RAFT polymerization of MMA in channels of different mesoporous materials

Abstract

Reversible addition fragmentation transfer (RAFT) polymerization is of key signi cance for its suitability for most monomer and well-studied reaction mechanism. Herein, a serial of mesoporous silica (MS) materials, including rod-liked and spherical SBA-15, spherical MCM-41, and MCM-48, were successfully synthesized and modi ed by silane coupling agent γ-aminopropyltriethoxysilane (KH550). The modi ed MS was utilized as a microreactor for reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) using a xanthate as a chain transfer agent and AIBN as an initiator. Note that modi ed MS had lower speci c surface area and pore volume while maintained the original morphological structure. Owing to the con nement effects, poly(methyl methacrylate) (PMMA) prepared from internal mesoporous channels featured with higher molecule weight and initial thermal decomposition temperature than these from conventional RAFT polymerization. More importantly, the PMMA obtained from the spherical SBA-15 and modi ed MCM-48 exhibited the highest molecule weight.This work provided a novel approach to design of polymer microstructure for a wider application, such as in drug release. AR), ammonia water (NH 3 •H 2 O, 25-28%), tetraethyl orthosilicate (TEOS, AR), hydro uoric acid (HF, ≥ 40%) hydrochloric acid (HCl,(36)(37)(38), and tetrahydrofuran (THF, AR) were all purchased from Xilong Science and Technology Co., Ltd. MMA was treated with 10% aqueous NaOH solution for three times to remove the inhibitor, then washed with distilled water to be neutral, dried with anhydrous CaCl 2 , and distilled under reduced pressure. Anhydrous ethanol (AR) was purchased from Guangdong Guanghua Technology Co., Ltd. Azodiisobutyronitrile (AIBN, AR), purchased from Tianjin Guangfu Fine Chemical Research Institute, was used after recrystallization from absolute ethanol. Potassium ethyl xanthate (AR) and ethyl 2-bromopropionate (AR) were purchased from Aladdin Industrial Corporation (Shanghai, China) and used directly. γ-aminopropyltriethoxysilane (KH550, CP) was purchased from Nanjing Xiangfei Chemical Research Institute. Ethyl xanthate ethyl propionate was synthesized according to the reported work [24]. All other chemicals were used as received without further puri cation.