环氧乙烷环氧丙烷共聚醚的研究进展

综述了环氧乙烷环氧丙烷共聚醚的聚合机理聚合工艺及其应用.环氧乙烷环氧丙烷共聚醚的聚合按其催化剂体系的机理可以分为阴离子聚合、阳离子聚合和配位聚合三类,其中阳离子聚合应用较少.在环氧乙烷和环氧丙烷开环聚合生成共聚醚的反应中,不同的反应工艺条件对生成的聚醚有着很大的影响.同样比例的环氧乙烷和环氧丙烷,因聚合反应器设计、反应器种类、起使剂种类催化剂种类与用量温度加料方式端基结构等的不同,所合成的共聚醚会产生不同的结构和性能.环氧乙烷环氧丙烷共聚形成的聚醚可以分为嵌段共聚醚和无规共聚醚两类.其中,嵌段共聚醚可以分为EPE和PEP两类.     

胆甾型侧链液晶共聚物的研究

合成并表征了两个胆甾型液晶烯类单位以及它们分别与辛烯－１，二氧化硫进行自由基共聚合得到的一系列不同组成的胆甾型侧链液晶三元共聚砜。研究结果表明：该共聚砜的两个液晶热转变温度均随其中辛烯－１单体单元组份含量的增加而降低。     

AN/St悬浮共聚体系中AN在水/油两相间分配及其对共聚物组成的影响

研究了丙烯腈/苯乙烯(AN/St)悬浮共聚体系中AN在水/油两相间的分配及其对AN/St共聚物组成的影响.结果表明,AN分配于水/油两相间,使油相AN的含量低于相同单体配料比的本体聚合,导致生成的AN/St共聚物组成偏离本体共聚.为了准确预测进而控制AN/St悬浮共聚物的组成,提出了在考虑AN相分配的基础上计算AN/St悬浮共聚物组成的模型.计算结果与实验值一致,计算中用到的油相实际竞聚率与本体聚合相同,但该悬浮聚合的表观竞聚率随水/油比的变化而发生较大改变.     

庚烯-1单体单元对胆甾型侧链液晶共聚砜热转变温度的调节

合成并用红外光谱法、核磁共振法和高效凝胶渗透色谱法表征了胆甾（烷）醇十一碳烯酸酯分别与庚烯 １、二氧化硫进行自由基共聚合得到的一系列不同组成的三元胆甾型侧链液晶共聚砜，用温控式偏振光显微镜观测了产物的液晶性能．结果表明：随庚烯 １单体单元组份含量的增加，该三元共聚砜的液晶相转变温度均降低，采用庚烯 １单体参与共聚的方法可以有效地调节胆甾型侧链液晶共聚砜的热转变温度．     

理想共聚体系共聚物组成方程的推导

理想共聚体系共聚物组成方程的推导彭宇行（中国科学院成都有机化学研究所，６１００４１）理想共聚是连锁聚合反应（自由基聚合、阳离子聚合和阴离子聚合）中的一类特殊共聚体系。在理想共聚中由不同单体生成的链增长活性中心对各共聚单体具有相同的反应活性，使得共聚物...     

不伴随解聚的二元共聚反应的计算机模拟

用计算机模拟化学反应是一项饶有兴趣的研究课题。本文主要讨论不伴随解聚的二元共聚反应的计算机模拟问题。通过模拟,希望能获得如下两方面信息:(1)给出任意的某一原料单体组成下所对应的共聚体的组成。(2)给出共聚体中单体单元的序列分布。我们知道,高分子具有多分散性的特点,对共聚体而言,除分子量的多分散性以外,还须研究共聚物组成     

丙烯腈/衣糠酸共聚行为的Monte Carlo模拟

建立了针对丙烯腈/衣糠酸共聚反应的Monte Carlo模拟算法,首先在不同pH值单体竞聚率条件下计算了共聚组成随单体投料比的变化,由实验结果验证了该Monte Carlo模型的准确性。在此基础上,对丙烯腈共聚物链结构的变化规律和影响因素进行了理论分析,指出传统一次性进料工艺中存在共聚物组成和序列结构均匀性差的问题,进而根据模拟计算结果提出调控共聚物序列结构均匀性的可行性方案。结果表明,通过在聚合不同阶段分时按比例补加活泼单体衣糠酸(ITA),可以对聚合产物的瞬时组成和序列结构起到有效的平均化效果,从而改善共聚组成和序列结构的均匀化程度,这种链结构的改进将有利于最终碳纤维性能的提高。     

用均相的稀土催化剂进行丁二烯-异戊二烯本体共聚合的研究

本工作用均相的稀土催化体系Nd(naph)_3-Al(i-Bu)_2H-CH_3SiHCl_2进行了丁二烯和异成二烯的本体共聚合,研究了聚合规律和产物的结构性能.结果表明,在适当的催化剂组分比条件下,该催化体系具有较高的催化活性,用DSC测定了共聚物的玻璃化转变温度,~1H-NMR和IR分别测定了共聚物的组成和微观结构,证明共聚物的组成主要决定于单体原料的配料比,共聚物中两种单体单元都具有高顺式结构,生胶和硫化胶的性能测定表明,在丁二烯和异戊二烯两种单体的配料比为30比70时,得到的共聚胶的综合性能较好.     

醋酸乙烯酯-丙烯酸丁酯乳液聚合成核机理

本工作研究了醋酸乙烯酯(VA)和丙烯酸丁酯(BA)乳液共聚合.通过对不同共聚单体配比下共聚合时胶乳粒径及胶粒数密度随转化率变化的分析,对VA/BA乳液共聚合成核及粒增长机理进行了探讨,指出水相成核是高VA含量时胶粒数密度较大的主要原因并解释了胶粒数密度及胶乳粒径与单体转化率的关系,同时也讨论了该共聚体系一步法聚合时反应机理与胶粒形态的关系.     

丙烯聚合用TiCl_4/MgCl_2催化剂的研究——聚合温度和烷基铝的影响

研究了不同助催化剂和不同聚合温度对催化剂TiCl4/MgCl2/9,9-双(甲氧基甲基)芴(BMMF)丙烯聚合性能的影响.研究结果发现该催化剂在高温(100℃)聚合时,采用还原能力和络合能力较弱的烷基铝(Hex3Al)为助催化剂可以得到高的立构选择性(97%)和高活性.100℃聚合时不同的助催化剂对催化剂得到的聚丙烯结构有重要影响.助催化剂为Me3Al聚合得到的中等等规聚丙烯含量比其他烷基铝高.助催化剂为Et3Al聚合得到聚丙烯链结构中含有少量乙烯共聚单元;而助催化剂为Me3Al,iBu3Al和Hex3Al聚合得到聚丙烯链结构中没有发现共聚单元.     

聚羧基脂肪酸酯细菌合成的生长环境依赖性

聚羟基脂肪酸酯（Ｐｏｌｙｈｙｄｒｏｘｙａｌｋａｎｏａｔｅ,ＰＨＡ）是一类由许多细菌合成的、结构多变的能量和碳源的储藏物质,为了得到能合成新型ＰＨＡ的菌种,或得到能在便宜简单碳源上合成ＰＨＡ的菌种,以我们实验室开发的傅立叶红外（ＦＴ－ＩＲ）细胞无损检测技术和常规气相色谱（ＧＣ）法对全国各地的采集的不同样品中分离的菌种进行了筛选,往往在不同的地理环境中,筛选出的菌株所合成的ＰＨＡ的单体组成不同,有以含四个或五个碳原子的短链单体ＰＨＡ（Ｓｈｏｒｔ－ｃｈａｉｎ－ｌｅｎｇｔｈＰＨＡ,ｓｃｌＰＨＡ）为主,有的以含六个到十六个碳原子的中长链单体ＰＨＡ（Ｍｅｄｉｕｍ－ｃｈａｉｎ－ｌｅｎｇｔｈＰＨＡ,ｍｃｌ ＰＨＡ）为主,在我们以六种底物为碳源培养的３７１株形态不一的菌株中,有４０％的菌可以合成ＰＨＡ,而其中许多可以同时合成ＰＨ     

聚羟基脂肪酸酯细菌合成的生长环境依赖性

聚羟基脂肪酸酯 (Polyhydroxyalkanoate,PHA)是一类由许多细菌合成的、结构多变的能量和碳源的储藏物质 .为了得到能合成新型PHA的菌种 ,或得到能在便宜简单碳源上合成PHA的菌种 ,以我们实验室开发的傅立叶红外 (FT IR)细胞无损检测技术和常规气相色谱 (GC)法对全国各地的采集的不同样品中分离的菌种进行了筛选 .往往在不同的地理环境中 ,筛选出的菌株所合成的PHA的单体组成不同 ,有的以含四个或五个碳原子的短链单体PHA(Short chain lengthPHA ,sclPHA)为主 ,有的以含六个到十六个碳原子的中长链单体PHA(Medium chain lengthPHA ,mclPHA)为主 .在我们以六种底物为碳源培养的 371株形态不一的菌株中 ,有 40 %的菌可以合成PHA ,而其中许多可以同时合成PHB与中长链PHA共混的聚合物 .本研究为进行PHA研究的高分子同行提供了寻找能合成PHA的微生物菌种的依据     

Effect of C∶N molar ratio on monomer composition of polyhdroxyalk anoates produced by Pseudomonas mendocina 0806 and Pseudomonas pseudoalkaligenus YS1

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by bacteria. In this study, the effect of C∶N molar ratio on the monomer composition of PHAs was investigated, including medium chain length PHA produced by Pseudomonas mendocina 0806 and PHA blends consisting of monomers of 3-hydroxybutyrate and medium chain length hydroxyalkan⇘te produced by Pseudomonas pseudoalkaligenus YS1. It was observed that there were some fixed ranges of C∶N molar ratio that affect the monomer composition of PHA independently of the substrate. For strain 0806, the ranges were C∶N <20, 20<C∶N<200, and C∶N>200. The monomer composition was constant among these ranges when using glucose and octanoate as the sole substrate. For strain YS1, the ranges were C∶N<20, 20<C∶N<45, and C∶N>45. These results are useful for controlling monomer composition in PHA production.     

Preparation and Characterization of Polyhydroxyalkanoates Macroporous Scaffold Through Enzyme-Mediated Modifications

Polyhydroxyalkanoates (PHAs) are hydrophobic biodegradable thermoplastics that have received considerable attention in biomedical applications due to their biocompatibility, mechanical properties, and biodegradability. In this study, the degradation rate was regulated by optimizing the interaction of parameters that influence the enzymatic degradation of P(3HB) film using response surface methodology (RSM). The RSM model was experimentally validated yielding a maximum 21 % weight loss, which represents onefold increment in percentage weight loss in comparison with the conventional method. By using the optimized condition, the enzymatic degradation by an extracellular PHA depolymerase from Acidovorax sp. DP5 was studied at 37 °C and pH 9.0 on different types of PHA films with various monomer compositions. Surface modification of scaffold was employed using enzymatic technique to create highly porous scaffold with a large surface to volume ratio, which makes them attractive as potential tissue scaffold in biomedical field. Scanning electron microscopy revealed that the surface of salt-leached films was more porous compared with the solvent-cast films, and hence, increased the degradation rate of salt-leached films. Apparently, enzymatic degradation behaviors of PHA films were determined by several factors such as monomer composition, crystallinity, molecular weight, porosity, and roughness of the surface. The hydrophilicity and water uptake of degraded salt-leached film of P(3HB-co-70%4HB) were enhanced by incorporating chitosan or alginate. Salt-leached technique followed by partial enzymatic degradation would enhance the cell attachment and suitable for biomedical as a scaffold.     

Current Advances towards 4-Hydroxybutyrate Containing Polyhydroxyalkanoates Production for Biomedical Applications

Polyhydroxyalkanoates (PHA) are polyesters having high promise in biomedical applications. Among different types of PHA, poly-4-hydroxybutyrate (P4HB) is the only polymer that has received FDA approval for medical applications. However, most PHA producing microorganisms lack the ability to synthesize P4HB or PHA comprising 4-hydroxybutyrate (4HB) monomer due to their absence of a 4HB monomer supplying pathway. Thus, most microorganisms require supplementation of 4HB precursors to synthesize 4HB polymers. However, usage of 4HB precursors incurs additional production cost. Therefore, researchers have adopted strategies to reduce the cost, such as utilizing low-cost substrate as well as constructing 4HB monomer supplying pathways in microorganisms. We herein summarize the biomedical applications of P4HB, the natural producers of 4HB polymer, and the various strategies that have been applied in producing 4HB polymers in non-4HB producing microorganisms. It is expected that the readers would gain a vivid idea on the different strategic developments in the field of 4HB polymer production.     

Biodegradation of a medium-chain-length polyhydroxyalkanoate in tropical river water

The medium-chain-length polyhydroxyalkanoate (PHA_MCL) produced by Pseudomonas putida PGA1 using saponified palm kernel oil as the carbon source could degrade readily in water taken from Kayu Ara River in Selangor, Malaysia. A weight loss of 71.3% of the PHA film occurred in 86 d. The pH of the river water medium fell from 7.5 (at d 0) to 4.7 (at d 86), and there was a net release of CO₂. In sterilized river water, the PHA film also lost weight and the pH of the water fell, but to lesser extents. The C8 monomer of the PHA was completely removed after 6 d of immersion in the river water, while the proportions of the other monomers (C10, C12, and C14) were reversed from that of the undegraded PHA. By contrast, the monomer composition of the PHA immersed in sterilized river water did not change significantly from that of the undegraded PHA. Scanning electron microscopy showed physical signs of degradation on the PHA film immersed in the river water, but the film immersed in sterilized river water was relatively unblemished. The results thus indicate that the PHA_MCL was degraded in tropical river water by biologic as well as nonbiologic means. A significant finding is that shorter-chain monomers were selectively removed throughout the entire PHA molecule, and this suggests enzymatic action.     

Improved synthesis of P(3HB-co-3HV-co-3HHx) terpolymers by mutant Cupriavidus necator using the PHA synthase gene of Chromobacterium sp. USM2 with high affinity towards 3HV

Unlike polyhydroxyalkanoates (PHAs) copolymers, the controlled and efficient synthesis of PHA terpolymers from triglycerides and fatty acids are yet to be established. This study demonstrates the production of P(3HB-co-3HV-co-3HHx) terpolymer with a wide range of 3HV monomer compositions from mixtures of crude palm kernel oil and 3HV precursors using a mutant Cupriavidus necator PHB⁻4 transformant harboring the PHA synthase gene (phaC) of a locally isolated Chromobacterium sp. USM2. The PHA synthase of Chromobacterium has an unusually high affinity towards 3HV monomer. P(3HB-co-3HV-co-3HHx) terpolymers with 3HV monomer composition ranging from 2 to 91 mol% were produced. Generation of 3HHx monomers was affected by the concentration and feeding time of 3HV precursor. P(3HB-co-24 mol% 3HV-co-7 mol% 3HHx) exhibited mechanical properties similar to that of common low-density polyethylene. P(3HB-co-3HV-co-3HHx) terpolymers with a wide range of 3HV molar fraction had been successfully synthesized by adding lower concentrations of 3HV precursors and using a PHA synthase with high affinity towards 3HV monomer.     

Recent developments in the design of functionalised polymeric microspheres

This paper is a brief survey on the preparation of latexes bearing covalently bonded functional groups using various routes. Recent methods are presented using water soluble functional (or surface active) initiators, monomers or macromonomers. For tailor synthesis, the copolymerisation approach of a basic monomer with a functional monomer under emulsifier-free conditions is generally the more suitable and versatile one. More progress should be pursued in this field in order to design better adapted chemical structures which will improve their use in radical-initiated heterogeneous conditions and favour surface incorporation.     

Utilization of 2-alkenoic acids for biosynthesis of medium-chain-length polyhydroxyalkanoates in metabolically engineered Escherichia coli to construct a novel chemical recycling system

This study describes the biosynthesis and thermal degradation of medium-chain-length polyhydroxyalkanoate (PHA), focusing on 2-alkenoic acids as a recyclable carbon source. Using metabolically engineered Escherichia coli, PHA consisting of 3-hydroxydecanoate (3HD) was synthesized from 2-decenoic acid. Solvent cast film of poly(3HD) [P(3HD)] was transparent and showed thermal property similar to that of polycaprolactone. In addition, the use of various 2-alkenoic acids (C6-C12) resulted in production of PHAs with over 95 mol% of the corresponding single monomer units. The pyrolysis product of P(3HD) was dominantly 2-decenoic acid used for the P(3HD) biosynthesis. This demonstrates the feasibility of PHA recycling via 2-alkenoic acids, which act as pyrolysis products and raw materials for PHA biosynthesis.     

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) by metabolically engineered Escherichia coli strains

Biosynthesis of polyhydroxyalkanoates (PHAs) consisting of 3-hydroxyalkanoates (3HAs) of 4 to 10 carbon atoms was examined in metabolically engineered Escherichia coli strains. When the fadA and/or fadB mutant E. coli strains harboring the plasmid containing the Pseudomonas sp. 61-3 phaC2 gene and the Ralstonia eutropha phaAB genes were cultured in Luria-Bertani (LB) medium supplemented with 2 g/L of sodium decanoate, all the recombinant E. coli strains synthesized PHAs consisting of C4, C6, C8, and C10 monomer units. The monomer composition of PHA was dependent on the E. coli strain used. When the fadA mutant E. coli was employed, PHA containing up to 63 mol% of 3-hydroyhexanoate was produced. In fadB and fadAB mutant E. coli strains, 3-hydroxybutyrate (3HB) was efficiently incorporated into PHA up to 86 mol%. Cultivation of recombinant fadA and/or fadB mutant E. coli strains in LB medium containing 10 g/L of sodium gluconate and 2 g/L of sodium decanoate resulted in the production of PHA copolymer containing a very high fraction of 3HB up to 95 mol%. Since the material properties of PHA copolymer consisting of a large fraction of 3HB and a small fraction of medium-chain-length 3HA are similar to those of low-density polyethylene, recombinant E. coli strains constructed in this study should be useful for the production of PHAs suitable for various commercial applications.