A Generalized Method for the Preparation of Neutral Brushes from Homopolymer Mixtures

We demonstrate a new, generalized approach for the formation of neutral surfaces that uses a ternary blend of hydroxyl-terminated homopolymers A-OH and B-OH and a low MW A-$b$-B block copolymer. The presence of the block copolymer effectively homogenizes the A/B homopolymer mixture before the homopolymers are grafted onto the substrate, thereby preventing macroscopic phase separation of the homopolymer mixture, and maintaining chemical neutrality over the length scales necessary for the self-assembly of block copolymer microdomains. The grafting ratios of the two homopolymers were varied simply by changing the blend ratios. Neutral compositions for P(S$-b-$MMA) and P(S-$b$-2VP) were located using this binary homopolymer mixture strategy.