Synthesis of hyperbranched-linear star block copolymers by atom transfer radical polymerization of styrene using hyperbranched poly(siloxysilane) (HBPS) macroinitiator

摘要

Hyperbranched-linear star block copolymers, hyperbranched poly(siloxysilane)-block-polystyrene (HBPS-b-PSt), were prepared by atom transfer radical polymerization (ATRP) of styrene in xylene, using bromoester-terminated HBPS (HBPS-Br (P3), M-n = 7500, M-w/ M-n = 1.76) as a macroinitiator. The number-average molecular weights of the obtained polymers (M-n) were in the range of 21,800-60,000 and molecular weight distributions were unimodal throughout the reaction (M-w/M-n = 1.28-1.40). These polymers showed 5 wt.% decomposition temperature (T-d5) over 300 degrees C. The DSC thermograms of the resulting polymers indicated two glass transition temperatures (T-g). The T-g of HBPS segment shifted to higher value while the T-g of PSt segment shifted to lower value compared with those of the homopolymers. Preliminary physical characterization related to the solution viscosity of the resulting block copolymers is also reported.