Compositions, devices, and methods are disclosed for the modification of polymer surfaces with coatings having a dispersion of silicone polymer and hydrophobic silica. The surface coatings provide the polymer surface with high hydrophobicity, as well as increased resistance to biofouling with proteinaceous material. The polymer surfaces can be particularly useful in microfluidic devices and methods that involve the contacting of the covalently modified polymer surfaces with emulsions of aqueous droplets containing biological macromolecules within an oil carrier phase.