2007 Volume 35 Issue 1 Pages 1-9
Zirconium oxide (ZrO2) particles are dispersed in polystyrene (PS)/poly(butyl methacrylate) (PBMA) and PS/poly(methyl methacrylate) (PMMA) blend melts with bicontinuous structure. ZrO2 particles enter exclusively into PBMA phase in PS/PBMA blend, while the particles exist in both phases in PS/PMMA blend. The main cause for the exclusive localization in PBMA phase is the lowest entropy loss of the most flexible PBMA chains among the three polymers due to adsorption onto ZrO2 particles. In PBMA phase, spherical aggregates of ZrO2 particles are formed at a concentration of 11 vol%, while ZrO2 particles make linear arrays at 21 vol% and branches at 29 vol%. These arrays and branches give very high second-plateau in G' at low frequencies. In PS/PMMA blend melt, linear arrays and branches appear in both phases even at 4.4 vol%, and network structure is formed at 11 vol%. Due to the structural difference, the PS/PMMA/ZrO2 composite gives much higher second-plateau than that of PS/PBMA/ZrO2, when compared at the same vol% of ZrO2. A peculiar network structure is observed in PS/ZrO2 composite at a low concentration of 4.4 vol%. The low value of G' close to that of the matrix at intermediate frequencies with a small number of spherical aggregates indicates very weak adsorption of PS chains to ZrO2 particles.