Multi-liquid repellent, fluorine-free, heat stable SLIPS via layer-by-layer assembly

Abstract

Slippery liquid-infused porous surfaces (SLIPS) are an emerging class of bio-inspired materials attracting researchers due to their good anti-fouling, anti-icing, and self-cleaning performance. The fluorinated lubricants which are used in the preparation of multi-liquid repellent SLIPS are not suitable for practical applications because of the lubricant losses by evaporation and water drop cloaking and also they cause environmental and health problems. In this study, layer-by-layer (LbL) assembly technique via a capping approach is used to obtain PDMS-based SLIPSs. Amino terminated PDMS was used as a homofunctional polymer layer and three different copolymers of anhydride [poly(ethylene-alt-maleic anhydride) PEMA, poly(isobutylene-alt-maleic anhydride) PIMA and poly(maleic anhydride-alt-1-octadecene) PMAO] were used as the capping layers to give LbL layers having advancing contact angles between 115° and 120° with the change of the type of anhydride copolymer used and the constituent concentration. Silicone oil was used as the lubricant giving a fluorine-free LbL-SLIPS having a contact angle hysteresis as low as 5–6° repelling water and various other liquids such as glycerol, ketchup and soy sauce by preserving the low contact angle hysteresis for long durations. Moreover, LbL-SLIPS samples also had good heat resistance (to 80 °C for 8 days) and chemical stability against acids and bases and were durable under the flow of continuous water droplets for a period of 4 h without any damage to SLIPS properties. The best performing LbL-SLIPS sample was prepared using the PEMA capping layer where the decrease in silicone oil thickness and increase in contact angle hystresis were found to be lowest under continuous water droplet flow after 4 h.