1,3-二烯基-1,1,3,3-四甲基二硅氧烷/苯乙烯共聚合的环化率与竞聚率

对１３０℃下１，３ 二烯基 １，１，３，３ 四甲基二硅氧烷（ＤＶＤＳ）／苯乙烯（Ｓｔ）的溶液环化共聚合动力学进行了研究．根据低转化率（＜１０％）的共聚物组成及环状结构比例，通过参数估计方法，求得环化率与竞聚率，分别为ｒ１＝０１０２、ｒ２＝３４８、ｒｃ＝００２１０、Ｋｃ＝３８１ｍｏｌ／Ｌ、Ｋ′ｃ＝０３８９ｍｏｌ／Ｌ，同时得到它们９５％置信概率的联合置信区间及其交互影响的联合置信区间．表明ＤＶＤＳ的反应活性较Ｓｔ低，其非环状结构自由基具有较强的分子内环化反应能力；环的位阻效应使环状结构ＤＶＤＳ自由基的活性低于其非环状结构自由基．

CYCLIZATION COEFFICIENTS AND REACTIVITY RATIOS FOR 1,3-DIVINYL-1,1,3,3-TETRAMETHYLDISILOXANE/ STYRENE COPOLYMERIZATION

The solution cyclocopolymerization of 1,3 divinyl 1,1,3,3-tetramethyldisiloxane(DVDS) with styrene(St) at 130℃ was investigated.The overall conversions for all copolymerization runs were controlled less than 10%.The copolymer compositions and percentages of DVDS forming the ring structures in the copolymers were determined by 1H and 29Si NMR,respectively.Using the nonlinear parameter estimation,the cyclization coefficients and reactivity ratios were calculated as r1=0 102,r 2=34 8,r c=0 0210,Kc=3 81mol/L,and K′ c=0 389mol/L.The 95% reliability intervals for the estimated kinetic constants were given also.The experimental results indicate that DVDS was less active than St,and the DVDS uncyclized radicals were easy to form the cyclic structures via the intramolecular cyclization.Due to the steric hindrance,the activities of DVDS cyclized radicals were lower than its uncyclized ones.