Reactive blending of functional PS and PMMA: Interfacial behavior of in situ formed graft copolymers

omega -Isocyanate PMMA, alpha -anhydride PMMA, and PS-co-PSNH2 have been pr epared by atom transfer radical polymerization (ATRP) with controlled molec ular weights (10(4) and 3.5 x 10(4)) and low polydispersity (1.2). They hav e been used as precursors of PS-g-PMMA copolymers and let to react in the m elt (170 degreesC, for 10 min) under moderate shear rate. The well-controll ed molecular characteristics of these precursors are a substantial advantag e to study the effect of the kinetics of the interfacial reaction on the ph ase morphology. When the grafting reaction is fast (NH2/anhydride pair) and low molecular weight chains are used, the interfacial reaction is quasi-co mplete and a nanophase morphology is observed, whereas limited reaction and formation of microphases are observed in all the other cases. A high react ion yield requires not only that the functional groups are highly mutually reactive but also that the interface is anytime made available to the funct ional polymers for the reaction to progress. Then, a nanophase morphology m ay be observed, which is that of the copolymer formed by the interfacial re action. A low reaction yield is dictated by either a slow interfacial react ion or a slow diffusion of the copolymer away from the interface. In the la tter case, the phases formed by the unreacted precursors are stabilized by the copolymer which resides at the interface.