Behavior of polymer chains grafted from latex particles at soft interfaces

We have studied the behaviors of a poly(methyl methacrylate) (PMMA) chains anchored to polystyrene particles at air/water and oil/water interfaces to recognize the roles of oil molecules in the PMMA property at the interfaces. Through the comparison of pi-A isotherms we found two aspects of unique structural and rheological characteristics observed in PMMA-grafted polystyrene latex (PSL-PMMA) monolayer system in common. (1) The pi-A isotherms showed surface pressure increase at larger occupied area compared to the PSL-PMMA size in solution at three different types of interfaces in most cases. (2) Compressional modulus, C (s) (-1), obtained by pi-A isotherm analysis for PSL-PMMA at interfaces, showed the tendency to decrease with molecular weight of PMMA. This is opposite to that of PMMA homopolymer at interfaces. The effect of oil molecules on PSL-PMMA system at interfaces are found both in the difference of occupied area and C (s) (-1). The occupied areas were larger for the isotherms at the oil/water interfaces than those at the air/water interface in most cases, which suggested the reduced attractive interactions between anchored polymers by oil molecules. On the other hand, C (s) (-1) of PMMA monolayers is strongly dependent on the constituents of the interface and the order of C (s) (-1) is air/water > decane/water > dibutyl ether/water interfaces. The difference between oil species was not explained only by PMMA/oil interaction in bulk, but we suggested that interfacial tension of oil/water interface affects the miscibility of oil molecules with PMMA to cause higher miscibility between PMMA and dibutyl ether at the oil/water interfaces.