Syndiospecific living block copolymerization of styrenic monomers containing functional groups, and preparation of syndiotactic poly{(4-hydroxystyrene)-block-[(4-methylstyrene)-co-(4-hydroxystyrene)]}

At -25°C, the sequential block copolymerizations of 4-(tert-butyldimethylsilyloxy)styrene (TBDMSS) and 4-methylstyrene (4MS) were investigated by using a syndiospecific living polymerization catalyst system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe3), trioctylaluminum (AlOct3) and tris(pentafluorophenyl)borane (B(C6F5)3). The number average molecular weight. (Mn) of the poly (TBDMSS)s increased linearly with increasing the polymer yield up to almost 100 wt.-% consumption of TBDMSS used as 1st monomer. The Mnvalue of the polymer after the 2nd monomer (4MS) addition continued to increase proportionally to the polymer yield. The molecular weight distributions (MWDs) of the polymers remained constant at around 1.05-1.18 over the entire course of block copolymerizations. It was concluded that the block copolymerizations of TBDMSS and 4MS with the Cp*TiMe3/B(C6F5)3/ AlOct3 catalytic system proceeded with a high block efficiency. The 13C NMR analysis clarified that the block copolymers obtained in this work has highly syndiotactic structure. By the deprotection reaction of silyl group with conc. hydrochloric acid (HCl), syndiotactic poly{(4-hydroxystyrene)-block-[4(4-methylstyrene)-co-(4-hydroxystyrene)]} (poly[HOST-b-(4MS-co-HOST)]) was successfully prepared.