A Semi-Theoretical Equation for the Chain Dimension in Dilute Solutions and Its Experimental Verification, and the Coil-Globule Transition

Abstract

A semi-theoretical equation for the chain dimension in dilute solutions based on the perturbational mean field theory, as-a3 = VoM(I-{jjT)Mll2 + v3(a-3-I) was proposed (a, the expansion factor; if, the temperature at which the second virial coefficient of polymers A2 = 0; v0M and v3, phenomenological constant; M, the molecular weight; T, the absolute temperature). In derivation of the equation, the difference between e (the temperature at which the second virial coefficient of segments v2 =0) and if was taken into the consideration. Experimental verification was done by the polystyrene-cyclohexane, methylcyclohexane, and benzene solutions. The equation represented the experimental results well in the wide range of (I-ifiT)M 112 • The sharpness of the coil-globule transition was discussed. It was concluded that the coil-globule transition is not a phase transition type but a cross-over type at least in the polystyrene-cyclohexane solution. KEY WORDS Chain Dimension I Theta Temperature I Excluded Volume Effect I Expansion Factor I Polystyrene I Coil-Globule Transition I