Ring-chain interactions in solutions of cyclic and linear poly(methylene) ester oligomers in p-dioxan and chloroform

The thermodynamic behavior of ternary solutions containing one cyclic (CYC10 and CYC20) and one linear (LIN10 and LIN20) poly(methylene) ester oligomer, respectively, in p-dioxan and chloroform were investigated through vapor-pressure measurements. Experiments were carried out at 25, 30, 35, and 40 degreesC. The ring-chain interaction parameters chi" were evaluated using the Leonard's equation for a ternary polymer solution containing one ring polymer. Results indicated that the values of chi" are concentration and solvent dependent, and they vary with molecular size and slightly with temperature. All chi" values were positive for both CYC10/LIN10 and CYC20/LIN20 blends, with the higher values for the former system, indicating that both ring-chain oligomer blends are nearly immiscible, and the difference between cyclic and linear oligomers decreases as molecular size increases. The positive chi" agrees with differential scanning calorimetric measurements performed on ring-chain oligomer blends that show two distinct endotherms for the blends. (C) 2002 Wiley Periodicals, Inc.