胶束增溶紫外分光光度法测定水溶性共聚物中苯乙烯的含量

紫外光谱分析表明，乙苯（EB）的吸收光谱与聚苯乙烯（PSt)的吸收光谱十分相似，在最大吸收峰处两者的摩尔吸光系数相当，因此，可将乙苯作为参比物，在十二烷基硫酸钠（SDS）的胶束介质中，测定水溶性丙烯酰胺－苯乙烯嵌段共聚物（PAM－b-PS)中苯乙烯的含量，与元素分析的结果进行了比较表明，以乙苯为参比物的胶束增溶紫外分光光度法可准确地测定水溶性丙烯酰胺－苯乙烯嵌段共聚物中苯乙烯的含量。     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

 本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

苯乙烯-甲基丙烯酸甲酯悬浮-乳液复合聚合过程中聚合物复合粒子组成的变化

采用苯乙烯(St)悬浮聚合过程中滴加甲基丙烯酸甲酯(MMA)乳液聚合组分,悬浮乳液复合聚合(SECP)方法,制备大粒径聚苯乙烯聚甲基丙烯酸甲酯(PS- PMMA)复合粒子.采用FTIR、1H- NMR、13C- NMR分析方法,研究SECP各个时期复合粒子中MMA- St链节摩尔比,发现悬浮粒子中MMA St链节摩尔比逐渐增大,而PMMA乳胶粒子中逐渐减少,表明悬浮相和乳液相间存在物质传递过程.悬浮粒子中MMA链节质量与MMA总投料质量比主要由乳胶粒子生成速率和乳胶粒子向悬浮粒子凝聚速率决定.最终得到的复合粒子除含PS和PMMA均聚物外,还含少量MMA-St共聚物.     

RI-UV双检测器GPC法测定SBS的分子量分布

SBS是一种新型的高分子材料,是苯乙烯-丁二烯的嵌段共聚物,它的聚苯乙烯(PS)段对紫外光有吸收,聚丁二烯(PB)段对紫外光无吸收。采用RI-UV(示差-紫外)双检测器GPC法同时测定此共聚物的分子量分布和组成分布,Runyon等在计算中假定:SBS分子的流体力学体积可看作相应组成的均聚物分子的流体力学体积之和,以及均聚物的校正曲线斜率相同,其SBS分子量的计算式为,     

苯乙烯/甲基丙烯酸甲酯共聚物组分的测定

用红外光谱和紫外光谱进行共聚物组分定量分析时,如果选择的谱带只与共聚物组分含量有关,而与序列结构无关,即可由均聚物的混合物定量分析得到校正工作曲线。共聚物在这些谱带上的吸光度相当于混合物的吸光度。 Kamiyama等人在用IR研究丙烯酸甲酯/苯乙烯(MA/St)共聚物时,发现羰基吸收峰(1730cm~(-1))的半峰高宽度与MA的含量有关;Gallo用UV研究苯乙烯/甲基丙烯酸甲酯(St/MMA)共聚物时发现263毫微米的吸光度和St.组分含量不是线性关系;     

一类近红外电致发光芴基共聚物的合成和性能研究

基于9,9-二辛基芴与窄带隙单体5,7-二(2-噻吩基)噻[3,4-b]并[1,4]二嗪(DTP),通过Suzuki偶合反应,合成了一系列无规窄带隙的芴基共聚物(PFO-DTP),并对它们的紫外-可见吸收光谱、光致发光和电致发光性能进行了初步研究.共聚物在380 nm和632 nm处有两个明显的吸收峰,其中632 nm处的吸收随着共聚物中窄带隙单体(DTP)含量的增加而加强,最大电致发光峰随着共聚物中窄带隙单体(DTP)含量的增加,从752nm红移到了781 nm.同时与其同分异构体4,7-二(2-噻吩基)苯并噻二唑(DBT)与芴的共聚物PFO-DBT相比,该类聚合物的吸收红移,与近地太阳光谱更为匹配.     

嵌段-接枝共聚物SEPG与PS(OH)之间的氢键络合导致胶束化的研究

利用原子转移自由基聚合反应合成了以聚苯乙烯-b-聚(乙烯-co-丙烯)(SEP)为主链、无规分布且数目可控的聚甲基丙烯酸乙酯(PEMA)为支链的嵌段接枝共聚物SEPG.发现在甲苯中因支链PEMA与聚(苯乙烯-co-对六氟羟丙基-α-甲基苯乙烯)[简称PS(OH]的氢键络合作用和EP嵌段的溶解作用导致了聚集体的胶束化.研究了胶束的尺寸及其分布对PS(OH)中羟基含量和共混物组成的依赖性.     

共聚物组成对线形苯乙烯-丁二烯-苯乙烯嵌段共聚物粘弹弛豫与相形态的影响

研究了不同组成的苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)的相形态与粘弹弛豫.用透射电子显微镜(TEM)表征了SBS的形态,结果显示,几种SBS均呈层状结构,随着苯乙烯含量的降低,聚苯乙烯(PS)相的尺寸稍有减小,而聚丁二烯(PB)相尺寸明显增大.用动态流变学方法考察了不同温度下SBS嵌段大分子的弛豫行为,结果表明,苯乙烯含量减少,PS相玻璃化转变和有序-无序转变温度均降低;苯乙烯含量少的,在有序-无序转变过程中呈现出高且宽的损耗峰,表明有序-无序转变过程中能量的耗散主要由两相溶合时分子链间的内摩擦所决定,分子链越长,内摩擦越大,能量耗散越大.     

苯乙烯-异戊二烯两嵌段共聚物溶液的dn/dc和紫外吸收光谱

本文研究了苯乙烯-异戊二烯两嵌段共聚物在CHCl_3中的折光指数浓度增量(dn/dc)和紫外吸收光谱。嵌段共聚物dn/dc具有很好的加和性,可以测定嵌段共聚物的组成。紫外吸收光谱的结果表明,除低苯乙烯含量的样品外,其它嵌段共聚物都显示明显的紫外增色性(UV hyperchromism)。因此UV和UV-RI双检测GPC不会得到可靠的嵌段共聚物组成数据。这种增色现象与其特征的紫外吸收谱图紧密关联     

CHARACTERIZATION OF AMPHIPHILIC AND MICROPHASE SEPARATED GRAFT COPOLYMERS Ⅱ SURFACE CHARACTERIZATION AND IN VITRO BLOOD-COMPATIBILITY ASSESSMENT OF POLYSTYRENE-GRAFT-ω-STEARYLPOLY (ETHYLENE OXIDE)*

This paper reported the research results concerning the surface characterization ofpolystyrene-graft-w-stearyl poly(ethylene oxide) (PS-g-SPEO) by means of XPS,contactangle measurement and TEM, and its in vitro blood compatibility assessment by measuringthe plasma recalcification time (RT) and partial thromboplastin time (PTT). The XPSresults demonstrated that the surface and bulk composition of the PS-g-SPEO graftcopolymers differ remarkably from each other,and that SPEO component was constantlyenriched at the copolymer/air interface. Contact angle studies indicated that the surfacewater wettability can be adjusted effectively by changing the composition of the copolymer.PS-g-SPEO graft copolymers can undergo microphase separation as clearly illustrated byTEM photographs. The relationship between the surface properties of PS-g-SPEO graftcopolymer and its blood compatibility was also discussed.     

Synthesis, Purification and Characterization of Amphiphilic and Microphase Separated Graft Copolymer Polystyrene-g-Poly(ethylene oxide)

The present paper covers the poly (ethylene oxide) macromer with vinyl benzyl terminal group (PEO-VB) prepared by deactivation of the alkoxide function of mono-functional "living" PEO chains with vinyl benzyl chloride (VBC). The obtained macromers were subjected to careful purification and detailed characterization. A new kind of amphiphilic polystyrene-g-poly(ethylene oxide) (PS-g-PEO) with both mi-crophase separated and PEO side chains was synthesized from radical copolymerization of PEO-VB macromer with styrene monomer. An improved purification method, referred as "selective dissolvation", was established for the isolation of graft copolymers from the grafting products, and the purity and yield of the purified copolymers were satisfactory. The well-defined structure of the purified copolymers was confirmed by IR, 1H NMR and GPC. The bulk composition of the graft copolymers was determined by a well-established first derivative UV spectrometry. Various experimental parameters controlling the copolymeri     

Application of solid phase peptide synthesis to engineering PEO–peptide block copolymers for drug delivery

This work describes a simple, versatile solid-phase peptide-synthesis (SPPS) method for preparing micelle-forming poly(ethylene oxide)-block-peptide block copolymers for drug delivery. To demonstrate its utility, this SPPS method was used to construct two series of micelle-forming block copolymers (one of constant core-composition and variable length; the other of constant core length and variable composition). The block copolymers were then used to study in detail the effect of size and composition on micellization. The various block copolymers were prepared by a combination of SPPS for the peptide block, followed by solution–phase conjugation of the peptide block with a proprionic acid derivative of poly(ethylene oxide) (PEO) to form the PEO-b-peptide block copolymer. The composition of each block component was characterized by mass spectrometry (MALDI and ES-MS). Block copolymer compositions were characterized by ¹H NMR. All the block copolymers were found to form micelles as judged by transmission electron microscopy (TEM) and light scattering analysis. To demonstrate their potential as drug delivery systems, micelles prepared from one member of the PEO-b-peptide block copolymer series were physically loaded with the anticancer drug doxorubicin (DOX). Micelle static and dynamic stability were found to correlate strongly with micelle core length. In contrast, these same micellization properties appear to be a complex function of core composition, and no clear trends could be identified from among the set of compositionally varying, fixed length block copolymer micelles. We conclude that SPPS can be used to construct biocompatible block copolymers with well-defined core lengths and compositions, which in turn can be used to study and to tailor the behavior of block copolymer micelles.     

ESR spectroscopy to determine the molecular mobility of poly(ethylene oxide) grafts in amphiphilic graft copolymers

The ethylene oxide (EO) mobility in polystyrene-graft-[poly(ethylene oxide)] (PS-g-PEO) and polystyrene-graft-[stearyl poly(ethylene oxide)] (PS-g-SPEO) copolymers was evaluated by spin probe techniques. The ESR spectra indicate that 4-hydroxyl-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) is strongly biased to the PEO phase of the PS-g-(S)PEO membranes. The rotational correlation time τ_c can also be employed to assess the PEO mobility in PS-g-(S)PEO membranes. Although τ_c of PS-g-(S)PEO usually decreases with increasing surface density of EO, it is of interest that τ_c is rather high when the surface within a depth of at least 5 nm is fully occupied by SPEO (sample PS-g-SPEO-72.6).     

A New Interpretation of Contact Angle Variations in View of a Recent Analysis of Immersion Calorimetry

Surface properties of the polystyrene-graft-omega-stearyl-poly(ethylene oxide) (PS-g-SPEO) have been characterized by X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), contact angle, and spin probe techniques. The XPS results indicate that the surface and bulk composition of the PS-g-SPEO copolymers differ remarkably from each other. The stearyl and EO components enrich at the copolymer/air interfaces due to the self-assembly of the stearyl groups. At the PS-g-SPEO-72.6 surface (the x in PS-g-SPEO-x indicates the bulk density of the SPEO in wt%), the self-assembly of the hydrophobic stearyl groups is strong enough to form a stable liquid crystalline phase as indicated by DSC. At polymer/water interfaces, PS-g-SPEO-72.6 presents a hydrophilic surface with low PEO mobility, whereas PS-g-SPEO-50.6 and PS-g-SPEO-31.0 present the hydrophobic surface with high PEO mobility. The two different types of the surfaces, with different characters in surface energy, surface mobility of PEO, and surface architecture of SPEO, will be quite valuable as models for detecting the synergistic action of the PEO chains and the stearyl groups (specific ligand for albumin binding) in protein solutions. Copyright 2000 Academic Press.     

Synthesis of poly(styrene-graft-ethylene oxide) by ethoxylation of amide group containing styrene copolymers

Graft copolymers containing poly(ethylene oxide) side chains on a polystyrene backbone have been synthesized. Styrene copolymers synthesized by free radical mechanism and containing between 5 and 15 mol % acrylamide or methacrylamide were used as backbones. The amide groups in the copolymers were ionized by using potassium tert-butoxide or potassium naphthalene, and grafting was achieved by utilizing the amide anions as initiator sites for the polymerization of ethylene oxide in 2-ethoxyethyl ether at 65°C. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, NMR, gel permeation chromatography, IR, and viscosity measurements. The size of the side chains were between 600 and 2000 g/mol. GPC results from a hydrolyzed graft copolymer sample suggest a narrow size distribution for the poly(ethylene oxide) grafts. Solution properties of the graft copolymers were investigated in different toluene/methanol mixtures. The intrinsic viscosities of the graft copolymers were found to depend primarily on the poly(ethylene oxide) content rather than the graft density or the poly(ethylene oxide) chain length. © 1993 John Wiley & Sons, Inc.     

An Efficient Approach for Preparing Giant Polypeptide Triblock Copolymers by Protein Dimerization

An efficient and convenient approach for preparing a giant polypeptide–poly(ethylene oxide) triblock copolymer architecture of defined structure and composition is reported. This copolymer consists of two long polypeptide chains derived from bovine serum albumin of distinct lengths with stabilizing poly(ethylene oxide) side‐chains, a connecting poly(ethylene oxide) block, and the presence of secondary structure elements along the polypeptide backbone. It is synthesized from the abundant plasma protein serum albumin and the polypeptide backbone is fully biodegradable. This approach represents a convenient and efficient strategy for preparing giant polypeptide‐based block copolymers of defined structure via a semi‐synthetic strategy. Such high‐molecular‐weight, biodegradable copolymers are attractive for various biomedical applications     

Effects of block architecture and composition on the association properties of poly(oxyalkylene) copolymers in aqueous solution

A block copolymer of hydrophilic poly(ethylene oxide) and a hydrophobic poly(alkylene oxide) can associate in dilute aqueous solution to form micelles. The results of recent investigations of the micellisation behaviour and micelle properties of such copolymers are described. Copolymers of ethylene oxide with propylene oxide, 1,2‐butylene oxide or styrene oxide are considered, including aspects of their preparation. Experimental methods for determination of critical conditions for micellisation, micelle association number and spherical‐micelle radius are summarised. Effects of temperature, composition, block length and block architecture (diblock, triblock and cyclic‐diblock) are described and, where possible, related to the predictions of theory. Brief consideration is given to the dynamics of micelle formation/dissociation, to cylindrical micelles, and to effects of added salts.     

Poly(vinyl chloride)–poly(ethylene oxide) block copolymers: Synthesis and characterization

Poly(vinyl chloride)-poly(ethylene oxide) block copolymers have been synthesized in solution and emulsion. The polymers were made by first synthesizing macroazonitriles through the reaction of 4,4′-azobis-4-cyanovleryl chloride with hydroxy-terminated poly(ethylene oxide) of varying molecular weights. These macroazonitriles had molecular weights in the range of 3000–88,000 and degrees of polymerization from 5 to 24. Thermal decomposition of the azolinkages in the presence of vinyl chloride monomer yielded block copolymers containing form 2 to 20 wt % poly(ethylene oxide). The structures of the block copolymers were characterized by spectrometric, elemental and molecular weight analyses. The possibility of some graft polymerization occurring via free-radical extraction of a methylene hydrogen from the poly(ethylene oxide) was considered. Polymerization of vinyl chloride with an azonitrile initiator in the presence of a poly(ethylene oxide) yielded predominately homopolymer with some grafted poly(vinyl chloride).     

Synthesis and characterization of ABA‐type amphiphilic tri‐block copolymers through anionic polymerization using end functionalized poly(ethylene oxide) oligomers

ABA‐type amphiphilic tri‐block copolymers were successfully synthesized from poly(ethylene oxide) derivatives through anionic polymerization. When poly(styrene) anions were reacted with telechelic bromine‐terminated poly(ethylene oxide) ( 1 ) in 2:1 mole ratio, poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers were formed. Similarly, stable telechelic carbanion‐terminated poly(ethylene oxide), prepared from 1,1‐diphenylethylene‐terminated poly (ethylene oxide) ( 2 ) and sec‐BuLi, was also used to polymerize styrene and methyl methacrylate separately, as a result, poly (styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) and poly (methyl methacrylate)‐b‐poly(ethylene oxide)‐b‐poly(methyl methacrylate) tri‐block copolymers were formed respectively. All these tri‐block copolymers and poly(ethylene oxide) derivatives, 1 and 2 , were characterized by spectroscopic, calorimetric, and chromatographic techniques. Theoretical molecular weights of the tri‐block copolymers were found to be similar to the experimental molecular weights, and narrow polydispersity index was observed for all the tri‐block copolymers. Differential scanning calorimetric studies confirmed the presence of glass transition temperatures of poly(ethylene oxide), poly(styrene), and poly(methyl methacrylate) blocks in the tri‐block copolymers. Poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers, prepared from polystyryl anion and 1 , were successfully used to prepare micelles, and according to the transmission electron microscopy and dynamic light scattering results, the micelles were spherical in shape with mean average diameter of 106 ± 5 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011