A prerequisite to broaden the performance spectrum of plastics has motivated much interest in blending different types of polymers to obtain materials with enhanced mechanical properties. In order to tailor properties for specific applications, the compatibilization of immiscible polymer blends is of paramount importance. An effective compatibilizer can be produced in situ by the reaction between co-reactive functional groups in the blend constituents during blending process. Reactive compatibilization, potentially presents a simple and cost-efficient route to the morphology control in immiscible blends, which may be achieved through various types of functional group interactions. In situ formed compatibilizers are obtained by blending suitable functionalized polymers capable of enhancing specific interactions and/or chemical reactions.