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。     

生物降解材料聚乳酸合成的研究进展

介绍了聚乳酸的主要特点、合成方法及应用领域,重点阐述了丙交酯开环聚合催化剂的研究进展及催化机理,以及乳酸直接缩聚的合成工艺;讨论了各合成方法的优势特点,提出了合成中亟待解决的问题;并对其发展前景进行预测和展望。     

聚乳酸合成研究进展

针对直接法和二步法合成聚乳酸的共性,从单体纯度、催化剂选择到共沸脱水、微波辅助、超临界流体介质,以及到固相聚合、反应挤出、扩链等各个方面,对近年来聚乳酸合成研究的新进展进行了综述,指出各种新方法、新技术的复合应用是提高聚乳酸分子量、降低其成本的关键。     

聚乳酸的微波辐射合成方法研究

采用微波加热提供反应所需热量,以丙交酯为原料,辛酸亚锡的甲苯溶液为催化剂,进行丙交酯开环聚合反应,开展了聚乳酸的微波辐射合成工艺及相关基础研究。在最佳条件下(催化剂辛酸亚锡与单体的摩尔比为0.001,SiC作辅助加热介质,微波功率为450W,反应18min)合成了分子量为2.5×104的聚乳酸。     

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℃.     

聚乳酸的合成、结构及性能

乳酸经减压蒸馏制得单体丙交酯，再以氧化锌为催化剂聚合得到聚乳酸。单体及聚合物均由结构鉴定证实，对产物的分子量、力学性能及降解等重要性质作了研究。     

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。     

绿色高分子材料聚乳酸的制备工艺研究进展

可再生资源、可生物降解绿色高分子材料聚乳酸(PLA)应用前景广阔.从聚合设备、聚合条件以及聚合材质3个方面着重总结了丙交酯开环聚合工艺,产品中低分子杂质的脱除是高聚物生产工艺难点,分析了再沉淀、溶剂萃取、真空熔融及无催化反应等脱挥方法,重点推荐了Hitomi Ohara脱挥工艺流程.     

医用聚乳酸的合成及其管型材料性能的测定

本文以无毒的辛酸亚锡作催化剂,将丙交酯聚合成聚乳酸(PLA)。研究了在760～0.05mmHg范围内压力改变对PLA分子量的影响,并将PL制成内径为2mm的管型材料,经热稳定性、机械强度和降解性能等试验,结果都表明此管材可用作引导神经再生导管材料。     

溶剂热合成法制备聚乳酸及其性能

以丙交酯为原料,氯化亚锡为催化剂,通过热溶剂法在170℃反应12h开环聚合制得聚乳酸。采用乌氏黏度计,红外光谱(FT-IR),差示扫描量热(DSC)和凝胶渗透色谱(GPC)等对所得聚合物进行了分子量测定和结构性能表征,证实了溶剂热合成方法制备聚乳酸的可行性。同时研究了氯仿,丁酮和甲苯三种溶剂对最终合成产物结构及分子量的影响,并用GPC和DSC考察了受阻酚和亚磷酸酯类的抗氧化剂组合对聚乳酸分子量和熔融结晶行为的影响。     

生物可降解高分子增韧聚乳酸的研究进展

聚乳酸(PLA)是一种新型的生物基可再生生物降解材料,因具有高机械强度、易加工性、高熔点、可生物降解性和生物相容性等优点而得到广泛的关注。然而,其固有的脆性,即低断裂伸长率和断裂强度严重限制了它在实际中的应用,但也因此吸引了更广泛的深入研究。本文综述了以生物可降解高分子增韧聚乳酸的研究进展,重点阐述了生物基聚酯,生物基弹性体,植物基生物高分子,天然橡胶和植物油以及生物大分子增韧聚乳酸的最新研究发展概况,同时提出了在经过改善韧性之后,聚乳酸存在的冲击韧性弱以及低结晶速率和低热转变温度等问题,并分析了未来的发展方向和需要关注的主题。     

希夫碱钛配合物催化D,L-丙交酯本体开环合成聚乳酸

合成了一种新型双核希夫碱钛配合物,并将此作为催化剂用于D,L型丙交酯本体开环聚合,采用FT-IR、NMR、GPC对合成产物进行表征,研究结果表明该配合物具有催化丙交酯开环较高的催化活性和分子量可控性（PDI=1.09～1.24）。同时进一步研究了该催化剂用量,聚合温度及聚合时间对聚合反应的影响,发现在单体与催化剂摩尔比为2600,聚合时间为16h,聚合温度为160℃时,可得到数均分子质量Mn=9.058×104,PDI=1.16的聚乳酸材料。     

Biodegradable polymers: A review about biodegradation and its implications and applications

Plastic waste pollution is a global environmental problem that could be solved by biodegradable materials. In addition, its biodegradability has been important for medical applications. In this way, the biodegradability performance has been investigated for different materials under diversified environmental conditions. In this context, this review shows the main up-to-date biodegradable polymers (from renewable sources and fossil-based), their structure and properties, and their biodegradability characteristics. Also, this review shows the effect of polymer properties and environmental conditions on biodegradability, methods of biodegradability and toxicity determination, modification processes to enhance biodegradability, and main applications of biodegradable polymers for agriculture, medical, and packaging. Finally, this review presents a discussion of the implications of biodegradation on the environment, the current context, and future perspectives of plastic biodegradation.     

高分子量聚乙交酯的合成及表征

以辛酸亚锡为催化剂,十二醇为分子量调节剂,经乙交酯开环聚合合成了高相对分子量的聚乙交酯(PGA)。研究不同催化剂含量、调节剂含量和反应时间对合成反应的影响。通过改变催化剂含量,合成特性黏数达3.848 dL/g的PGA;固定催化剂含量,通过改变调节剂含量,得到特性黏数在2.278 dL/g～3.218 dL/g范围内可调的PGA。用红外光谱,核磁共振,X射线衍射(XRD),差示扫描量热(DSC)和热重分析(TGA)表征其结构和性能。结果表明,PGA是一种半结晶聚合物,结晶度达48.72%,其熔融温度在222℃～224℃之间,具有良好的热学性能。     

聚乳酸基聚苯胺柔性可降解超级电容器的制备与性能

随着全球经济的快速发展、化石燃料的枯竭及环境污染等问题的加剧,社会对新型的电化学储能技术的需求日趋迫切.近年来,超级电容器由于其高的功率密度、长的循环寿命、宽的工作温度、优异的稳定性等优势引起了广泛关注.但由于传统的电容器器件大而重、制造过程繁复、且大多数不能够降解,已经不能满足社会的可持续发展需要,因此制备一种新型柔...     

ATRP-based synthesis and characterization of light-responsive coatings for transdermal delivery systems

Abstract

The grafting of poly(hydroxyethylmethacrylate) on polymeric porous membranes via atom transfer radical polymerization (ATRP) and subsequent modification with a photo-responsive spiropyran derivative is described. This method leads to photo-responsive membranes with desirable properties such as light-controlled permeability changes, exceptional photo-stability and repeatability of the photo-responsive switching. Conventional track etched polyester membranes were first treated with plasma polymer coating introducing anchoring groups, which allowed the attachment of ATRP-initiator molecules on the membrane surface. Surface initiated ARGET–ATRP of hydroxyethylmethacrylate (where ARGET stands for activator regenerated by electron transfer) leads to a membrane covered with a polymer layer, whereas the controlled polymerization procedure allows good control over the thickness of the polymer layer in respect to the polymerization conditions. Therefore, the final permeability of the membranes could be tailored by choice of pore diameter of the initial membranes, applied monomer concentration or polymerization time. Moreover a remarkable switch in permeability (more than 1000%) upon irradiation with UV-light could be achieved. These properties enable possible applications in the field of transdermal drug delivery, filtration, or sensing.     

Pharmaceutical applications of hot-melt extrusion: Part II

The advent of high through-put screening in the drug discovery process has resulted in compounds with high lipophilicity and poor solubility. Increasing the solubility of such compounds poses a major challenge to formulation scientists. Various approaches have been adopted to address this including preparation of solid dispersions and solid solutions. Hot-melt extrusion is an efficient technology for producing solid molecular dispersions with considerable advantages over solvent-based processes such as spray drying and co-precipitation. Hot-melt extrusion has been demonstrated to provide sustained, modified, and targeted drug delivery. Improvements in bioavailability utilizing the hot-melt extrusion technique demonstrate the value of the technology as a potential drug delivery processing tool. The interest in hot-melt extrusion technology for pharmaceutical applications is evident from the increasing number of patents and publications in the scientific literature. Part II of this article reviews the myriad of hot-melt extrusion applications for pharmaceutical dosage forms including granules, pellets, tablets, implants, transmucosal, and transdermal systems.     

ATRP-based synthesis and characterization of light-responsive coatings for transdermal delivery systems

The grafting of poly(hydroxyethylmethacrylate) on polymeric porous membranes via atom transfer radical polymerization (ATRP) and subsequent modification with a photo-responsive spiropyran derivative is described. This method leads to photo-responsive membranes with desirable properties such as light-controlled permeability changes, exceptional photo-stability and repeatability of the photo-responsive switching. Conventional track etched polyester membranes were first treated with plasma polymer coating introducing anchoring groups, which allowed the attachment of ATRP-initiator molecules on the membrane surface. Surface initiated ARGET–ATRP of hydroxyethylmethacrylate (where ARGET stands for activator regenerated by electron transfer) leads to a membrane covered with a polymer layer, whereas the controlled polymerization procedure allows good control over the thickness of the polymer layer in respect to the polymerization conditions. Therefore, the final permeability of the membranes could be tailored by choice of pore diameter of the initial membranes, applied monomer concentration or polymerization time. Moreover a remarkable switch in permeability (more than 1000%) upon irradiation with UV-light could be achieved. These properties enable possible applications in the field of transdermal drug delivery, filtration, or sensing.