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, (χ N ) 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 E E < 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).