Reversible Addition-Fragmentation Chain Transfer (RAFT) Free Radical Polymerization In Mesoporous Materials

Currently,reversible addition fragmentation chain transfer radical polymerization(RAFT)in the field of living polymerization has attaracted more interests owing to its unique features.However,there are few reports on the RAFT polymerization inside the pore structure of mesoporous material and the study of the effect of the pore on the reaction confination.In this dissertation,different mesoporous materials,such as SBA-15,MCM-41,MCM-48 and modified ones are selected as the“microreactor”for RAFT solution polymerization inside the channel of them.The researches contents and main conclusions are as follows:(1)Ethyl xanthate ethyl propionate was used as chain transfer agent for RAFT polymerization of methyl methacrylate(MMA).The PMMA-CTA was employed for the preparation of PMMA-b-PS block copolymer by adding the second monomer styrene(St).The PMMA and PMMA-b-PS block copolymer were characterized by Fourier Transform Infrared Spectroscopy(FT-IR),hydrogen nuclear magnetic resonance(~1H NMR),gel permeation chromatography(GPC),thermogravimetry analysis(TGA)and differential scanning calorimetry(DSC).The results indicated that the PMMA macromolecular chain transfer had copolymerized with the second monomer St and the expected block copolymer was formed.The PMMA-b-PS block copolymer possessed a high molecular weight and a wide molecular weight distribution.The initial decomposition temperature of the PMMA-b-PS copolymer increased significantly,while the glass transition temperature(Tg)was in the range between that of PMMA and PS.(2)Different mesoporous materials(rod like SBA-15,spherical SBA-15,MCM-41,MCM-48 and mesoporous material modified by silane coupling agent KH550)were used as microreactor,RAFT solution polymerization of MMA was carried out inside the channels of them.Nitrogen adsorption and desorption,GPC,FT-IR,TG,scanning electron microscope(SEM),~1H NMR and other test methods were used to characterize the composites and PMMA inside the pores.The results showed that the modified mesoporous materials and composites maintained the original morphology structure,and the specific surface area,pore size,and pore volume all decrease.Compared with conventional RAFT polymerized product(C-PMMA),the molecular weight of the PMMA inside the pores was several times or even more than ten times higher than that of C-PMMA,while the molecular weight distribution broadened;the proportion of syndiotactic was significantly decreased,and the initial thermal decomposition temperature is increased,especially the initial decomposition temperature of the PMMA obtained from modified mesoporous materials increased of 80-100 C.(3)Different pore sizes of the SBA-15 were used as"microreactor"and RAFT solution polymerization of MMA was performed inside the pores.Nitrogen adsorption and desorption,GPC,FT-IR,TG,SEM,~1H NMR and other test methods were used to characterize the composites and the PMMA inside the pores.The results showed that the specific surface area,pore size,pore volume and ordered degree of the composite decreased.Compared with the conventional RAFT polymerized product(C-PMMA),the initial decomposition temperature and Tg of the PMMA inner product increased;with the increase of the pore size,the molecular weight increased significantly,and molecular weight distribution was between 1.34-1.55,the syndiotactic proportion of polymers increased.(4)The SBA-15 was modified with KH560,KH570,and KH151 as a microreactor and RAFT solution polymerization of MMA was performed inside the pores.Nitrogen adsorption and desorption,GPC,FT-IR,TG and other test methods were used to characterize the composites and PMMA inside the pores.The results showed that the specific surface area,pore volume and pore size of the composite material and the modified M-SBA-15 all reduced.Compared with the conventional RAFT polymerized prouduct C-PMMA,the initial thermal decomposition temperature of the PMMA obtained from the pore polymerization increased,the molecular weight increased significantly,and the syndiotactic proportion increased also.KH151 modified SBA-15produced the least level of PMMA,but the obtained PMMA exhibited the highest molecular weight and thermal decomposition temperature.