Tunable wettability of hierarchical structured coatings derived from one-step synthesized raspberry-like poly(styrene-acrylic acid) particles

A facile one-step method to fabricate hierarchical structured coatings whose wettability could be easily tuned from hydrophilic (water contact angle, 9.3°) to superhydrophobic (water contact angle, 154.2°) by controlling the assembly temperature without any specialized equipment or additional modification is reported. The building blocks for the coatings, hierarchically raspberry-like poly(styrene-acrylic acid) (P(S-AA)) particles with 10 nm corona particles on the core, were produced via a one-step soap-free emulsion polymerization process accompanied by phase separation. The morphology and roughness of the raspberry-like particles can be conveniently regulated by adjusting the amount of S, AA and divinylbenzene (DVB). The chemical composition, crosslinking degree, hierarchical structure and roughness of the raspberry-like particles have significant influence on the wettability of the coatings. The transition of the wettability was attributed to a thermodynamic-driven process that hydrophobic components of the particles migrate toward the surface of the coatings and a decrease of the roughness of the hierarchical structure that was a result of softening and fusing of the particles at temperatures above the T_g of the copolymers.