Stable polymer brushes with effectively varied grafting density synthesized from highly crosslinked random copolymer thin films

Abstract

We demonstrate the synthesis of poly(methyl methacrylate) (PMMA) and poly(styrene-<i>b</i>-methyl methacrylate) (P(S-<i>b</i>-MMA)) brushes on crosslinked random copolymer thin films, compositionally varied poly(styrene-<i>r</i>-glycidyl methacrylate) (P(S-<i>r</i>-GMA)), which can be further functionalized with a molecule featuring an initiator group upon crosslinking to form highly stable thin films. With careful optimizations, PMMA brushes were successfully grown from the surfaces of initiator functionalized P(S-<i>r</i>-GMA) <i>via</i> surface-initiated atom transfer radical polymerization. The grafting densities of the PMMA and P(S-<i>b</i>-MMA) brushes were effectively controlled to be in different density regimes by controlling the composition of P(S-<i>r</i>-GMA) and post-crosslinking functionalization methods. Synthesized BCP brushes were stable upon repetitive washing and thermal annealing processes even at high grafting density, highlighting that the outstanding stability of crosslinked P(S-<i>r</i>-GMA) thin films enables close examination of the morphology of thermally annealed P(S-<i>b</i>-MMA) brushes in different grafting density regimes.