HEATS OF DILUTION OF POLYISOBUTYLENE SOLUTIONS

The measurements of heats of dilution of polyisobutylene solutions in benzene, toluene, and chlorobenzene have been carried out with a Tian–Calvet microcalorimeter at 25 °C. The dilution technique previously described has been improved and the extrapolated enthalpy parameter κ1* for each system has been corrected for the excluded volume effect using the Krigbaum–Carpenter–Kaneko–Roig formulation for the second virial coefficient A2. No detectable variation in κ1* was found for high molecular weights (≥ 43,000); but a definite increase in κ1* was found for very low molecular weights.