Stereoregular Diblock Copolymers of Syndiotactic Polystyrene Derivatives and Polylactide: Syntheses and Self-Assembled Nanostructures

Abstract

Structurally well-defined stereoregular diblock copolymers, syndiotactic poly(4-methylstyrene)-b-poly(L-lactide) (sPMS-b-PLLA), were prepared by the controlled ring-opening polymerization of an aluminum alkoxide end-capped sPMS macroinitiator with l-lactide. The aluminum alkoxide end-capped sPMS macroinitiator was generated via the reaction between hydroxyl-capped sPMS and triethylaluminum. The hydroxyl-capped sPMS was prepared from the hydroboration of ethenyl-capped sPMS. The ethenyl-capped sPMS was generated by the desilylation of dimethylphenylvinylsilane-capped sPMS prepared via a unique vinylsilane-inducing selective chain transfer reaction during the syndiospecific polymerization of 4-methylstyrene conducted in the presence of dimethylphenylvinylsilane using Cp*Ti(OMe)3/MAO as catalyst. The proposed synthetic method can be used for the preparation of a broad variety of end-functionalized syndiotactic polystyrene derivatives (syndiotactic polystyrenes) end-capped with various end groups and facilitates the synthesis of syndiotactic polystyrenes-based stereoregular BCPs. The method offers effective control over the stereoregularity of polystyrenes and facilitates linking between blocks to provide stereoregular BCPs, which are capable of generating well-ordered nanostructures resulting from the self-assembly of stereoregular BCPs, as evidenced by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM).