Radical Polymerization of Isotactic and Syndiotactic PMMA Macromonomers

将含有苯乙烯基团的聚甲基丙烯酸甲酯(PMMA)活性阴离子与对乙烯基溴反应，合成了高等规度(iso-)和间规度(syn-)聚甲基丙烯酸甲酯(PMMA)大分子单体，并用自由基引发剂考察了它们的聚合反应。异PMMA大单体的聚合速率(Rp)略高于合成大单体。在与苯乙烯的自由基共聚反应中，也观察到了类似的反应活性的规整性依赖关系。终止速率常数(K_T)可由传播自由基电子自旋共振信号的衰减直接确定。为了确定大分子单体链上的引发剂链段数目(N)和引发剂效率(F)，用~2H核磁共振波谱分析了过氚后得到的大分子单体的AIBN。由R_p、k_t和f估算了…的增长速率常数(K_P)。k_t和k_p值均远小于苯乙烯聚合的k_t和k_t的降低大分子单体的增加比k_p的降低更为明显，异大分子单体的k_p和k_t值大于合成大单体的相应值。结果表明，异大分子链的链段迁移率高于聚甲基丙烯酸甲酯的链段迁移率，导致k_p和k_t值较大。异大分子单体和合成大分子单体在氯仿、甲苯和二甲基亚砜(DMSO)中的共聚反应也证实了异大分子单体具有较高的反应活性。然而，Rp和异大分子单体对Synn-one的相对反应性依氯仿&Gt；甲苯&Gt；DMSO的顺序递减，这与立体络合物形成能力的递减顺序相同，这表明某些特定的相互作用降低了大分子单体的迁移率，缩小了它们之间的反应活性差异。GPC-LALLS测定发现，聚(异大分子单体)在氯仿中的体积大于聚(Synn-大分子单体)，这与线性PMMA的情况相似。还考察了立体规则大分子单体与线形PMMA在固体中的立体络合物的形成。从立体络合物中有效地合成了异大分子单体和大分子单体的共聚物，而这些大分子单体的均聚物的混合物则不能。较少

Highly isotactic (iso-) and syndiotactic (syn-) poly (methyl methacrylate) (PMMA) macromonomers having a styrene group were prepared by the reaction of the corresponding PMMA living anions with p-vinylbenzyl bromide and their polymerizations were examined by using radical initiator. The rate of polymerization (R_p) of iso-PMMA macromonomer was slightly higher than that of syn-macromonomer. A similar tacticity dependence of the reactivity was also observed in the radical copolymerization with styrene. Termination rate constant (k_t) could be directly determined from the decay of ESR signals of propagating radicals. To determine the number of initiator fragment in a polymacromonomer chain (N) and initiator efficiency (f), polymacromonomers obtained with perdeuterated were AIBN analyzed by ^2H NMR spectroscopy. Propagation rate constant (k_p was estimated from R_p, k_t and f. Both the k_t and k_p values were much smaller than those for styrene polymerization, and the decrease of k_t of th … More e macromonomer was much more evident than the decrease of k_p. The k_p and k_t values for iso-macromonomer were larger than the corresponding values for the syn-one. The result suggests that the higher segmental mobility of iso-PMMA chain than that of syn-PMMA chain brings about the larger k_p and k_t values.Copolymerization of iso-and syn-macromonmers in chloroform, toluene and dimethyl sulfoxide (DMSO) also confirmed higher reactivity of the iso-macromonomer. However, R_p and the relative reactivity of the iso-macromonomer to syn-one decreased depending on the solvent in the order of chloroform > toluene > DMSO, which is the same as the order of decrease in capability of stereocomplex formation, suggesting that some specific interaction lowers mobility of macromonomer and diminishes the difference in their reactivities.Poly (iso-macromonomer) was found to have larger volume in chloroform than poly (syn-macromonomer) as determined by GPC-LALLS, similarly to the case of linear PMMAs. Stereocomplex formation between stereoregular polymacromonomers and linear PMMAs in solid was also examined. Copolymers of iso-and syn-macromonomers from stereocomplex effectively though a mixture of the homopolymers of these macromonomers did not. Less