Synthesis Of Star-Shaped Polymers And Heteroarm Star-Shaped Polymers

This dissertation consists of the following two parts: In the first part, star-shaped polystyrenes have been successfully synthesized by coupling reaction between multifunctional core molecules and hydroxyl terminal polystyrene in the presence of 1, 3-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine at room temperature. Several systems were investigated: pyromellitic dianhydride (PMDA) with narrow molecular weight distribution hydroxyl-terminated polystyrene obtained via atom transfer radical polymerization with 2-hydroxyethyl-2'-methyl-2'-bromopropinate as initiator; PMDA with hydroxyl-terminated polystyrene obtained via conventional free radical polymerization with 2-mercaptoethanol as chain transfer agent; narrow molecular weight distribution alternating copolymerization of maleic anhydride (MAn) and styrene via RAFT process with hydroxyl-terminated polystyrene obtained via ATRP; Styrene/MAn alternating copolymer obtained by conventional free radical copolymerization with hydroxyl-terminated polystyrene prepared by conventional free radical polymerization. The formation of star-shaped polystyrenes was confirmed by H NMR and gel-permeation chromatography equipped with a light-scattering detector.In the second part, heteroarm star-shaped polymers were synthesized by conventional free radical polymerization in two steps by the use of polyfunctional chain transfer agent. In the first step, free radical polymerization of methyl methacrylate was carried out in the presence of a polyfunctional chain transfer agent, pentaerythritol-tetrakis(3-mercaptopropinate). At appropriate monomer conversions, two-arm PMMA having two residual thiol groups at the chain center or three-arm PMMA having one residual thiol group at the core were obtained. In the second step, free radical polymerization of styrene was carried out using PMMAs obtained above macro-chain transfer agent. When styrene conversion was lower than 30%, heteroarm star-shaped polymers, (PMMA)(PS) and (PMMA)(PS), were obtained successfully.