Melting temperatures of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in methylene chloride solutions: Thermodynamic analysis

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Abstract
Melting temperatures were observed visually for poly‐(2,6‐dimethyl‐1,4‐phenylene oxide) in methylene chloride at nine concentrations (polymer weight fractions ranging from 0.0042 to 0.2362). The data were analyzed upon the assumptions that ΔHu and ΔSu, the molar heat and entropy of fusion per polymer unit, are constant over the temperature range studied, and that a Flory‐Huggins chemical potential expression with a concentration‐independent pair interaction parameter, χ1 = (0.5 + ψ1) + ψ1Φ/T, satisfactorily describes the polymer unit activity in the binary solutions. Computation gave ΔHu = 1404 cal/mole of units (therefore Δh = 11.7 cal/g), ψ1 = −0.5691, and Φ = 342.4°K. The effect of using various combinations of data points upon the values of these three parameters, as determined by least‐squares linear regression treatment of the melting temperature expression, is indicated.