Conformational behaviour of poly(2,6-dimethyl-1,4-phenylene oxide) in solution - II. Sedimentation coefficients and permeabilities in the semi-dilute region as a function of temperature

Sedimentation and flotation coefficients of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) solutions have been measured as a function of temperature between 60 and 25°. The solvents were toluene and trichloroethane (TCE). Solvent permeabilities have been calculated from the sedimentation or flotation coefficients. PPO is less permeable to the solvents used than polystyrene of comparable molecular weight is to toluene and cyclohexane. Strong solvation of toluene and TCE by PPO molecules is proposed as an explanation for this finding. The measured permeabilities were used to check an earlier calculation of the change of radius of gyration with temperature from intrinsic viscosity data. A larger decrease in radius of gyration with increasing temperature has been calculated in this way than with the earlier assumption of essentially impermeable polymer coils, i.e. with the assumption of the value 2.5 × 1023 for the universal viscosity parameter