLLA).与家用微波炉相比,采用连续微波炉反应器,可在较短的反应时间内获得较高产率的聚乳酸产物.     

Fabrication of hydrophilic paclitaxel-loaded PLA-PEG-PLA microparticles via SEDS process

In this work, chemically bonded poly(D, L-lactide)-polyethylene glycol-poly(D, L-lactide) (PLA-PEG-PLA) triblock copolymers with various PEG contents and PLA homopolymer were synthesized via melt polymerization, and were confirmed by FTIR and ¹H-NMR results. The molecular weight and polydispersity of the synthesized PLA and PLA-PEG-PLA copolymers were investigated by gel permeation chromatography. Hydrophilicity of the copolymers was identified by contact angle measurement. PLA-PEG-PLA and PLA microparticles loaded with and without PTX were then produced via solution enhanced dispersion by supercritical CO₂ (SEDS) process. The effect of the PEG content on the particle size distribution, morphology, drug load, and encapsulation efficiency of the fabricated microparticles was also studied. Results indicate that PLA and PLA-PEG-PLA microparticles all exhibit sphere-like shape with smooth surface, when PEG content is relatively low. The produced microparticles have narrow particle size distributions and small particle sizes. The drug load and encapsulation efficiency of the produced microparticles decreases with higher PEG content in the copolymer matrix. Moreover, high hydrophilicity is found when PEG is chemically attached to originally hydrophobic PLA, providing the produced drug-loaded microparticles with high hydrophilicity, biocompatibility, and prolonged circulation time, which are considered of vital importance for vessel-circulating drug delivery system.     

Non-conventional injection molding of poly(lactide) and poly(ε-caprolactone) intended for orthopedic applications

Biodegradable polymers such as poly(lactide) (PLA) and poly(epsilon-caprolactone) (PCL) are increasingly used in biomedical applications as temporary implants. However, melt processing of these materials in particular of PLA is difficult due to the temperature sensitivity. Within this study, PLA and PCL were injection molded conventionally and by using the process shear controled orientation in injection molding (SCORIM) in order to investigate the effect of processing parameters on the physical properties of the moldings. Therefore, flexural testing, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), molecular weight (MW) and orientation measurements were performed. PLA showed high sensitivity to melt temperature. In the case of amorphous poly(DL-lactide), the molecular weight and subsequently the ductility is substantially reduced by processing at higher melt temperatures. In the case of crystallizable poly(L-lactide), higher melt temperatures and shear induced by the SCORIM process resulted in enhanced crystallinity, which compromised the mechanical properties. Generally, SCORIM processing improved the mechanical properties, in particular the ductility, by orientating the molecular structure. PCL was shown to be less sensitive to shear and temperature than PLA. Stress at yield and stiffness are more improved by SCORIM processing. However, the processing temperature in combination with the grade used proved to be influential for the mechanical properties of resulting moldings.     

聚乙二醇对淀粉原位熔融接枝聚乳酸的影响

研究了在聚乙二醇(PEG)存在下,淀粉与丙交酯的原位熔融接枝反应。较系统地考察了PEG的加入量及分子量的变化对淀粉一聚乳酸原位熔融接枝反应的影响。结果表明,当有PEG存在时,丙交酯可以有效地接枝到淀粉链上,得到淀粉一聚乳酸接枝共聚物。PEG对淀粉的增塑效果是影响淀粉与丙交酯熔融接枝反应至关重要的因素。     

An Investigation of the Synthesis of Poly(D,L-Lactic Acid) and Preparation of Microspheres Containing Indomethacin

Abstract

Seven batches of poly(D, L-lactic acid) (PLA) were prepared from D, L-lactic acid using tetraphenyltin or zinc acetate as a catalyst. The samples of PLA were characterized by terminal group analysis, gel permeation chromatography, infrared analysis, and differential scanning calorimetry. Polymerization conditions such as the time of reaction and the type of catalyst affected the molecular weight of PLA. Microspheres containing indomethacin were prepared by the oil/water (o/w) solvent evaporation technique using different formulations and process variables. The in vitro release of indornethacin in phosphate buffer was found to be dependent on the molecular weight of PLA and also on the type and amount of adjuvants used. The batch of microspheres containing 5% cholesterol released the drug at a slow controlled rate (29%, 65%. and 85% in 1, 7, and 24 hr, respectively). The results of F test for the microspheres revealed that there is no significant direrence between the Higuchi model and the power law equation. The drug was released by a dimsion mechanism from the microspheres.     

An Investigation of the Synthesis of Poly(D, L-Lactic Acid) and Preparation of Microspheres Containing Indomethacin

Seven batches of poly(D, L-lactic acid) (PLA) were prepared from D, L-lactic acid using tetraphenyltin or zinc acetate as a catalyst. The samples of PLA were characterized by terminal group analysis, gel permeation chromatography, infrared analysis, and differential scanning calorimetry. Polymerization conditions such as the time of reaction and the type of catalyst affected the molecular weight of PLA. Microspheres containing indomethacin were prepared by the oil/water (o/w) solvent evaporation technique using different formulations and process variables. The in vitro release of indornethacin in phosphate buffer was found to be dependent on the molecular weight of PLA and also on the type and amount of adjuvants used. The batch of microspheres containing 5% cholesterol released the drug at a slow controlled rate (29%, 65%. and 85% in 1, 7, and 24 hr, respectively). The results of F test for the microspheres revealed that there is no significant direrence between the Higuchi model and the power law equation. The drug was released by a dimsion mechanism from the microspheres.     

聚乳酸的合成研究

聚乳酸是一种具有良好生物相容性、可降解的高分子材料,被广泛应用于医用领域,受到越来越多的关注。聚乳酸的合成主要有两种方法：乳酸直接缩聚和丙交酯的开环聚合。文中综述了近年来聚乳酸合成研究的最新进展,讨论了直接合成时的反应条件对聚乳酸分子量的影响,似及不同催化剂对丙交酯开环聚合的影响,介绍了聚乳酸聚合的一种高效方法——反应挤出法,并展望了聚乳酸合成研究的前景。     

聚乳酸大分子引发剂的一步法合成

在异辛酸亚锡的催化下,以三溴乙醇作为引发剂,通过L-丙交酯一步开环聚合合成了端基含有溴原子的聚乳酸大分子引发剂PLLA-Br,为进一步通过ATRP反应制备聚乳酸嵌段共聚物奠定基础。利用GPc考察了PLLA-Br的数均分子量及分子量分布与反应时间的关系。FT-IR、~1H-NMR、DSC和TG等结果表明,PLLA-Br链端含有溴原子,属结晶聚合物,其结晶温度在104℃,熔融温度约为180℃,热分解温度高于200℃。     

木纤维-聚乳酸复合材料性能与聚乳酸性能的相关性

用高速混合-平板热压法制备了70%木纤维含量的木纤维-聚乳酸(WF-PLA)复合材料,研究了不同聚乳酸(PLA)对WF-PLA复合材料的耐水性、弯曲强度和弯曲模量、PLA分子量及热性能的影响。结果表明,PLA与木纤维复合后,弯曲模量明显增加,复合材料中PLA分子量和熔融温度明显下降;PLA性能对WF-PLA复合材料性能影响显著,WF-PLA复合材料中PLA分子量随PLA原料分子量下降而下降,高分子量PLA制备的WF-PLA复合材料耐水性更好,弯曲强度和弯曲模量更高;在PLA改性时,应避免引起PLA分子量下降。