Study On The Phase Behavior Of Poly (Methyl Methacrylate)/poly (Stvrene-Coacrylonitrile) Blends Filled With Polymer Grafted Graphene

The significant discrepancy in the dispersion and distribution of nanoparticles in polymer blend matrix may be induced by different chemical composition and microstructure of nanoparticles.The selective distribution of nanoparticles in the blend matrix may affect the morphology/structure of blend matrix and further the ultimate properties of nanocomposites.Hence,surface grafting modification of nanoparticles by introducing new small molecules or macromolecules can change the surface chemical property of nanoparticles to improve the compatibility between them and polymer matrix,which may control the dispersion and distribution of nanoparticles in the blend matrix and further optimize the performance of nanocomposites.In this work,three kinds of surface grafting-modified graphene nanosheetswere prepared,including poly(methyl methacrylate)grafted reduced graphene oxide(PMMA-g-RGO),poly(methyl methacrylate-co-styrene)grafted RGO(P(MMA-co-St)-g-RGO)and poly(styrene-co-maleic anhydride)grafted GO(SMA-g-GO).The modified nanosheets were introduced into PMMA/poly(styrene-co-acrylonitrile)(SAN)blends with the lower critical solution temperature(LCST).The selective distribution of such modified nanosheets in PMMA/SAN blend matrix,the phase behavior and conductive properties of PMMA/SAN/modified nanosheets nanocomposites were invesitigated by transmission electron microscopy(TEM),small angle laser light scattering(SALLS)and real-time online digital picoammeter.The grafting ratios with different surface grafting strategies are different.Here,the grating ratio of P(MMA-co-St)-g-RGO was the highest and that of SMA-g-GO is the lowest.P(MMA-co-St)-g-RGO and PMMA-g-RGO nanosheets were both dispersed uniformly in the homogeneous blend matrix.With phase separation of the blend matrix,such two modified nanosheets preferentially migrated to the SAN-rich phase and showed remarkably little aggregation subjected to thermal annealing.Surface grafting of PMMA-g-RGO might inhibit the aggregation of nanosheets in the blend matrix and weaken the retardation effect of nanosheets on the morphology evolution of the blend matrix.Furthermore,the percolation behavior of dynamic resistivity for ternary nanocomposites was attributed to the formation of PMMA-g-RGO conductive network in the SAN-rich phase.The activation energy of conductive pathway formation was closer to the activation energy of flow for PMMA than that of SAN.Due to high surface grafting ratio of P(MMA-co-St)-g-RGO nanosheets,their conductivity decreased and such nanosheets hardly formed the effective conductive pathway during thermal annealing without the emergence of dynamic resistance percolation behavior.Furthermore,P(MMA-co-St)-g-RGO nanosheets might retard the concentration fluctuation of blend matrix at the early stage of phase separation to a certain extent Due to low surface grafting ratio of SMA-g-GO nanosheets,the interaction between the nanosheets could be hardly screened and such nanosheets aggregated severely in the homogeneous or heterogeneous blend matrix,resulting in no formation of conductive pathway.