One‐pot regioselective and stereoselective terpolymerization of rac‐lactide,CO2 and rac‐propylene oxide with TPPMCl (M = Cr,Co, Al)/PPNCl binary catalyst

Tetraphenyl porphyrin metal compound (TPPMCl) (where the TPPMCl was TPPCrCl, TPPCoCl, TPPAlCl), in combination with cocatalyst PPNCl (bis(triphenylphosphine)iminium chloride, the molar ratio of TPPMCl to PPNCl was 1:0.5), was used to catalyze the polymerization of racemic lactide (rac‐LA) in racemic propylene oxide (rac‐PO) medium and the terpolymerization of rac‐LA, CO₂ and rac‐PO. It was found that these TPPMCl/PPNCl binary catalysts could initiate the stereoselective polymerization of rac‐LA in rac‐PO medium to form enriched isotactic polylactide (PLA) (P_i ≥ 68.0%) and terpolymerization of CO₂, rac‐LA, rac‐PO to form PPC‐PLA‐PPO (PPC, poly(propylene carbonate); PPO, poly(propylene oxide)) multiblock copolymer. In particular the PPC‐PLA‐PPO multiblock copolymer thus formed displayed high regioregularity and stereoregularity, and has high head‐to‐tail structure content in the PPC block (H‐T% ≥ 63.6%) and high isotacticity in the PLA block (P_i ≥ 64.0%). The influence of catalyst formula, the monomer feeding ratio, reaction temperature, carbon dioxide pressure and reaction time on the terpolymerization was investigated by ¹H NMR, ¹³C NMR, gel permeation chromatography, DSC and TGA. © 2018 Society of Chemical Industry     

Synthesis,characterization and catalytic activity of zinc complex for ring‐opening polymerization of lactide

In the present study, salicylaldimine zinc complex (Zn‐HMBED) was synthesized and its reactivity for the ring‐opening polymerization (ROP) of lactide was studied. The zinc complex was prepared by the reaction of zinc solution with one molar equivalent of salicylaldimine Schiff base ligand in methanol under a nitrogen atmosphere. Further, the complex was characterized by various spectroscopic methods, which showed tetrahedral geometry. X‐ray diffraction studies were used for the structure determination of the Schiff base. It was observed that the zinc complex is highly active towards the ROP of lactide. The rate of polymerization is heavily dependent on the initiator used. The zinc complex allows controlled ROP as revealed by the linear relationship between the percentage conversion and the number‐average molecular weight. Finally, a mechanism for the ROP of lactide is proposed by use of the above zinc complex. © 2016 Society of Chemical Industry     

新型生物降解交联剂的制备及其在壳聚糖交联膜中的应用

本文用聚乙二醇和丙交酯在辛酸亚锡的催化作用下合成了可降解的二羟基中间体,再与2,4-甲苯二异氰酸酯(2,4-TDI)反应,合成了异氰酸酯基封端的一系列生物降解型交联剂.并且对中间体和交联剂进行了 FTIR分析表征.应用交联剂对壳聚糖膜材料进行交联,并对交联材料进行了吸水率,表面接触角及力学性能的测定,结果表明新型生物降解交联剂的运用不仪改善了材料吸水性,也提高了材料的力学性能.     

生物降解材料聚乳酸的合成

系统地介绍了包括丙交酯二步法、乳酸溶液聚合法和乳酸熔融聚合法在内的各种聚乳酸合成方法；并从安全和经济的观点出发，对聚乳酸的合成研究方向进行了展望，指出使用安全无毒的催化剂进行乳酸直接熔融聚合生产聚乳酸尤其值得大力开发。     

PLA单体--丙交酯合成方法的研究进展

只有高分子量聚乳酸才能满足组织工程对其强度及其它性能的要求，而丙交酯是制备高分子量聚乳酸的重要原料，其纯度和成本的高低决定了高分子量聚乳酸的质量和价格，20世纪70年代以来，在提高丙交酯的产率，纯度，降低丙交酯的成本方面做了大量的工作，并取得一定的进展，文中综述了制备丙交酯的各种方法和工艺，并讨论了各自的优缺点，提出了制备丙交酯和高分子量聚乳酸的可能发展方向。     

基于乳酸和哌嗪的聚碳酸酯酰胺的合成与表征

以丙交酯(LAD)和哌嗪(PPZ)为原料通过熔融反应制得酰胺二醇单体(HO-LA-PPZ-LA-OH),再经N,N’-羰基二咪唑(CDI)偶联聚合生成一种新型的含乳酸聚合物——聚碳酸酯酰胺(CDI-LA-PPZ-LA)。采用红外光谱、核磁共振和差示扫描量热分析等对材料进行了表征。结果表明,HO-LA-PPZ-LA-OH和CDI-LA-PPZ-LA已被成功合成;聚合物的玻璃化转变起始温度为84.3℃,数均相对分子质量为4328。后续的研究需要进一步提高CDI-LA-PPZ-LA的相对分子质量,以拓展其作为组织修复材料的应用。     

对二氧环己酮与丙交酯共聚反应的~1H-NMR分析

由对二氧环己酮（PDO）和丙交酯（LA）单体,在不同温度下合成了PDO-co-LA共聚物,采用核磁共振（1H-NMR）研究了共聚反应动力学和共聚物分子链结构,提出了一种链段平均序列长度的计算方法。结果显示,丙交酯在共聚反应中的聚合能力要比对二氧环己酮强;实验条件下LA/PDO投料物质的量比为2/3时,共聚物中PDO与L...     

Studies of different kinds of fiber pretreating on the properties of PLA/sweet sorghum fiber composites

In this article, truly degradable composites were prepared using sweet sorghum fibers which are residue of ethanol fermentation industry as reinforcement and renewable resource‐based biodegradable polyester, poly(L ‐lactide) (PLLA) as matrix, they were fabricated by melt‐blending. The effect of different kinds of pretreatments (dilute sulfuric acid pretreatment, mild alkaline/oxidative pretreatment, steam explosion pretreatment) on mechanical properties of composites were investigated. Besides the composition of untreated and treated fibers as determined by Van soest method, Fourier transformed infrared (FTIR) spectroscopic and scanning electron microscopic (SEM) were also used to study the change of sweet sorghum fibers before and after pretreatments. Mechanical properties testing indicated that tensile strength and impact strength of PLLA/treated fibers were improved except the dilute sulfuric acid pretreated fibers reinforced PLA composite. The mild alkaline/oxidative pretreated fiber reinforced PLA composite showed highest tensile strength of 46.12 MPa and impact strength of 8.02 kJ/m² which was 15.5 and 33% higher than that of the control. The SEM of impact fracture surface and DMTA test were carried out to investigate the interfacial morphology and interfacial adhesion between the fiber and matrix. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010