End-Functionalization of Syndiotactic Polystyrene and Preparations of Syndiotactic Polystyrene Based Stereoregular Diblock Copolymers via the Vinylsilane-Induced Selective Chain Transfer Reaction

• Main Authors: Hao-jen Hsiao, 蕭浩然
• Other Authors: Jing-Cherng Tsai
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/43793821960946194780

碩士 === 國立中正大學 === 化學工程所 === 97 === Syndiotactic polystyrene (sPS) possesses many good properties, including a high melting temperature, a high glass transition temperature, high crystallinity, good hardness and a fast crystallization rate, to be used as a high performance engineering plastic. However, the high crystallinity of sPS also results in brittleness and low impact strength which may substantially limit the commercial applications of sPS. As the impact strength of sPS has been demonstrated to improve by linking or grafting with other polymer block, this research is aiming for the development of new methods that can lead to the successfully preparation of sPS-based diblock copolymers. By conducting the syndiospecific 4-chlorostyrene and 4-fluorostyrene polymerization using dimethylphenylvinylsilane (DMPhVS) as the chain transfer agent, vinylsilane end-capped syndiotactic poly-4-chlorostyrene (sP4CS) and vinylsilane end-capped syndiotactic poly-4-fluorostyrene (sP4FS) can be selectively produced by using Cp*Ti(OMe)3/MAO as the catalyst. The resulting end-capped polymers contain the uniform vinylsilane end group; thus, can be used as the end-functionalized stereoregular prepolymer for conducting subsequent postpolymerization for the preparation of sP4CS- and sP4FS-based stereoregular diblock copolymers. . Accordingly, we have successfully prepared the sP4CS-b-PLLA by conducting ring opening polymerization (ROP) of DL-lactide using the hydroxy-capped sP4CS as the macroinitiator. The sP4FS-b-aPS, on the other hand, can be selectively produced by conducting living radical (ATRP) polymerization of styrene using α-bromoisobutyl end-capped sP4FS as the macroinitiator. The diblock copolymers prepared by these new synthetic methods have been found to possess well-defined chemical structures (uniform block lengths and narrow ranges of molecular weight distribution) to be used in the self-assembly studies for displaying consistent nanomorphologies as revealed by TEM analyses