Structured hydrophilic domains on silicone elastomers

The controlled generation of hydrophilic structures within hydrophobic polymers can be challenging. Very few examples of such structures have been described for silicones. We now report that such structures can be encoded in the air-contacting layer of a silicone elastomer by the formation of silica domains from tetraethoxysilane, optionally in the presence of poly(ethylene glycol) (PEG), using a surface active aminopropylsilicone catalyst and moisture cure. The control of the relative modulus at the upper versus lower layers and the degree and type of hydrophilic structuring requires control over the efficiency of delivery of water to the core of the pre-elastomer, which is facilitated by the surface active catalyst and may additionally be manipulated by the addition of PEG.