Thermodynamic Interactions in Model Polyolefin/Polydiene Blends

The Flory-Huggins interaction parameter $\chi$ is used to describe the interactions between polymers and is of crucial importance in determining the processing conditions for polymer mixtures and block copolymers. The temperature dependence of $\chi$ between 1,2-polybutadiene and saturated 1,2-polybutadiene was investigated. 1,2-Polybutadiene was synthesized by anionic polymerization with 1,2-dipiperidinoethane as an additive to achieve high vinyl content (99.0\%). The synthesized 1,2-polybutadiene was saturated with deuterium to provide contrast for small-angle neutron scattering (SANS) experiments. Two series of blends were prepared with differing molecular weight. Values of $\chi$ were extracted from fitting the Random Phase Approximation (RPA) to SANS data. Additionally, $\chi$ was extracted from Zimm analysis, using the low-angle scattering intensity. $\chi$ extracted by RPA and Zimm analyses were in good agreement. The temperature dependencies of $\chi$ characterized for two separate blends of differing molecular weight were consistent with one another. The large $\chi$ parameter observed in this system indicates strong repulsion in blends of polydienes and polyolefins.