Relationship between the Co-Continuous Morphology of Immiscible Polymer Blends and the Structure of an In Situ Formed Graft Copolymer.

In order to get stable co-continuous morphology in immiscible polymer blends, besides reducing the interfacial tension, the compatibilizer should not only promote the formation of flat interface between different phases, but also not hinder the coalescence of the dispersed phase. Herein, the relationship between the morphology of the compatibilized polystyrene/nylon 6/styrene-maleic anhydride (PS/PA6/SMA) immiscible polymer blends and the structures of the in-situ formed SMA-g-PA6 graft copolymers as well as the processing conditions are studied. Two kinds of SMA are used: SMA28 (28 wt.% MAH) and SMA11 (11 wt.% MAH). After melt blending with PA6, the in-situ formed copolymer SMA28-g-PA6 has on average of four PA6 side chains, while that of SMA11-g-PA6 has only one. Dissipative particle dynamics simulation results indicate that both SMA28-g-PA6 copolymer and PS/PA6/SMA28 blends tend to form co-continuous structure, while those related to SMA11 intend to form sea-island morphologies. These results are correct only at relatively low rotor speed (60 rpm). When the rotor speed is higher (105 rpm), sea-island morphologies are obtained in SMA28 systems, while that for SMA11 ones are co-continuous. This indicates that higher shear stress can elongate the minor phase domains to form flat interfaces, while the SMA28-g-PA6 copolymers can be pulled out from the interface.