Thermodynamic behavior of poly(cyclohexylethylene) in polyolefin diblock copolymers

We report the temperature dependence of the Flory-Huggins interaction parameter for three symmetric diblock copolymer systems containing poly(cyclohexylethylene) (PCHE): poly(cyclohexylethylene-b-ethylene) (CE), poly(cyclohexylethylene-b-ethylethylene) (CE_E), and poly(cyclohexylethylene-b-ethylenepropylene) (CP). Order-disorder transition temperatures (T_ODT) were determined using dynamic mechanical spectroscopy and interpreted with mean-field theory, (χN)_ODT = 10.5, leading to well-defined expressions for χ(T). These results have been analyzed in the context of solubility parameter (δ) theory resulting in a unique parameter δ_C that describes the interactions in CE, CP, and CE_E, where δ_C < δ_EE < δ_P < δ_E with (δ_E - δ_C) ≈ 1.6 MPa^1/2 at 500 K. In contrast to the predictions of group contribution theory, this indicates that δ_C is in surprisingly close proximity to the solubility parameter for poly(dimethylsiloxane).