Functionalized copolymers of isoolefins and conjugated diolefins, methods of preparing said copolymers, and their use as compatibilizers are disclosed. The diolefin monomer units of the co-polymer are modified at the C-C double bond along the backbone of the copolymer to include an oxygen containing functional group such as epoxide, ester or alcohol. The functionalized copolymers improve the wettabilty of a non-hydrophilic surface towards hydrophilic polymer and allows for the formation of homogenous layers of the hydrophilic polymers. In particular, the spreading of a hydrophilic polymer on a non-hydrophilic substrate is facilitated by applying the co-polymers as an interfacial layer between the two incompatible materials. The resulting coated substrates exhibit resistance to protein adsorption and cell growth after grafting. The co-polymers are especially suited in the coating of biomedical devices where a high degree of uniformity of the coated surface is required.
