Synergistic control of breath figures on Styrene-Butadiene-Styrene films by poly-2-ethyl-2-oxazoline capped CaCl2 loaded mesoporous silica particles

Abstract

The addition of hydrophilic components (CaCl2, poly-2-ethyl-2-oxazoline (PEOX) or mesoporous silica particles (MSP)) into Styrene-Butadiene-Styrene (SBS)/chloroform solution was shown to affect the resulting breath figure patterns in terms of pore size, pore shape and order. Honeycomb-patterned porous SBS polymer films were prepared by adding 30 wt% PEOX capped, CaCl2 loaded mesoporous silica particles into SBS solution. The long-range order observed with a pore diameter of ∼3.6 µm in the breath figure pattern at RT and 50–70% RH was attributed to the synergistic contributions of each component. CaCl2 promotes the condensation of water vapor and the nucleation of many water droplets on the polymer solution. When localized in a uniformly swollen layer of PEOX around MSP, easier nucleation together with stabilization of water droplets by MSP and PEOX leads to hexagonally-ordered breath figures. The results demonstrate the addition of hydrophilic components as an easy tool to tune breath figure patterns at relatively low humidity and their synergistic contributions.