Anionic Polymerization of 4-Allyldimethylsilylstyrene: Versatile Polymer Scaffolds for Post-Polymerization Modification
Shivani P. Wadgaonkar, Manfred Wagner, Axel H. E. Müller, Holger Frey
Abstract
A facile synthesis using a Grignard reaction was employed to prepare the silicon containing functional monomer 4-allyldimethylsilylstyrene (4ADSS). Detailed studies regarding the living nature of anionic polymerization of 4ADSS and its polymerization via the styrene vinyl bond in cyclohexane at room temperature were conducted, and P4ADSS samples with M n up to 80 kg mol –1 were accessible. This evidences that the 4ADSS structure disables undesired proton transfer side reactions, as known for the carbon-based analogue functional monomer 4-but-3-enyl-styrene. Real-time 1 H NMR kinetics of the statistical copolymerization of 4ADSS with styrene ( r 4ADSS = 3.55; r S = 0.047) revealed a remarkable gradient microstructure in the resulting copolymers. Based on this observation, a library of well-defined gradient copolymers P(4ADSS- co -S) with M n in the range of 5–50 kg mol –1 was synthesized, varying 4ADSS content. A comprehensive discussion regarding the glass transition temperatures ( T g ) of the synthesized homo- and copolymers is presented. Furthermore, thiol–ene click reactions at the pendant allyl moiety of P(4ADSS- co -S) were explored to introduce functional groups. Likewise, P(4ADSS- co -S) copolymers were subjected to hydrosilylation reactions, and the impact of the introduced siloxane moieties on the glass transition of the resulting copolymers is presented. Both thiol–ene reactions as well as hydrosilylation of the P(4ADSS- co -S) copolymers proceeded quantitatively. Consequently, copolymerization of 4ADSS provides access to a wide range of polystyrene-based functional materials with specific applications using versatile post-polymerization chemistry.