线形与星形端烃羧基聚二甲基硅氧烷的合成与表征

摘要

利用三步法合成了一系列具有不同臂数的线形和多臂星形端烃羧基聚二甲基硅氧烷(PDMS-MAAx,x=1,2,3,4):首先,以Si-H数量不同的含氢封头剂分别与八甲基环四硅氧烷(D4)开环聚合,制得线形和多臂星形端氢基聚二甲基硅氧烷(PDMS-Hx)；继而与甲基丙烯酸甲酯(MMA)进行硅氢加成反应,制得酯基封端的聚二甲基硅氧烷(PDMS-MMAx)；最后将酯基在碱性条件下水解,制得PDMS-MAAx.采用FT’-IR和1H NMR对三个合成阶段的反应产物进行了跟踪分析,确认了各步产物的结构,并讨论了PDMS-MMAx和PDMS-MAAx的合成条件对产物结构的影响,在此基础上优化了PDMS-MAAx的制备工艺,确定了PDMS-MMAx的最佳合成条件为:Si-H与MMA的量之比为1.0∶1.2、反应温度70～80℃、催化剂摩尔浓度20×10-6～60×10-6、反应时间5 h；PDMS-MMAx水解制备PDMS-MAAx的最佳条件为:NaOH水溶液中NaOH的质量分数为20％、NaOH水溶液以及乙醇的用量分别为PDMS-MMAx 体积的3倍和1倍.%A three-step procedure was developed for synthesizing a series of linear and star-shaped carboxyl-terminated polydimethylsiloxane,i.e.,PDMS-MAAx (x =1,2,3,4).First,the hydrogen-terminated PDMS with virous arms (PDMS-Hx) were prepared based on the ring-opening polymerization of octamethylcyclotetrasiloxane (D4) ; then,methyl methacrylate (MMA) was reacted with PDMS-Hx to prepare ester terminated PDMS (PDMS-MMAx) ; finally,the terminal ester group was transformed to terminal carboxyl acid based on the hydrolysis reaction of ester under alkaline condition to obtain carboxyl acid terminated PDMS,i.e.,PDMS-MAAx.FT-IR and 1 H NMR were employed to confirm the structure of the product in each step of reactions and the effects of synthetic conditions on the structure of the products were discussed.Also,the optimal conditions for the preparation of PDMS-MMAx were with a mole ratio of Si-H and MMA of 1.0∶ 1.2,and a catalyst molality of 20 × 10-6 ～60 × 10-6 at 70 ～80℃ for 5 hours.The optimal conditions for the preparation of PDMS-MAAx were that 20％ mass fraction of NaOH in NaOH solution,and the volume of the NaOH solution and ethanol was threefold and one time of the PDMS-MMAx.