Simultaneous coating of silica particles by two diblock copolymers.

ABSTRACT

Silica particles have been coated by two diblock copolymers, P1 and P2, through a one-pot reaction, and the resultant particles were characterized. The P1 and P2 used were synthesized by anionic polymerization and denote PIPSMA-b-PFOEMA and PIPSMA-b-PtBA, respectively. Here PIPSMA, PFOEMA, and PtBA correspond individually to poly[3-(triisopropyloxysilyl)propyl methacrylate], poly(perfluorooctylethyl methacrylate), and poly(tert-butyl acrylate). Catalyzed by HCl, the PIPSMA blocks of P1 and P2 co-condensed onto the surface of the same silica particles, exposing the PtBA and PFOEMA blocks. The relative amounts of grafted P1 and P2 could be tuned by changing the P1 to P2 weight ratio and were quantified by thermogravimetric analysis. The vertical segregation of the PFOEMA and PtBA chains could also be adjusted. Casting a dispersion of the coated particles in a solvent selective for either PFOEMA or PtBA onto glass plates or silicon wafers yielded films consisting of bumpy silica particles whose surfaces were enriched by the polymer that was soluble in the casting solvent. Particulate coatings with tunable surface wetting properties were obtained by changing either the proportion of grafted P1 and P2 or the casting solvent for coated silica. When a silica dispersion in perfluoromethylcychohexane (C(7)F(14)) was cast, films of coated silica that had P1 weight fractions of 25, 50, and 75% were all superhydrophobic because the particle surfaces were enriched by PFOEMA, which was selectively soluble in C(7)F(14).