Polymer dispersions of polymers derived from silicone macromers and ethylenically unsaturated monomers are capable of incorporating large amounts of chemically bonded macromer, when the silicone macromer and part of the unsaturated monomer are polymerized in aqueous medium as an initial charge with an oil soluble initiator, and the remaining monomers are fed in and polymerized using a water soluble initiator. The dispersions may be dried to form water redispersible polymer powders.