聚苯乙烯大分子单体与丙烯酸丁酯的接枝共聚

Milkovich等曾报道,用阴离子型活性聚合方法可合成一系列分子量分布均匀、聚合物链端带有可聚合基团的大分子单体(Macromer),它可进一步以任何聚合方法与第二单体共聚,合成具有一定长度侧链的梳型或T型接枝共聚物。由于Macrom-er与第二单体的多变性,因此,通过这一途径可以开发一系列具有特殊性能的新型高分子材料。     

新型聚乙烯-g-聚乳酸接枝共聚物的合成与表征

报道了一类主链为聚乙烯(PE)共聚物,侧链为生物基聚乳酸(PLA)的新型接枝共聚物及其制备方法,并对接枝共聚物结构与性能进行了深入的表征。采用配位聚合与开环聚合相结合的方法,以羟基功能化的聚乙烯共聚物为主链,通过羟基引发L-丙交酯(L-LA)的开环聚合,从而获得聚乙烯-g-PLA接枝共聚物。通过控制单体比例和反应条件,可同时实现接枝共聚物的主链结构以及侧链结构调控。结果表明,少量PLA接枝链的引入可在不明显降低拉伸强度的情况下,有效地改善接枝共聚物的断裂伸长率。热性能表征发现侧链PLA的引入限制了主链聚乙烯的结晶,造成了接枝共聚物结晶温度以及熔点的下降。该接枝共聚物展现出了可用于PLA等生物基聚酯材料的增韧改性或共混增容剂的应用潜力,也为此类接枝共聚物的合成与性能调控提供了重要的参考。     

孪尾疏水缔合丙烯酰胺/丙烯酸钠/N,N-二丁基丙烯酰胺共聚物的合成与性能

以十二烷基硫酸钠(SDS)为表面活性剂,丙烯酰胺(AM)的水溶液为连续相,N,N-二丁基丙烯酰胺(DiC4AM)为分散相,采取先加碱共聚-共水解的方法合成了孪尾疏水缔合水溶性聚合物聚(丙烯酰胺/丙烯酸钠/N,N-二丁基丙烯酰胺)[P(AM/NaAA/DiC4AM)]。用FT IR1、H NMR对其结构、组成进行了表征和测定。用稀释外推粘度法测定了共聚物的特性粘数[η]、Huggins常数KH。用芘荧光探针法及表观粘度法研究了大分子链间的疏水缔合作用,考察了疏水单体用量对其水溶液表观粘度的影响。     

丙烯酸酯类与聚苯乙烯大单体接枝共聚物结构及性能的研究

通过“大单体技术”合成了不同分子量、组成和微观结构的接枝共聚物(骨架为聚丙烯酸丁酯或聚甲基丙烯酸甲酯,侧链为聚苯乙烯),测定了它们的组成和微观结构,并研究了这类接枝共聚物的微观分相,以及光学、力学和表面等性能。     

端基对大单体共聚活性及聚羧酸减水剂侧链分布的影响

为研究大单体端基对其共聚活性及形成共聚物结构的影响,测定了甲基烯丙基聚乙二醇醚(MAPEG)、异戊烯基聚乙二醇醚(IPEG)、乙氧基乙烯基聚乙二醇醚(VEPEG)与丙烯酸(AA)进行自由基水溶液共聚反应时的单体竞聚率,通过核磁共振氢谱(1H NMR)和前线轨道理论分析3种大单体共聚活性,对比了3组共聚合过程及共聚物微观结构的差异。结果表明:MAPEG和IPEG单体的化学结构及共聚合活性十分相似,而具有不同端基的VEPEG大单体有不同的共聚合活性;VEPEG-AA共聚体系的大单体转化率与MAPEG-AA和IPEG-AA共聚体系变化趋势相反。MAPEG-co-AA与IPEG-co-AA共聚物的侧链密度及侧链分布基本相同,VEPEG-co-AA共聚物侧链密度始终较低;但随着大单体加料量增加,大单体活性和共聚过程的差异使3种共聚物侧链密度差异变小。     

聚(丙烯酸-丙烯酰胺)接枝辛基酚聚氧乙烯醚丙烯酸酯两亲性共聚物的合成及表征

以辛基酚聚氧乙烯醚丙烯酸酯(C8PhEO10Ac)为大分子单体,丙烯酸(AA)、丙烯酰胺(AM)为共聚单体,采用大分子单体接枝共聚法,制备了一种两亲性接枝共聚物(AA-AM-g-C8PhEO10Ac),用静态光散射(SLS)与GPC联用技术测得接枝共聚物的分子量为9.51×105,用FTIR、1H NMR和TG/DTA等手段对共聚物的结构及性能进行了表征。采用透射电子显微镜(TEM)对聚合物在水溶液中的自组装行为进行了初步研究。结果表明,AA-AM-g-C8PhEO10Ac在水溶液中自组装,形成球型胶束,随着浓度增大,趋向于形成更大的自组装体。     

N-异丙基丙烯酰胺功能性共聚物的结构及特性研究进展

N-异丙基丙烯酰胺共聚物是一种新型的智能材料,可用于制备药物控释材料、酶的固定材料、脱水剂等。概述了N-异丙基丙烯酰胺共聚物及其各类共聚单体的大分子结构、氢键效应及刺激响应性等特性。     

原子转移自由基聚合在聚合物分子设计中的应用

原子转移自由基聚合反应 ( ATRP)是一种新的活性自由基聚合方法 ,自 1995年提出后 ,引起高分子合成化学及工业界的关注。本文详细介绍了 ATRP在端功能基聚合物、大分子单体、嵌段共聚物、接枝共聚物、星形聚合物、梯度共聚物、超支化聚合物等聚合物分子设计中的应用     

超支化聚(胺-酯)-丙烯酸共聚物的合成

利用端单羟基超支化聚(胺-酯)与丙烯酰氯反应,制备了端基为双键的超支化聚(胺-酯)大分子单体(cHPAE),用该大分子单体与丙烯酸发生共聚合,合成了超支化聚(胺-酯)-聚丙烯酸共聚物(HPAE-co-AA),利用FTIR和1HNMR对大分子单体结构进行了表征,研究了反应条件对共聚产物分子量的影响.结果表明:共聚反应溶剂...     

基于点击化学和可逆加成-断裂链转移自由基聚合合成极性链接枝聚丁二烯

以1-硫代甘油作为改性剂、聚丁二烯为主链,通过热引发和光引发合成了侧基含有羟基的聚丁二烯,以S-1-十二烷基-S′（α-α′-二甲基-α′′乙酸）-三硫代碳酸酯作为可逆加成-断裂链转移自由基聚合试剂、偶氮二异丁腈为引发剂,合成了端羧基聚N,N-二甲基丙烯酰胺,然后将两种官能化的聚合物进行酯化反应制得聚N,N-二甲基丙烯酰胺接枝聚丁二烯。结果表明,采用光引发可以显著提高点击化学的反应效率。用核磁共振氢谱证实了产物含羟基聚丁二烯和端羧基聚N,N-二甲基丙烯酰胺以及接枝聚合物的结构,并显示通过这种方法所制备接枝聚合物的接枝链数目和长度均可控。     

Rheological Behaviour of Poly (Acrylamide-G-Propylene Oxide) Solutions: Effect of Hydrophobic Content,Temperature and Salt Addition

Abstract

The viscosity of hydrophobically modified polyacrylamide was investigated as a function of polymer concentration in aqueous and in salt solutions, and also as a function of temperature. The graft copolymers were constituted of polyacrylamide backbone and different amount of hydrophobic polypropylene oxide) graft chains. Measurements of intrinsic viscosities have been performed by using a Contraves low-shear LS-40 rheometer. From these results, a dependence of the intrinsic viscosity of the polymer solution with the molecular weight was observed, where an increase of the latter resulted in higher intrinsic viscosity. In this case, the effect of the molecular weight was more emphasized than the effect caused by the slightly different degrees of hydrophobic incorporation. When enhancing the temperature, it was not verified a significant change on the reduced viscosities of the copolymer solutions and the graft chain length was also observed.     

Synthesis and solution properties of poly(acrylamide-styrene) block copolymers with high hydrophobic content

Hydrophobically associating block copolymers of polyacrylamide/styrene with a high hydrophobe content were synthesized using micellar copolymerization under various conditions of surfactant and initiator concentrations with the objective of determining the conditions that produce optimum solution properties for enhanced oil recovery. Solubilities, aqueous solution viscosities and interfacial properties with air and oil of the copolymers were investigated. The influence of salt on the solution properties was also studied. Nature of hydrophobic sites and onset of hydrophobic association were studied by measuring the fluorescence of pyrene in polymer solutions. Optimum solution properties were obtained for copolymers synthesized under conditions of high surfactant and initiator concentrations. The copolymers displayed substantial thickening properties at low concentrations with enhanced thickening in the presence of salt. The interfacial tensions of the aqueous solutions with n-decane and air were also reduced. Interfacial properties were slightly sensitive to salt concentration. The copolymer solutions showed shear and temperature thinning behaviors typical of polymer solutions.     

Synthesis and Thermothickening Behavior of Graft Copolymers Based on poly(N,N-Diethylacrylamide-co-N,N-Dismethylacrylamide) Side Chains

A new type of thermothickening graft copolymer was synthesized through free radical copolymerization and grafting onto technique in aqueous solution. Their molecular structure combines a hydrophilic backbone based on poly(acrylicacid-co-2-acrylamido-2-methylpropane sulfonic acid and thermosensitive side chains based on N,N-diethylacrylamide and N,N-dimethylacrylamide (DMAA). The lower critical solution temperature of poly(N,N-diethylacrylamide) was increased easily by copolymerizing with hydrophilic monomers DMAA. The results demonstrate that the polymers in aqueous solution exhibit a significant increase in viscosity with the temperature rising and their thermothickening behavior is related to various physicochemical parameters such as the concentration of the polymer, shear rate, chemical composition of side chains, salt concentration, and pH value.     

New amphoteric graft copolymers of sodium carboxymethyl cellulose with acrylamide and dimethylaminoethyl methacrylate: Aqueous solution properties

The solubility and viscosity properties of new amphoteric graft copolymers of sodium carboxymethyl cellulose with acrylamide and dimethylaminoethyl methacrylate in aqueous solutions were investigated by turbidimetry and viscometry experiments. The factors investigated include the pH of the medium, the composition of the graft copolymer, the concentration and type of added salt, temperature, aging time, and the addition of organic solvent. Unlike conventional copolymers, these graft copolymers have unique solution behavior due to the presence of both acidic and basic groups along the macromolecular backbone. In addition, their solution properties are closely related to their conformations and are partially controlled by the net electrical charge and the ionic strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 305–310, 2000     

新型温敏改性丙烯酰胺共聚物的性能研究

以2,2,3,4,4,4-六氟甲基丙烯酸酯(AF6)和丙烯酸辛烷基酚聚氧乙烯酯(OPA7)为共聚单体改性聚丙烯酰胺(PAM),得到P(AM-AF6)、P(AM-OPA7)和P(AM-OPA7-AF6)三种共聚物,其中P(AM-OPA7-AF6)溶液表现良好的热增稠性。采用可见分光光度计、动态光散射(DLS)和荧光分光光度计研究了三种共聚物分子在溶液中的相互作用。结果表明:P(AM-AF6)和P(AM-OPA7)溶液在30～85℃未产生疏水缔合,高温增稠现象不明显。对于P(AM-OPA7-AF6)聚合物,单体AF6与OPA7中的氟碳链与聚乙烯醚链在升温过程中的协同作用极大地影响了聚合物分子的自组装行为,诱发了溶液-凝胶转变行为,明显提高了其盐溶液表观黏度。     

Solution behavior of graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches: effect of structure and composition

Summary The effect of structure and composition of poly(methyl methacrylate) (PMMA) main chain and poly(propylene oxide-b-ethylene oxide) (PPO-b-PEO) graft chain on solution behavior was evaluated. Separated samples of homopolymers were also analysed to provide comparisons. The solutions were prepared by dissolving the sample in selective mixtures of tetrahydrofuran (THF) and hexane. The polymer solutions were submitted to viscometric measurements as function of the solvent composition. The ratio of ethylene oxide/propylene oxide (EO/PO) units determines the modification in molecular conformation of the (PPO-b-PEO) block copolymers as function of the solvent composition. The macromolecular structure is the most important factor on the graft copolymers behavior. The structure in which ethylene oxide is linked to the main chain provides higher interaction between graft copolymers and solvent (THF/hexane).     

Modification of cellulose acetate reverse osmosis membranes by radiation grafting

Large excesses of a chain transfer agent, carbon tetrachloride, were introduced to a recipe for the mutual radiation grafting of styrene to cellulose acetate film. The effect of the carbon tetrachloride on the molecular characteristics as well as the reverse osmosis and time dependent mechanical properties of resulting graft copolymers was determined. Extremely short side chains were generated as a consequence of the high concentrations of chain transfer agent and the composite results further suggest that the morphology of the grafted films is best described as “destructured” or internally plasticized consequent to grafting in the presence of CCl₄. Reverse osmosis fluxes increased with percent graft; salt rejection was high and unaffected by per cent graft up to 40% graft; and the tensile creep under wet conditions was significantly retarded by the grafting. These effects were shown to accrue from grafting per se by control experiments involving α-methylstyrene which will not propagate to form a polymer under these conditions. These results are compared and contrasted with earlier work on grafting in the absence of CCl₄ where long side chains of polystyrene were generated resulting in a structuring of the polymer involving domains of polystyrene-rich material and domains of cellulose acetate rich polymer.     

Graft copolymers of starch with mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate

Mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate (DMAEMA·HNO₃) have been graft polymerized onto unmodified wheat starch with ferrous ammonium sulfate–hydrogen peroxide initiation. Graft polymerizations were carried out with both unswollen starch granules and granules that had been swollen by heating in water to 60°C. Ungrafted synthetic polymers were removed from graft copolymers by cold-water extraction and were characterized by their M?_n and DMAEMA·HNO₃ content. Graft copolymers were characterized with respect to per cent add-on, M?_n and DMAEMA·HNO₃ content of grafted polymer, and grafting frequency. Ungrafted synthetic polymers contained a mole percentage of DMAEMA·HNO₃ equal to or greater than that present in the initial monomer mixtures; whereas in most grafted polymers the mole-% DMAEMA·HNO₃ in the grafted branches was less than that in the starting monomers. At all monomer ratios examined, polymer grafted to swollen starch granules contained a higher percentage of DMAEMA·HNO₃ then polymer grafted to unswollen starch. The influence of starch granule swelling on the molecular weight and frequency of grafted branches was correlated with the composition of the initial monomer mixture. It was determined that the effect of granule swelling on graft copolymer structure would be minimal when 25–30 mole-% DMAEMA·HNO₃ was used. In an acetonitrile–water solvent system, reactions with 20 and 50 mole-% DMAEMA·HNO₃ produced graft copolymers with less DMAEMA·HNO₃ in grafted branches than corresponding graft polymerizations run in water. The flocculation of 3% aqueous suspensions of diatomaceous silica was examined with selected starch graft copolymers.     

Novel developments in the multidimensional characterization of segmented copolymers

Controlled radical polymerization (CRP) provides the polymer chemist with the ability to produce tailor-made polymers with controlled molar masses, molar mass distributions, chemical compositions and macromolecular architectures. Segmented copolymers can be synthesized having polymer segments arranged in a linear fashion (linear block copolymers), however, polymer segments can also be attached to pre-synthesized macromolecules or to multifunctional core molecules to produce branched (graft) copolymers, polymer stars or dendrimers. Although there are many ways to control the chain growth and the architecture of the target macromolecules, side reactions cannot be completely avoided. Accordingly, even with CRP, obtained products exhibit chemical composition and topology distributions along with the molar mass distribution.     

Synthesis and aqueous solution properties of hydrophobically modified graft copolymer of sodium carboxymethylcellulose with acrylamide and dimethyloctyl(2‐methacryloxyethyl)ammonium bromide

The hydrophobically modified water‐soluble graft copolymer of sodium carboxymethylcellulose with acrylamide and dimethyloctyl(2‐methacryloxyethyl)ammonium bromide has been synthesized using potassium persulfate and dimethylaminoethyl methacrylate as initiators in aqueous solution. The structure and composition of the graft copolymer were characterized by infrared spectrum and elementary analysis. Molecular weight was determined by gel permeation chromatography. The solubility and viscosity of the graft copolymers in aqueous solution were investigated, as a function of copolymer concentration, added salt, temperature, shear rate, and surfactant. In addition, the intermolecular hydrophobic association in aqueous solutions in the presence of added salt and surfactant was demonstrated through the retention time from gel permeation chromatography measurement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 537–542, 2000