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 polymerizatio n/depolymerization equilibrium in the 1,4-polybutadiene (resp. cyclobutene) system, the solvent influence was studied (hexane, methylcyclohexane, tolu ene, trichloromethane, dichloromethane, chlorobenzene). A significant solve nt influence on the configuration equilibrium of ttt/ctt-CDT was found. Thi s could be explained by the different dipole moments of ttt- and ctt-CDT. T he saturation concentration of the trimeric rings is also solvent dependent . Because the trimeric rings are the dominant cyclic compounds (in particul ar the ttt-CDT), the integral turning point (integral ring saturation conce ntration) 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 t he Hildebrandt parameter system, leading to optimal solvents with Hildebran dt 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 cont ext it is remarkable that by determining the solvent and temperature depend ent saturation concentration of the main ring (all-trans-CDT). which can be done very exactly, it is possible to quantify the polymer/solvent interact ion.