Nanostructured Films of Oppositely Charged Domains from Self-Assembled Block Copolymers

The exploration of poly­(tert-butyl methacrylate)-block-poly­(4-vinylpyridine), PtBMA-b-P4VP, as a precursor material for the creation of nanostructured films with oppositely charged domains is reported. Thin films of hexagonally packed P4VP cylinders were self-assembled perpendicular to the surface and subsequently treated with bromoethane vapor at various times to quaternize pyridinyl nitrogens. The PtBMA matrix was then partially hydrolyzed to poly­(methacrylic acid), PMAA, through HCl vapor treatment followed by neutralization by brief submersion in KOH solution. Under optimal treatment conditions, atomic force microscopy and contact angle measurements confirm that the film morphologies remain intact and become more hydrophilic. Time-of-flight secondary ion mass spectrometry confirms the presence and location of specific anions and cations within each domain throughout the block copolymer film and corroborates successful ionization during each treatment step. These results bolster the viability of PtBMA-b-P4VP as a suitable material for creating self-assembled nanostructures bearing oppositely charged domains under relatively facile conditions and open the door to future investigations for their potential application in charged mosaic membranes.