Structure Characterization And Rheological Behavior Of Polymer/Polymer Based Nano Composites

Three kinds of composite nanoparticles were prepared by seededemulsion polymerization, which are high crosslinking poly(methylmethacrylate)/polystyrene (PMMA(HC)/PS), high crosslinking poly(meth-ylmethacrylate)/low crosslinking poly(butylacrylate)/polystyrene PMMA-(HC)/PBA(LC)/PS and high cross-linking poly(methylmethacrylate)/poly(methylmethacrylate-styrene) / polystyrene (PMMA(HC) /P(MMA-St)/PS). The morphology and structure of composite nanoparticles werecharacterized by dynamic light scattering and transmittance electronicmicroscope, and chemical components of composite particles wereinvestigated by column chromatogram, thin film chromatogram, GPC,FTIR, and NMR. These composite particles have the same nano-sizedPMMA(HC) core, thick linear PS shells and different interfacial structure.Furthermore, the corresponding bulk composites were prepared bymolding or extruding. The morphology of these bulk composites,especially the effects of temperature field and shear field on the dispersionstability of PMMA(HC) nanoparticles in PS matrix, were investigated.Then the dynamic rheologic behavior of bulk composite materials werealso studied.The results show that PMMA(HC)/PS composite nanoparticles havea snowman-like morphology because the interfacial tension between PMMA and PS is large and the compatibility is not good. However, PMMA(HC) nanoparticles can keep a stable dispersion in bulk composite during molten quiescent condition or shear field. The reason maybe that there are some grafting PS on PMMA(HC) nanoparticles.As to PMMA(HC)/PBA(LC)/PS composite nanoparticles, due to the existence of low crosslinked PBA(LC) on surfaces of nanoparticles, there are more PS grafted on the surface of PMMA(HC) nanoparticles. Therefore, composite particles have core-shell structure, and PMMA(HC) nanoparticles have better dispersion stability in PS matrix.The interfacial tension between PMMA(HC) and PS is effectively reduced due to the presence of interfacial gradient copolymer, PMMA(HC) /P(MMA-St)/PS composite nanoparticles have perfect core-shell structure. However, the dispersion of PMMA(HC) nanoparticles in the bulk composite material is least stable among the three kinds of composite materials, and the particles will aggregate in long time melt state or low shear field.The facts indicate that aggregation mechanism of dispersing phases in polymer/polymer nanocomposite is different from normal polymer blends. Further investigation will be needed.The investigation on dynamic rheologic behavior of polymer/ polym -er nanocomposite indicates that composites show solid-like behavior in low frequency range as long as the content of PMMA(HC) particles is above a constant value, similar to inorganic nanoparticles/polymercomposites. But the exuding value is between 10% and 15%, larger than inorganic/polymer composites. This result indicats that the processibihty of polymer/polymer nanocomposites is better than inorganic/polymernanocomposites.