Pyridine-containing block copolymer/silica core-shell nanoparticles for one-step preparation of superhydrophobic surfaces

Two poly(4-vinylpyridine)-b-polystyrene diblock copolymer/silica core-shell nanoparticles (P4VP-b-PS/SiO2 NPs) are developed in this work. Confirmed by DLS analysis and TEM observation, one comprises a SiO2 core surrounded by a P4VP-b-PS shell and the other comprises a P4VP-b-PS core surrounded by a SiO2 shell, which is facilely prepared by the in situ hydrolysis of tetraethyl orthosilicate (TEOS) using cationic P4VP-b-PS micelles obtained in a THF-H2C2O4 (aq, 0.1 mol L-1) mixture and a DMF-H2C2O4 (aq, 0.01 mol L-1) mixture as template, respectively. The SCA, CAH, SA and SEM measurements reveal that one-step deposition of P4VP-b-PS/SiO2 NPs with SiO2 cores formed at a high level of TEOS creates a superhydrophobic surface with an SCA of 160 degrees, a CAH of 2 degrees and an SA of around 4 degrees originating from the formation of a typical micro-nanoscale binary structure (MNBS). For the NPs with SiO2 cores formed at a low level of TEOS, the superhydrophobicity with a SCA of 151 degrees, CAH of 3 degrees and SA of around 5 degrees can be induced by the transition of the surface microstructure from an uneven and discontinuous MNBS, created by a one-step deposition process, to the coexistence of MNBS and a nanoscale structure (NS) after annealing with toluene for 30 min. In contrast, one-step deposition of P4VP-b-PS/SiO2 NPs with P4VP-b-PS cores and SiO2 shells usually results in the inhomogeneous precipitation of SiO2 from bulk P4VP-b-PS along with the production of micro-cracks, with which is impossible to achieve surface superhydrophobicity.