Rapid photochromic nanopatterns from block copolymers

Abstract

Photochromic nanopatterns were produced from the self-assembly of poly(methyl methacrylate)-b-poly(n-butylacrylate) (PMMA-b-PBA) block copolymers incorporating a naphthopyran photochromic dye. The PMMA-b-PBA block copolymers were synthesized by reversible addition fragmentation chain transfer polymerization with a photochromic dye (9-acryloyloxy-[3,3-bis(4-methoxyphenyl)]-3H-naphtho[2,1-b]pyran) attached to the PBA block (PMMA-b-P(BA-co-NA)). The very low glass transition temperature of the poly(n-butyl acrylate) (PBA) block allows for rapid decolouration of the naphthopyran dye, whilst the PMMA matrix permits the macroscopic rigidity of the photochromic film to be maintained. The resulting films exhibit the fastest rate of colour switching reported to date for a naphthopyran polymeric film. Furthermore, the PMMA-b-PBA block copolymer exhibits microphase separation in nanodomains of controlled and regular morphology, thus allowing the confinement of the photochromic dye in well-controlled nanostructures. This feature allowed us to design polymeric films exhibiting precisely defined photochromic nanopatterns.