Surface modification of gels and elastomers is an important but often challenging task. Here we demonstrate a new and versatile method that can modify the surface of elastomers and gels, using PDMS as a model system. A PDMS gel containing hexane solution with a reactive monomer (tri-mesoyl chloride, or TMC) was prepared and placed within an aqueous solution containing another reactive monomer (m-phenylenediamine, or MPD). During this process, MPD diffused into the swollen PDMS network and reacted with TMC to form polyamide (PA)-like materials near PDMS surfaces. After solvent evaporation, the PDMS surface formed a series of hierarchical wrinkles and folds, due to the formation of a much stiffer PDMS/PA surface layer that has low degree of swelling. The properties of the modified surfaces including chemical composition, morphology, wettability and mechanical properties were systematically characterized.<br/>Compared with other surface modification methods such as plasma or chemical etching, the infiltration-polymerization method yields a much more compliant surface layer that can sustain extremely high surface wrinkling/folding without fracture. The surface features can be tuned by controlling the infiltration polymerization process including reaction time, solution formulation, as well as by the degree of swelling and crosslinking density of the PDMS. Furthermore, the use of elastomeric substrates allows mechanical manipulation such as pre-strain during any stage of the process, as well as surface patterning of the gels before the process, to achieve complex surface morphologies.

Modifying PDMS surface using infiltration interfacial polymerization

253rd National Meeting (2017)

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