Quantitative description of the metathesis polymerization/depolymerization equilibrium in the 1,4‐polybutadiene system, 3. Influence of the solvent

Continuing our investigation into the field of the metathesis polymerization/depolymerization equilibrium in the 1,4-polybutadiene (resp. cyclobutene) system, the solvent influence was studied (hexane, methylcyclohexane, toluene, trichloromethane, dichloromethane, chlorobenzene). A significant solvent influence on the configuration equilibrium of ttt/ctt-CDT was found. This could be explained by the different dipole moments of ttt- and ctt-CDT. The saturation concentration of the trimeric rings is also solvent dependent. Because the trimeric rings are the dominant cyclic compounds (in particular the ttt-CDT), the integral turning point (integral ring saturation concentration) is solvent dependent as well. Furthermore, the solvent influences the configuration equilibrium of the chains. A distinct influence is found in the region of the precipitation point, which itself is strongly solvent dependent. The precipitation point could be correlated successfully with the Hildebrandt parameter system, leading to optimal solvents with Hildebrandt parameter of about 19 (J/cm 3 ) 0.5 for highly trans-1,4-polybutadiene. This result is in good agreement with the value calculated for the polymer, using the Hoy increment method yielding 18.9 (J/cm 3 ) 0.5 . In this context it is remarkable that by determining the solvent and temperature dependent saturation concentration of the main ring (all-trans-CDT), which can be done very exactly, it is possible to quantify the polymer/solvent interaction.