Poly[(styrene-co-p-methylstyrene)-b-isobutylene-b-(styrene-co-p-methylstyrene)] Triblock Copolymers. 1. Synthesis and Characterization
Poly[(styrene-co-p-methylstyrene)-b-isobutylene-b-(styrene-co-p-methylstyrene)] Triblock Copolymers. 1. Synthesis and Characterization
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聚[(苯乙烯-对甲基苯乙烯)-b-异丁烯-b-(苯乙烯-对甲基苯乙烯)]三嵌段共聚物。
DOI：
10.1016/j.polymer.2004.05.003
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发表时间：
2004
期刊：
影响因子：
4.6
通讯作者：
K. Mauritz
中科院分区：
文献类型：
--
作者：
Stacy J. Taylor;R. Storey;J. Kopchick;K. Mauritz
研究了聚异丁烯(PIB)基三嵌段共聚物的合成，其末端嵌段含有苯乙烯和对甲基苯乙烯(PMSt)重复单元，以尽量减少在末端嵌段聚合过程中发生在苯乙烯重复单元上4位的链偶联反应。通过改变苯乙烯和PMSt的投料比进行了模型末端嵌段共聚反应，1H核磁共振分析表明，在低转化率的情况下，PMSt在活性链端的加入略有优势。然而，DSC显示了随着PMSt含量的增加而增加的单一玻璃化转变温度，证实了微观结构中没有块状。采用不同投料比合成了Poly[(styrene-co-pMSt)-b-isobutylene-b-(styrene-co-pMSt)]三嵌段共聚物。PIB引发的末端嵌段共聚反应比TMPC1引发的模型末端嵌段共聚反应具有更长的反应时间和更大的一级曲线。这是由于嵌段共聚中PIB中心嵌段提供的非极性局部反应介质较多，导致电离平衡常数较低，终止程度较高所致。凝胶渗透色谱(GPC)分析表明，随着原料中PMSt浓度的增加，代表链状偶联产物的高分子量峰降低。
The synthesis of poly(isobutylene) (PIB)-based triblock copolymers having copolymer end blocks containing styrene and p-methylstyrene (pMSt) repeat units was investigated in an attempt to minimize chain-coupling reactions that occur at the 4-position on styrene repeat units during end block polymerization. Model end block copolymerizations using varying feed ratios of styrene and pMSt were conducted, and it was determined by1H NMR analysis that the addition of pMSt to the living chain end was favored slightly at low conversion. However, DSC revealed a single Tgthat increased with increasing pMSt content verifying the absence of blockiness in the microstructure. Poly[(styrene-co-pMSt)-b-isobutylene-b-(styrene-co-pMSt)] triblock copolymers were synthesized using varying feed ratios of styrene and pMSt. The rate of end block propagation increased with increasing pMSt in the feed, and the end block copolymerizations initiated by PIB displayed longer reaction times and more curvature in their first order plots than did the model end block copolymerizations initiated by TMPCl. This effect was attributed to lower ionization equilibrium constant and higher degree of termination caused by the more non-polar local reaction medium provided by the PIB center blocks in block copolymerization. GPC analysis of the final BCPs revealed a decrease in a high molecular weight peak representing the chain-coupled product as the concentration of pMSt in the feed was increased.