Simple Strategies to Manipulate Hydrophilic Domains in Silicones

Hydrophilic silicone polymers offer advantageous properties in a variety of applications. However, it is not always straightforward to control the placement of hydrophilic domains in a hydrophobic silicone elastomer. A facile method for the preparation of poly(ethylene oxide)(PEO)-modified PDMS elastomers is described. Hydrosilane rich elastomers are fabricated by adding poly(hydromethylsiloxane) to a standard addition cure elastomer formula. After curing the elastomer, the silicones can be modified using hydrosilylation with mono- and di-allyl pol(ethylene oxide) of varying molecular weights to give PEO-rich silicone surfaces. The efficiency of the grafting process, as measured by PEO on the surface, depends both on molecular weight and functionality of the PEO. By contrast, when the allyl functional PEO is added directly to the elastomer preparation (co-cure), silicone elastomers with internal PEO domains are formed: SiH rich polymers present preferentially at the external interface.