Synthesis and characterization of novel triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(γ-benzyl L-glutamate)s as outer blocks

Background Bioactive and biodegradable polyurethanes (BDPUs) have drawn much attention in recent years. As part of the research program to search for novel prepolymers for BDPUs, a study was carried out on the synthesis and characterization of triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(γ-benzyl L-glutamate)s as outer blocks. Results A new macroinitiator terminated with phenylalanine was first prepared from the condensation of a distal hydroxy poly(tetrahydrofuran) with N-tert-butoxycarbonyl L-phenylalanine in the presence of dicyclohexylcarbodiimide, followed by removing the protecting group. Then, it was employed to initiate the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride in varying feeding ratios to give rise to the targeted triblock copolymers. Conclusions The length of the outer poly(γ-benzyl L-glutamate) blocks was well tailored by varying the monomers to macroinitiator feeding ratio. All the triblock copolymers exhibited a nearly symmetrical and unimodal molecular weight distribution while only one distinct glass transition temperature was evidenced from −10°C to 25°C.     

环型四氢呋喃齐聚物的合成与表征

首次采用丁二酰氯和１,４－二溴甲苯与线型双端羟基四氢呋喃齐聚物进行进行分子内的成环反应,制得了环型四氢呋喃聚醚,综合沉淀分级试样的绝对分了阳的测定,端基测定,红外光谱和核磁共振测定结果证明,合成产物系环型四氢呋喃齐聚物。     

Synthesis of well-defined star-branched polymers by stepwise iterative methodology using living anionic polymerization

This article reviews the synthesis of regular and asymmetric star-branched polymers with well-defined structures by methodologies using living anionic polymerization, especially focusing on the synthetic approaches accessible for precisely controlled architectures of star-branched polymers concerning molecular weight, molecular weight distribution, arm number, and composition. The reason for selecting living anionic polymerization from many living/controlled polymerization systems so far developed is that this living polymerization system is still the best to meet the strict requirements for the precise structures of star-branched polymers. Furthermore, we herein mainly introduce a novel and quite versatile stepwise iterative methodology recently developed by our group for the successive synthesis of many-armed and multi-compositional asymmetric star-branched polymers. The methodology basically involves only two sets of the reaction conditions for the entire iterative synthetic sequence. The reaction sequence can be, in principle, limitlessly iterated to introduce a definite number of the same or different polymer segments at each stage of the iteration. As a result, a wide variety of many-armed and multi-compositional asymmetric star-branched polymers can be synthesized.     

PPG/PTHF对MC尼龙结晶行为的影响

采用DSC、SEM、解偏振光法研究了共聚醚对MC尼龙结晶行为的影响,发现PPG/PTHF-PA共聚物是一个半相容体系,不同分子量的共聚醚与MC尼龙的相容性不同,随着共聚醚分子量、含量的增加,相容性、结晶度呈现先上升而后下降峰形变化,球晶变小,结晶也不完善.共聚醚在MC尼龙结晶过程中起异相成核作用.研究发现,PPG/PTHF部分向尼龙部分渗透,在尼龙保持完整球晶同时,PPG/PTHF能均匀分散在PA基体中,此时共聚物具有优良的力学性能.     

The synthesis of PHA‐g‐(PTHF‐b‐PMMA) multiblock/graft copolymers by combination of cationic and radical polymerization

A new and promising method for the diversification of microbial polyesters based on chemical modifications is introduced. Poly(3‐hydroxy alkanoate)‐g‐(poly(tetrahydrofuran)‐b‐poly(methyl methacrylate)) (PHA‐g‐(PTHF‐b‐PMMA)) multigraft copolymers were synthesized by the combination of cationic and free radical polymerization. PHA‐g‐PTHF graft copolymer was obtained by the cationic polymerization of THF initiated by the carbonium cations generated from the chlorinated PHAs, poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHx) in the presence of AgSbF₆. Therefore, PHA‐g‐PTHF graft copolymers with hydroxyl ends were produced. In the presence of Ce⁺⁴ salt, these hydroxyl ends of the graft copolymer can initiate the redox polymerization of MMA to obtain PHA‐g‐(PTHF‐b‐PMMA) multigraft copolymer. Polymers obtained were purified by fractional precipitation. In this manner, their γ‐values (volume ratio of nonsolvent to the solvent) were also determined. Their molecular weights were determined by GPC technique. The structures were elucidated using ¹H‐NMR and FTIR spectroscopy. Thermal analyses of the products were carried out using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

聚醚偶联剂改性碳酸钙及CaCO_3/PP复合材料的性能

自制了偶联剂四氢呋喃均聚醚(PTHF),并用其对轻质碳酸钙表面进行处理,将处理后的碳酸钙填充到聚丙烯塑料中,探讨了新型改性剂对复合材料力学性能的影响。结果表明,四氢呋喃均聚醚能够使碳酸钙的吸油值降低到22%,接触角降低到68.6°。改性后的碳酸钙填充进聚丙烯,能在一定程度上缓解拉伸强度的下降趋势,使复合材料的断裂伸长率达到28.47%、冲击强度达到6.7kJ/m2。SEM观察四氢呋喃均聚醚添加前后复合材料的断面形态,表明碳酸钙在聚丙烯中分散良好。     

Telechelic polymers by living and controlled/living polymerization methods

Telechelic polymers, defined as macromolecules that contain two reactive end groups, are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. This review article describes the general techniques for the preparation of telechelic polymers by living and controlled/living polymerization methods; namely atom transfer radical polymerization, nitroxide mediated radical polymerization, reversible addition-fragmentation chain transfer polymerization, iniferters, iodine transfer polymerization, cobalt mediated radical polymerization, organotellurium-, organostibine-, organobismuthine-mediated living radical polymerization, living anionic polymerization, living cationic polymerization, and ring opening metathesis polymerization. The efficient click reactions for the synthesis of telechelic polymers are also presented.     

黏合剂结构对胶片及推进剂力学性能的影响

为了阐明黏合剂结构对推进剂力学性能的影响,采用动态力学和单项拉伸试验方法,研究了几种典型聚酯聚醚黏合剂结构对推进剂力学性能的影响。结果表明,在不含增塑剂情况下,聚四氢呋喃(PTHF)胶片具有更高的伸长率,聚己内酯-四氢呋喃嵌段聚酯醚(HTCE)和聚己内酯(PCL)具有更高的强度;PCL、HTCE和PTHF胶片的储能模量(E′)和损耗模量(E″)依次降低,其玻璃化转变温度(T_g)分别为-43.94、-61.99和-66.98℃。增塑剂降低了链段解冻运动过程中的内耗阻力,使胶片的玻璃化温度大幅降低,PTHF、PCL和HTCE的T_g分别为-67.66、-72.27和-77.10℃,PCL的储能模量和损耗模量最高,PTHF储能模量大于HTCE、HTCE和PCL胶片的力学性能优于PTHF。推进剂的T_g由高到低顺序为PTHF、PCL、HTCE,分别为-55.27、-56.16和-57.91℃;PTHF的储能模量最大,在低温下抗冲击性能和韧性最差;HTCE推进剂的储能模量和损耗模量最低,黏合剂体系的弹性较好、损耗较低;PCL的储能模量、损耗模量和内耗峰面积均较高,在宽温度范围内的刚性和冲击韧性较好。     

负载型蒙脱土(Fe_2O_3/H-MMT)催化合成聚四氢呋喃

研究了蒙脱土(MMT)负载硝酸铁制备的固体酸催化剂(Fe2O3/H-MMT)在四氢呋喃(THF)开环聚合中的催化性能。考察了催化剂的制备条件和乙酸酐用量对催化活性和聚四氢呋喃(PTHF)粘均相对分子质量的影响。结果表明,在酸化处理用酸浓度为3.00 mo.lL-1,Fe2O3负载量为18%(质量分数),焙烧温度为400℃下制备的催化剂,反应5 h,催化活性为1.17 g.g-1Cat.h-1。催化活性随乙酸酐用量的增加而增大。催化剂的制备条件对PTHF的相对分子质量影响不大,受乙酸酐用量的影响。     

Functionalization of carbon nanomaterials for advanced polymer nanocomposites: A comparison study between CNT and graphene

The allotropes of carbon nanomaterials (carbon nanotubes, graphene) are the most unique and promising substances of the last decade. Due to their nanoscale diameter and high aspect ratio, a small amount of these nanomaterials can produce a dramatic improvement in the properties of their composite materials. Although carbon nanotubes (CNTs) and graphene exhibit numerous extraordinary properties, their reported commercialization is still limited due to their bundle and layer forming behavior. Functionalization of CNTs and graphene is essential for achieving their outstanding mechanical, electrical and biological functions and enhancing their dispersion in polymer matrices. A considerable portion of the recent publications on CNTs and graphene have focused on enhancing their dispersion and solubilization using covalent and non-covalent functionalization methods. This review article collectively introduces a variety of reactions (e.g. click chemistry, radical polymerization, electrochemical polymerization, dendritic polymers, block copolymers, etc.) for functionalization of CNTs and graphene and fabrication of their polymer nanocomposites. A critical comparison between CNTs and graphene has focused on the significance of different functionalization approaches on their composite properties. In particular, the mechanical, electrical, and thermal behaviors of functionalized nanomaterials as well as their importance in the preparation of advanced hybrid materials for structures, solar cells, fuel cells, supercapacitors, drug delivery, etc. have been discussed thoroughly.