熔融/固相缩聚法合成聚乙醇酸及其性能表征

采用熔融/固相缩聚法合成了聚乙醇酸(PGA)可降解高分子材料,其基本反应步骤为:以乙醇酸为原料,先在190℃熔融状态下将乙醇酸脱水制成分子量为2万左右的低聚物,然后将制得的低聚物在190℃下进行固相缩聚以进一步提高分子量,所制备的PGA产物通过IR、DSC、XRD等手段进行表征。重点考察了不同催化剂,催化剂用量、是否熔融、反应温度、反应时间等因素对固相缩聚的影响,并得出熔融/固相缩聚法合成高分子量的聚乙醇酸的较佳工艺条件:反应温度190℃,二水合醋酸锌与等摩尔量的对甲苯磺酸作为催化剂(质量分数为0.4%),熔融缩聚2h后制得低聚物,然后在190℃下进行固相缩聚,40h后熔融一次,产品粉碎后继续固相缩聚60小时,PGA的重均分子量可达74000左右。     

聚磷酸酯医用材料

聚磷酸酯是一种生物相容性好、结构较易进行修饰和功能化的生物降解高分子，可以应用于药物缓释材料、组织工程材料、动物体内显影剂等医用领域。本文论述了近年来的聚磷酸酯医用材料的研究进展，尤其是作为药物缓释材料的合成与应用情况。随着合成研究的深入，聚磷酸酯在医用材料方面的应用将更加引人注目。     

乙醇酸和DL—乳酸交替共聚物的合成和表征

乙醇酸和ＤＬ－乳酸交替共聚物具有不同于其无规共聚物的理化性能和生物降解性。以ＤＬ－３－甲基－１２，４－恶烷－２，５－二酮为单全，通过在辛酸亚锡引发下的本体开环聚合，合成了该交替共聚物，并进行了结构表征。     

生物降解聚合物的研究和产业化进展及展望

结合作者等近十年来在生物降解聚合物领域的研究和产业化工作,本文概述了聚乳酸、聚氨基酸、聚对二氧六环酮及其它生物降解聚合物的合成进展,综述了可生物降解温度敏感水凝胶、形状记忆高分子材料的研究概况,阐述了可生物降解聚合物在生物活性大分子控释体系、超细纤维组织工程支架上的应用研究,介绍了可生物降解聚合物在食品包装、纺织和汽车电子等方面的应用,总结了可生物降解聚合物、医疗器械、药物制剂和组织工程等领域产业化近况.最后展望了生物降解聚合物的研究、应用和产业化前景.     

乙醇酸和DL─乳酸交替共聚物的合成和表征

乙醇酸和ＤＬ－乳酸交替共聚物具有不同于其无规共聚物的理化性能和生物降解性。以ＤＬ－３－甲基－１，４－二烷－２，５－二酮为单体，通过在辛酸亚锡引发下的本体开环聚合，合成了该交替共聚物，并进行了结构表征。     

聚羟基乙酸及其共聚物

对聚羟基乙酸及其共聚物的合成方法 ,生物降解性 ,生物相容性 ,力学性能 ,共聚改性等方面的研究进展做了综述 ,并讨论了聚羟基乙酸类材料的医学应用现状及前景     

生物医用类聚天冬氨酸衍生物的研究进展

聚氨基酸类高分子材料因其良好的生物相容性、生物可吸收性及化学结构匹配性,在生物医用高分子领域有着无法比拟的优点和广泛的应用前景。特别是聚天冬氨酸,具有良好的生物相容性、生物降解性和可吸收性,合成方法简单,成本较低,易于功能化修饰等诸多优点。且在体内能够被逐渐吸收代谢,其代谢产物对人体无毒,不会对周围组织、肝肾、血红细胞等产生毒副作用。因此聚天冬氨酸及其衍生物,被广泛用于药物载体、组织工程等生物医药领域相关材料的制备研究。本文综述了近几年来聚天冬氨酸在生物医用高分子领域内的应用,重点介绍了聚(α,β-L-天冬氨酸)衍生物的设计合成及其生物医学性能。     

生物降解高分子材料聚丁二酸丁二醇酯的改性研究进展

生物降解高分子材料被公认为是聚丙烯、聚乙烯等传统高分子材料造成"白色污染"的问题的重要解决方法之一。聚丁二酸丁二醇酯是重要的可生物降解的脂肪族聚酯之一,因与传统的聚丙烯、聚乙烯高分子材料具有相近的物理和力学性能,从而引起科学与工业界的广泛重视。然而,与大多数脂肪族聚酯一样,PBS材料也存在着加工、种类少、性能应用上的缺点。因此,对其通过改性拓宽用途范围的研究报道也随之增多。本文从化学、物理等改性的手段方法为着眼点,分类阐述了近些年来生物降解高分子材料聚丁二酸丁二醇酯改性研究现状与进展。     

聚羧基乙酸及其共聚物

对聚羧基乙酸及其共聚物的合成方法，生物降解性，生物相容性，力学性能，共聚改性等方面的研究进展做了综述，并讨论了聚羟基乙酸类材料的医学应用现状及前景。     

利用一氧化碳合成高分子材料

介绍一氧化碳分别与烯烃、甲醛、胺类等化俣物共聚制备聚酮、聚酯、聚胺等，与一氧化碳被氢气还原制备聚合甲烯的化学反应原理和应用实例，以及开发利用一氧化碳合成高分子材料的动向和发展前景。     

Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society

In recent years the littering of plastics and the problems related to their persistence in the environment have become a major focus in both research and the news. Biodegradable polymers like poly(lactic acid) are seen as a suitable alternative to commodity plastics. However, poly(lactic acid) is basically non‐degradable in seawater. Similarly, the degradation rate of other biodegradable polymers also crucially depends on the environments they end up in, such as soil or marine water, or when used in biomedical devices. In this Minireview, we show that biodegradation tests carried out in artificial environments lack transferability to real conditions and, therefore, highlight the necessity of environmentally authentic and relevant field‐testing conditions. In addition, we focus on ecotoxicological implications of biodegradable polymers. We also consider the social aspects and ask how biodegradable polymers influence consumer behavior and municipal waste management. Taken together, this study is intended as a contribution towards evaluating the potential of biodegradable polymers as alternative materials to commodity plastics.     

Biodegradable polyesters for medical and ecological applications

Numerous biodegradable polymers have been developed in the last two decades. In terms of application, biodegradable polymers are classified into three groups: medical, ecological, and dual application, while in terms of origin they are divided into two groups: natural and synthetic. This review article will outline classification, requirements, applications, physical properties, biodegradability, and degradation mechanisms of representative biodegradable polymers that have already been commercialized or are under investigation. Among the biodegradable polymers, recent developments of aliphatic polyesters, especially polylactides and poly(lactic acid)s, will be mainly described in the last part.     

New Unsaturated Biodegradable Poly(ester amide)s Composed of Fumaric Acid,L-leucine and α,ω-Alkylene Diols

The synthesis of α-amino acid L-leucine (Leu) based high-molecular-weight and biodegradable unsaturated poly(ester-amide)s (PEAs) was reported. Amino acid L-phenylalanine (Phe) was used to synthesize some copolymers for a comparative study. The syntheses of three types of new unsaturated PEA polymers were explored – (i) Unsaturated PEA homopolymers (UPEAs) composed of fumaric acid, aliphatic diol and one alpha-amino acid: L-Leu or L-Phe; (ii) L-Leu-based unsaturated-saturated copolymers (USPEAs) composed of aliphatic diol, fumaric and saturated fatty diacid, and (iii) L-Leu- and L-Phe-based copolymers (co-UPEAs) composed of 100% fumaric acid, aliphatic diol and combinations of both amino acids. Many of the targeted unsaturated polymers were soluble in common organic solvents and showed good film-forming property. The unsaturated PEA polymers were further chemically modified into functional derivatives and subjected to thermal and photochemical transformations (curing) that substantially expand material properties and, hence, the scopes of potential applications as absorbable surgical devices and drug carriers.     

Fracture evaluation of plasticized polylactic acid / poly (3-HYDROXYBUTYRATE) blends for commodities replacement in packaging applications

Nowadays, scientific and technological efforts are being carried out to diminish serious ecological problems caused by indiscriminate use of non-biocompostable polymers in the packaging industry. In this sense, novel biodegradable blends of different composition based on poly(lactic acid) (PLA), poly(3-hydroxybutyrate) (PHB) and tributyrin (TB) are developed and here proposed as an eco-friendly alternative. Materials are characterized by fracture experiments under quasi-static and biaxial impact loading. Fracture behavior is analyzed together with thermal, tensile and water permeation properties to evaluate their potential in-service performance. TB_PLA/PHB blends with 15 wt% TB exhibit better permeation and fracture toughness than currently used bio-based polymers, being in the range of polyethylene properties. Results highlight the potential of these new blends broadening the current application field of PLA.     

Water-soluble biodegradable polymers: Synthetic or natural-based raw materials?

In this paper, we review some of the significant synthesis approaches that we and others have evaluated for producing commercially viable water-soluble biodegradable polymers. The goals set for these polymers, cost/performance equivalent with current non-biodegradable polymers and complete biodegradation or a high degree of certainty that they are free from potential adverse environmental impact, are realistic but very difficult to achieve. Hence, we believe that few new polymers are emerging or are likely to emerge in the near future because of the radical directional changes needed in the synthesis and environmental testing procedures for water-soluble biodegradable polymers. We consider polymers with structures and compositions that mimic nature most likely to eventually be successful in the market place regardless of raw material origin, provided that cost/performance comparable with current commercial polymers can be achieved. Poly(aspartic acid), recently developed, may be considered as a prototype of things to come.     

Molecular Design of Synthetic Biodegradable Polymers as Cell Scaffold Materials

Poly(lactic acid) and its copolymers are regarded as the most useful biomaterials. The good biocompatibility, biodegradability and mechanical properties of them make the synthetic biodegradable polymers have primary application to tissue engineering. The advantages and disadvantages of the synthetic biodegradable polymers as cell scaffold materials are evaluated, This article reviews the modification of polylactide-family aliphatic polymers to improve the cell affinity when the polymers are used as cell scaffolds. We have developed four main approaches: to modify polyester cell scaffolds in combination of plasma treating and collagencoating; to introduce hydrophilic segments into aliphatic polyester backbones; to introduce pendant functional groups into polyester chains ; to modify polyester with dextran. The results of the cell cultures prove that the approaches mentioned above have improved the cell affinity of the polyesters and have modulated cell function such as adhesion, proliferation and migration.     

Synthesis and characterization of amphiphilic block copolymer of polyphosphoester and poly(L‐lactic acid)

Aliphatic polyesters and polyphosphoesters (PPEs) have received much interest in medical applications due to their favorable biocompatibility and biodegradability. In this work, novel amphiphilic triblock copolymers of PPE and poly(L ‐lactic acid) (PLLA) with various compositions were synthesized and characterized. The blocky structure was confirmed by GPC analyses. These triblock copolymers formed micelles composed of hydrophobic PLLA core and hydrophilic PPE shell in aqueous solution. Critical micellization concentrations of these triblock copolymers were related to the polymer compositions. Incubation of micelles at neutral pH followed by GPC analyses revealed that these polymer micelles were hydrolysized and resulted in decreased molecular weights and small oligomers, whereas its degradation in basic and acid mediums was accelerated. MTT assay also demonstrated the biocompatibility against HEK293 cells. These biodegradable polymers are potential as drug carriers for biomedical application. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6425–6434, 2008     

Polyglycolic acid copolymers from one‐step cationic polymerization of formaldehyde,carbon monoxide,and epoxides derived from PEG

Biodegradable polyglycolic acid (PGA) is conventionally produced via the ring‐opening polymerization of glycolide, the cyclic dimer form of glycolic acid, in the presence of mostly tin‐based catalyst initiators which are rather known to be cytotoxic materials. Our previous studies revealed an alternative method for the synthesis of PGA from the perfectly alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) under BrØnsted acidic conditions. The poor physical properties of PGA (insolubility in many organic solvents, brown color, etc.) limit its use in other marketing applications in the industry. To improve on the physical properties of PGA, such as solubility and appearance, copolymerization of trioxane, CO, and a minor amount of epoxides derived from polyethylene glycol (PEG) were performed under the same reaction conditions for PGA synthesis (in DCM, at 800 psi CO pressure, with triflic acid catalyst, reaction duration of 72 hours). The results have shown that the addition of minor quantities of epoxide comonomers vastly improves the appearance of the obtained PGA copolymers and allows for the control of the polymeric properties, such as solubility and melting temperature.