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 degrees) to superhydrophobic (water contact angle, 154.2 degrees) 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.