Location of the Theta Temperature

The theta temperature of a polymCT-solvent systen can be measured from phase separation studies. The value of at the critical concentration is related to the chain length of the polymer by Equation 8.39, and substitution in Equation 8.45 leads to 

Remembering that = (MV2/V1), where M and V2 are the molar mass and partial specific volume of the polymer, respectively, and is the molar volume of the solvent, the equation states that the critical temperature is a function of M and the value of at infinite M is the theta temperature for the system. 

FIGURE 8.4 Chain length dependence of the upper critical consolute solution temperature for (1) polystyrene in cyclohexane and (2) polyisobutylene in di-isobutyl ketone (data from Schultz, A.R. and Flory, P.J., J. Am. Chem. Soc., 74, 4760, 1952), and the lower critical solution temperature for (3) polyoctene-1 in w-pentane (data from Kinsinger, J.B. and Ballard, L.R, Polym. Lett., 2, 879, 1964). 

Theta Temperatures and Entropy Parameters for Some Polymer-Solvent Systems 

Note Values have been derived using Equation 8.47 0=theta temperature, / = entropy of dilution. 

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