Abstract: Materials having structure (1), wherein R and R1 may be the same or different and each independently represents an alkyl or aryl group, X may be hydrogen or a C1 to C20 alkyl group which may be branched or linear and wherein the aromatic ring substituent joined to polymer B is positioned meta or para to the aromatic ring substituent joined to polymer A and, wherein polymer A is a non-polar polymer formed by metallocene catalysis and polymer B is a polymer formed by radical catalysis of a polar monomer are used as polymer additives particularly to improve the compatibility of mixtures of polymers.