| Nanoparticles have been extensively used to tailor the performance of polymeric materials, yielding the nanoparticle filled polymeric materials with significant physical reinforcement and/or multi-functional capabilities for satisfying the continuous requirements from advanced industrial sectors. The nanoparticles are c easy to aggregate due to their large surface energy. Hence, the dispersion and distribution of nanoparticles in polymer matrix, especially in polymer blend matrix, may have a significant effect on the mechanical and other properties of the namocomposite. The in situ grafting modification of nanoparticles will be beneficial to their uniform dispersion in the matrix and their selective distribution in the polymer blends would further contribute to control the performance of polymer composites. The sufficient understanding to the influence of the dispersion and distribution of nanoparticles in the blend matrix on the phase behavior of blend matrix may provide a theoretical basis for designing and preparing high performance nanocomposites.In this dissertation, poly (methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) blends were selected as a polymer matrix, soap-free emulsion polymerization was adapted to graft PMMA chains on the surface of clay. The selected distribution of clay owning different grafting density in PMMA/SAN system and its effect on the phase behavior of PMMA/SAN were investigated. The reasons of selected distribution of clay with different grafting density were studied by transmission electron microscopy (TEM), dynamic rheometer, differential scanning calorimetry (MDSC) and contact angle meter. The effect of selected distribution of modified clay on phase behavior was studied by small angle laser light scattering (SALLS) and dynamic rheometer.By changing the amount of iniator via soap-free emulsion polymerization, Clay-K0.2, owing a relatively low grafting density, and Clay-K1.2, owing a relatively high grafting density, were got. Both kind of modified Clay homogeneously dispersed in polymer blends matrix at exfoliated and intercalated structure. When the phase separated of PMMA/SAN system, two kind of Clay didn’t migrate to the PMMA-rich phase, but took place a special selective distribution. Clay-K0.2 would locate in SAN-rich phase for a long time and eventually migrate to the interface. Clay-K1.2 would locate in the interface of PMMA/SAN stably when phase separated. The dispersion and compatibility of modified Clay in SAN matrix were much better than that in PMMA matrix when dispersed the Clay in PMMA or SAN respectively. The MDSC results show that there are immobilized SAN chains on the Clay-K0.2 and Clay-K1.2 in the SAN/Clay system, but there are doesn’t exist immobilized PMMA chains in the PMMA/Clay system. Thus, when PMMA/SAN phase separated, modified Clay were prone to locate in SAN-rich phase, and finally, Clay would migrate to the interface under the interfacial tension after annealled for a long time. Compared with Clay-K0.2, Clay-K1.2 had a relatively high grafting density, and most of them were existed at exfoliated state. Thus, when the polymer blends phase separated, Clay-K1.2 would migrate from SAN-rich phase to interface rapidly.Owning to the different distribution of Clay-K0.2 and Clay-K1.2, the influence of two fillers on phase behavior of PMMA/SAN were also different. The results from SALLS and dynamic rheometer showed that the hindering phase separation effect of Clay-K1.2 was remarkable than Clay-K0.2. When the phase separated of PMMA/SAN system, Clay-K1.2 would locate in the interface of PMMA/SAN stably, thus the pathway of polymer chains migrating had decreased. So that, the retard effect of Clay-K1.2 on phase separation of PMMA/SAN system was more obvious than Clay-K0.2. And for Clay-K0.2 would locate in SAN-rich domains when phase separated, the viscosity of SAN/Clay-K0.2 phase had increased, and thus the phase separation process was slowed down.For PMMA/SAN/Clay ternary nanocomposites system, the TTS principle and WLF equation were also appliable to describe the SD phase separation behavior. That was to say although the retard effect of Clay-K0.2 and Clay-K0.2 on phase separation of PMMA/SAN system had difference, however, filler had no effect on the molecular chains viscous diffusion essential in the phase separation process. |
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