Synthesis of Block Copolymer Brush by RAFT and Click Chemistry and Its Self-Assembly as a Thin Film

Abstract

A well-defined block copolymer brush poly(glycidyl methacrylate)-graft-(poly(methyl methacrylate)-block- poly(oligo(ethylene glycol) methyl ether methacrylate)) (PGMA-g-(PMMA-b-POEGMA)) is synthesized via grafting from an approach based on a combination of click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. The resulting block copolymer brushes were characterized by ¹H-NMR and size exclusion chromatography (SEC). The self-assembly of the block copolymer brush was then investigated under selective solvent conditions in three systems: THF/water, THF/CH₃OH, and DMSO/CHCl₃. PGMA-g-(PMMA-b-POEGMA) was found to self-assemble into spherical micelle structures as analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of the particles was much smaller in THF/CH₃OH and DMSO/CHCl₃ as compared with the THF/water system. Thin film of block copolymer brushes with tunable surface properties was then prepared by the spin-coating technique. The thickness of the thin film was confirmed by scanning electron microscopy (SEM). Atom force microscopy (AFM) analysis revealed a spherical morphology when the block copolymer brush was treated with poor solvents for the backbone and hydrophobic side chains. The contact angle measurements were used to confirm the surface rearrangements of the block copolymer brushes.

Keywords: block copolymer brush; click chemistry; self-assembly; thin film.