PEB/MMA-AN悬浮接枝共聚反应机理

研究了乙烯-1-丁烯共聚物(PEB)弹性体与甲基丙烯酸甲酯(MMA)-丙烯腈(AN)悬浮接枝共聚反应行为及接枝共聚产物对SAN树脂增韧作用随反应时间的变化规律, 用凝胶渗透色谱法和傅里叶变换红外光谱法对接枝共聚产物进行了表征, 分析了接枝共聚反应机理, 推算了接枝链分子量. 结果表明, 体系首先发生链增长自由基向PEB转移终止形成非接枝共聚物(MAN_L)和PEB大分子自由基引发单体共聚形成接枝链(g-MAN)的反应, 接枝反应结束后体系发生明显的非接枝共聚形成非接枝共聚物(MAN_H)的反应; MAN_L的分子量低于g-MAN的分子量, 而g-MAN的分子量明显低于MAN_H的分子量; 在接枝共聚过程中发生已接枝和未接枝PEB断链并随机再接生成多嵌段共聚物的副反应; 在反应初期, 接枝链的AN单元含量接近于非接枝共聚物的AN单元含量, 在反应中后期前者远低于后者.     

碳链接枝共聚物——Ⅲ.聚丙烯酰胺的均相氧化及其与苯乙烯接枝共聚反应

不久前我们曾报导了聚丙烯酰胺的水溶液在室温或55℃时有可能与过氧化氢发生均相氧化反应,形成聚丙烯酰胺大分子过氧化物.这种水溶性的聚丙烯酰胺大分子过氧化物可引发烯类单体的接枝共聚,得到相应的碳链接枝共聚物。利用这种简便的接枝方法不仅可以合成一系列具有综合性能的接枝共聚物新品种,而且对大分子过氧化物引发烯类单体接枝共聚反应历程的研究也具有一定意义。     

共聚理论进展

凡由两种或多种单体构成链节的高聚物称为共聚物,而合成此类聚合物的过程叫做共聚反应。按聚合反应机制可分为自由基型和离子型两种。根据生成的共聚物链结构序列的不同,则可分为无规共聚、交替共聚、嵌段共聚和接枝共聚。本世纪初发现了共聚现象。早期主要研究了异戊二烯和丁二烯,丁二烯与苯乙烯和丙烯腈,以及一系列烯类和双烯类单体的共聚反应,并且得到了一些有价     

聚苯乙烯大分子单体与醋酸乙烯酯接枝共聚物的合成及表征

<正> 用大分子单体与小分子单体共聚是七十年代初才出现的合成接枝共聚物的一种新方法。通过共聚合反应而不是接枝反应同时形成主干及支链。这种接枝共聚物由于形成支链的大分子单体是预先合成的,其分子量分布较窄,又可调节控制,所以合成的接枝共聚物支链长短比较均一,副反应较少,链结构比较明确,因此也易于表征。     

大分子单体及其规整接枝共聚物

论述了通过活性阴离子聚合、活性阳离子聚合、基团转移聚合、自由基聚合、缩聚等途径合成各种大分子单体,论讨了大分子单体的表征,并结合自己的工作综合介绍近年来大分子单体共聚的进展及其规整接枝共聚物的纯化和特性。     

甲壳素/壳聚糖接枝共聚反应

综述了近年来甲壳素/壳聚糖接枝共聚的研究进展。以不同单体分类,分别综述了壳聚糖与小分子乙烯基单体、大分子聚乙二醇单体、聚乳酸单体、环糊精、树状大分子接枝的研究,并介绍了新的接枝技术——生物催化接枝共聚,以及接枝壳聚糖衍生物的应用。     

纤维素与苯乙烯-丙烯腈共聚用单体的接枝共聚

研究了以高锰酸钾为引发剂,苯乙烯-丙烯腈共聚用单体与纤维素的接枝共聚。讨论了影响接枝共聚反应的一些参数,反应规律和接枝共聚物的结构及性质。实验表明,在以水为介质的反应体系中,接枝共聚反应可顺利进行。     

PU大分子单体水溶液性质

双亲聚合物一般由亲水和亲油 2种链段构成 ,有嵌段型[1,2 ] 和接枝型[3 ] 2种 ,其中通过大分子单体法合成双亲接枝聚合物备受关注[4] 。如以亲水性大分子单体和亲油性小分子单体共聚 ,大分子单体构成共聚物主链上支链 ,具有较大活动性 ,亲水效能高。采用对氯甲基苯乙烯[5] 或甲基丙烯酰氯[6] 与聚氧化乙烯大分子的一端相反应 ,可得到亲水性大分子单体 ,但其分子量及结构变化有限。本文采用常规条件 ,合成了嵌段式水溶性聚氨酯大分子单体 ,其分子量较大 ,共聚接枝的支链较长。利用该大分子单体具有非离子高分子表面活性剂的性质 ,采用无皂乳…     

“活”的α-甲基苯乙烯共聚物:聚合反应新化学和材料工程新技术

高于临界聚合反应温度时,α-甲基苯乙烯(AMS)单体和其聚合物处于聚合-解聚平衡.基于AMS聚合物在受热时可裂解生成大分子链自由基的特性,提出了含AMS结构单元的共聚物是一种"活"的,可作为大分子自由基引发剂的概念,并通过实验对AMS共聚物的引发性能和应用进行了研究.首先,合成了AMS与(甲基)丙烯酸酯类单体、丙烯酸、苯乙烯和马来酸酐等的共聚物.然后以上述共聚物为大分子引发剂,在90℃引发(甲基)丙烯酸酯类单体和苯乙烯等的本体聚合、溶液聚合和乳液聚合,得到了嵌段共聚物.用ESR谱证明了AMS的共聚物在加热时能裂解生成以碳原子为中心的大分子链自由基.此外,在聚合物的熔融共混中,AMS分解产生的大分子链自由基通过偶合反应形成接枝链,原位生成相容剂.AMS共聚物还可以对碳纳米管及无机粒子进行表面原位接枝改性.AMS共聚物是一类无小分子残留的绿色自由基引发剂,可以用于低成本制备两嵌段共聚物,也可以用于聚合物的熔融共混增容.     

阴离子型含氟两亲接枝共聚物的合成及其胶束化行为研究

以聚乙二醇甲醚甲基丙烯酸酯(MPEGMA)为大分子单体,甲基丙烯酸六氟丁酯(HFMA)、对苯乙烯磺酸钠(NaSS)为共聚单体,采用大分子单体接枝共聚法,制备了一种阴离子型含氟两亲接枝共聚物P( HFMA-co-NaSS) -g-PEG.利用FTIR、1H-NMR和19F-NMR对共聚物的分子结构进行了表征.表面张力法测...     

Surface modification of polyamide-6: graft copolymerization of vinyl monomers onto polyamide-6 and thermal analysis of the graft copolymers

Graft copolymerization of vinyl monomers onto polyamide-6 using radical initiation has been investigated. Two monomers were used: methacrylic acid and acrylic acid. The initiators selected included hydrogen peroxide, benzoyl peroxide and azobisisobutyronitrile. The extent of graft copolymerization depends on the concentrations and identity of the initiator and monomer and the time and temperature of the reaction. The graft copolymers were not soluble in solvents that will dissolve the starting material; definitive proof for the formation of the graft copolymers was obtained from infrared spectroscopy. Thermogravimetric analysis was performed on the graft copolymers and it was found that the presence of the acid invariably accelerated the degradation of the polyamide. © 1998 John Wiley & Sons, Ltd.     

醋酸乙烯酯与1-(2-叔丁基过氧异丙基)-3-异丙烯基苯(D120)的共聚行为研究

共聚合;竞聚率;过氧化物;醋酸乙烯酯与1-(2-叔丁基过氧异丙基)-3-异丙烯基苯(D120)的共聚行为研究     

Interconvertible Living Radical and Cationic Polymerization through Reversible Activation of Dormant Species with Dual Activity

The polymerization of vinyl monomers generally requires the selection of an appropriate single intermediate, whereas in copolymerization, the selection of the comonomer is limited by the intermediate. Herein, we propose interconvertible dual active species that can connect comonomers through different mechanisms to produce specific comonomer sequences in a single polymer chain. More specifically, two different stimuli, that is, a radical initiator and a Lewis acid, are used to activate the common dormant C? SC(S)Z group into radical and cationic species, thereby inducing interconvertible radical and cationic copolymerization of acrylate and vinyl ether to produce a copolymer chain that consists of radically and cationically polymerized segments. The dual reversible activation provides control over molecular weights and multiblock copolymers with tunable segment lengths.     

The 25th anniversary of catalytic chain transfer

The transfer of hydrogen from a free radical to an olefin is catalyzed by some cobalt chelates. This reaction, when used in free-radical polymerization, can be called catalytic chain transfer (CCT) to a monomer. It allows the manufacture of oligomers that have defined molecular weights and are useful for a variety of applications. Because all the oligomers are getting terminal double bonds, they can behave as macromers. These macromers give rise to the formation of diblock and graft copolymers, telechelic polymers that have the same or different functional groups depending on the conditions and origins of the comonomers. The catalyst structure–property relation is discussed. Redox properties affect the CCT and provide additional leverage in controlling polymerization processes. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1753–1766, 2000     

Acrylic thermoplastic elastomers and comb-shaped poly(methyl methacrylate) via the macromonomer technique

Comb-shaped poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PnBuA) grafted with PMMA were prepared by radical copolymerization of ω-methacryloyl-PMMA with MMA and nBuA, respectively. The comb-shaped PMMA is characterized with respect to radius of gyration by using gel permeation chromatography equipped with a multi-angle laser light scattering detector. The radical copolymerization of the macromonomer with nBuA in toluene follows complex kinetics. The dependence of the relative reactivity of the macromonomer on absolute concentration and on the ratio of comonomers may be explained by preferential solvation of comonomers by segments of their own kind (“bootstrap effect”) or even micelle formation. However, there is no clear evidence for the formation of micelles in toluene. In contrast, NMR studies show micelle formation in the preferential solvent dimethyl sulfoxide. The graft copolymers are transparent thermoplastic elastomers. Phase separation is demonstrated by differential scanning calorimetry and morphological studies.     

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     

聚苯乙烯大单体与乙酸乙烯酯的共聚及其接枝共聚物的表征

研究了聚苯乙烯大单体与乙酸乙烯酯的溶液聚合,结果表明,接枝效率随引发剂用量、聚合温度及小单体与大单体的投料比的增加而增加,随大单体的分子量增加而减少,而随单体浓度的变化呈现一最大值。共聚过程中大单体的转化率开始较小单体的增加快,后期变慢。用萃取法纯化的接枝共聚物经GPC、IR、~1H-NMR及PGC等表征,并算得平均接枝数为4—7。透射电镜表明接枝共聚物中存在微观相分离。     

Et(Ind)_2ZrCl_2/MAO催化乙烯和ω-对甲苯基-α-烯烃共聚合的研究

使用Et(Ind)2ZrCl2/MAO催化剂催化乙烯和3种ω-对甲苯基-α-烯烃(对甲苯基-1-丙烯,4-对甲苯基-1-丁烯,6-对甲苯基-1-己烯)共聚,主要研究了共单体加入量对催化剂活性和所得共聚物性能的影响.4-对甲苯基-1-丁烯表现出最好的共聚性能.使用1H-NMR、13C-NMR、GPC和DSC对共聚物进行了表征.     

FREE-RADICAL-INITIATED COPOLYMERIZATION OF 2-CHLOROSTYRENE, 4-CHLOROSTYRENE,AND 2,6-DICHLOROSTYRENE WITH MALEIC ANHYDRIDE

The title copolymers have been prepared by the free-radical-initiated copolymerization of 2-chlorostyrene (2-ClSt), 4-chlorostyrene (4-ClSt) and 2,6-dichlorostyrene (2,6-DClSt) with maleic anhydride (MAn) in toluene at 65°C. Copolymers of chlorinated styrenes with MAn prepared under different monomer-to-monomer ratios in the feed have alternating composition. In all cases, the mixture of comonomers forms charge-transfer complex monomers (CTC). The initial rate of copolymerization increases with the increase of electron donors in the comonomer feed, and the highest rates were at the equimolar ratios of comonomers in the feed. The thermal stability of the polymers was measured by thermogravimetric analysis in nitrogen. Homopolymers decompose by a one-step mechanism, while copolymers are more thermostable and decompose by a two-step mechanism. Glass transition temperatures (T_gs) of homopolymers are lower than T_gs of copolymers. The number and weight average molecular weights of chlorinated copolymers are higher than those of the corresponding homopolymers.     

聚苯乙烯大单体与乙酸乙烯酯的共聚及其接枝共聚物的表征

 研究了聚苯乙烯大单体与乙酸乙烯酯的溶液聚合,结果表明,接枝效率随引发剂用量、聚合温度及小单体与大单体的投料比的增加而增加,随大单体的分子量增加而减少,而随单体浓度的变化呈现一最大值。共聚过程中大单体的转化率开始较小单体的增加快,后期变慢。用萃取法纯化的接枝共聚物经GPC、IR、¹H-NMR及PGC等表征,并算得平均接枝数为4—7。透射电镜表明接枝共聚物中存在微观相分离。