Novel Well-defined Polystyrene-block-Poly(lactide-co-glycolide) Block Copolymers

Abstract

A facile preparation of polystyrene-block-poly(lactide-co-glycolide) PS-b-PLGA block copolymers was reported in detail. Well-defined PS-b-PLGA block copolymers were successfully obtained via living anionic polymerization and ring-opening polymerization. First, hydroxyl-terminated linear polystyrenes were prepared by living anionic polymerization. The resulting polymers were used as macroinitiators for ring-opening copolymerization of lactide and glycolide in the presence of the 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst in dichloromethane at ambient temperature. Transesterification and formation of DBU-initiated polymers were minimized by optimizing the catalyst concentration. Three block copolymers were synthesized in various molecular weights from 5000 g/mol to 33600 g/mol with low polydispersity. The formation of well-defined PS-b-PLGA block copolymers was followed by nuclear magnetic resonance spectroscopy and size-exclusion chromatography. Thermal properties of the block copolymers were investigated by thermal gravimetric analysis and differential scanning calorimetry. The morphology of the block copolymers was investigated using small-angle X-ray scattering in the bulk and via grazing incidence small-angle X-ray scattering as well as atomic force microscopy in thin film demonstrating organized nanostructures with uniform domain sizes. Overall, this manuscript describes an expanded polymer toolbox for PLGA-based polymers for next-generation lithography applications.