Stable, aqueous emulsion copolymers with controllable siloxane crosslinking functionality are provided. These copolymers are prepared by a free radical and cationic initiated emulsion polymerization of at least one free radical initiatable monomer, at least one linear polysiloxane precursor monomer, and at least one polysilane or polysiloxane precursor monomer having both free radical polymerizable and siloxane crosslinking functionality. The copolymers are useful in curable coatings, paints, caulks, adhesives, non-woven and ceramic compositions and as modifiers, processing aids and additives in thermoplastics, cements and asphalts.