A Nonconventional Approach toward Multihydroxy Functional Polystyrenes Relying on a Simple Grignard Reagent

Abstract

Capitalizing on the inertness of styrene toward Grignard reagents, 4-vinylphenylmagnesium bromide was utilized for the rapid and convenient preparation of the protected monomer 2,2-dimethyl-4-(4-vinylbenzyl)-1,3-dioxolane (DMVBDO), avoiding the use of catalysts and painstaking purification protocols. Well-defined homopolymers, statistical copolymers, and block copolymers with styrene (S) as a comonomer were prepared in THF at −78 °C via carbanionic living polymerization. The overall molecular weights ranged from 4.5 to 68.9 kg mol–1 with low dispersities (Đ 1.04–1.15). Copolymers were synthesized with styrene feed ratios (Xfeed) from 15 to 95 mol % with glass transition temperatures (Tg) between 46 and 91 °C. Whereas polystyryllithium served as an excellent macroinitiator for the preparation of the block copolymer PS0.5-b-P(DMVBDO)0.5, the inverse block order, i.e., synthesis of P(DMVBDO)0.5-b-PS0.5, yielded a bimodal molecular weight distribution (MWD) with increased dispersity, which is ascribed to slow crossover. Rapid deprotection of both homo- and copolymers to release two hydroxyl groups per DMVBDO unit was achieved via acidic hydrolysis. The deprotected block copolymer PS0.5-b-P(VPPDO)0.5 showed phase separation, indicated by two Tg values (68 and 86 °C). Homogeneous brush copolymers of the type P(S85-co-VPPDO5)-g-PLLA and P(S85-co-VPPDO6)-g-PEO were demonstrated by using quantitative “grafting from” with l-lactide and ethylene oxide, respectively. The brush-like copolymers were obtained in quantitative yields while maintaining monodisperse MWD.