Phase Separation of Poly(methyl methacrylate)/Poly(styrene-co-acrylonitrile) Blends with Controlled Distribution of Silica Nanoparticles

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• 作者：Chongwen Huang ; Jianping Gao ; Wei Yu ; Chixing Zhou
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：October 23, 2012
• 年：2012
• 卷：45
• 期：20
• 页码：8420-8429
• 全文大小：655K
• 年卷期：v.45,no.20(October 23, 2012)
• ISSN：1520-5835

文摘

Effects of selective location of silica nanoparticles on the phase separation of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) (PMMA/SAN) blends were investigated via combination of rheological method and optical microscopy. Through grafting polystyrene chain to the surface of silica nanoparticles, the silica nanoparticles were controlled to selectively locate at interfaces or in the PMMA-rich domains. Power-law analysis of the moduli and shifted Cole鈥揅ole plots were applied to determine rheological transition temperature (apparent binodal temperature) of blend with near-critical and off-critical compositions for both neat blends and particle-filled blends. The particle location had significant influence on the rheological transition temperature but little impact on optically determined binodal temperature. This discrepancy was discussed through morphology observation via transmission electron microscopy (TEM) for blends under different phase separation conditions. It was found that nanoparticles retard coarsening of morphology during phase separation. The most striking slowdown was found in off-critical blends with nanoparticles located on the interface. On the other hand, nanoparticles preferentially locating in the minor phase could act as nucleation sites but decreased the total number of nuclei. The difference in the rheological transition temperatures is ascribed to the effect of nanoparticles on the components鈥?viscoelasticity and the morphology during phase separation.