A composite composition is disclosed that comprises the reaction product of a mixture of a styrenic polymer, as defined herein, a polar component having nucleophilic functional groups, and from 0.5 to 10 wt % of a compatibilizer having the formula: R.sub.y(I)-(styrene).sub.n-[(styrene).sub.m(X)].sub.p--I(R.sub.y) wherein: R is the residue of a nitroxide used to regulate the polymerization of the compatibilizer; I is the residue of a radical initiator used to initiate polymerization of the compatibilizer; n is an integer from 50 to 750; m is an integer from 0 to 10; p is an integer from 1 to 50; and y is an integer from 0 to 1; and X is any polymerized monomeric moiety having at least one functional group capable of reacting with the nucleophilic functional groups present in the polar component of the composite at the temperature at which the composite components are mixed.