Interfacial tension of demixed polymer solutions over a wide range of reduced temperature

Interfacial tensions were measured for solutions of polystyrene-methylcyclohexane, polystyrene-heptamethylnonane and poly(dimethyl siloxane)-phenylethyl ether to investigate the behaviour of the interfacial tension from the critical point to a region far away from it. In the polystyrene-heptamethylnonane system, measurements were performed until the concentration of the polymer rich phase became about 70∼80%. The molecular weight dependence of the interfacial tension was stronger away from the critical temperature than near to it. Data for polystyrene solutions with different solvents were connected by a scaling law. Recent scaling theories were compared with the results for poly(dimethyl siloxane) solution.