Conjugated Polymer Chains in Solution: A New Phase Transition of Poly-4BCMU

Poly-4BCMU solutions in toluene have been studied as a function of temperature by differential scanning calorimetry and resonance Raman scattering. On cooling, two transitions occur around 65 and 55 °C, independent of polymer concentration. The corresponding enthalpy changes are ≈ 2.3 and ⩾ 0.6 kcal per mole of monomer repeat unit, respectively. The colour change is associated to the upper transition, but RRS shows that the polymer electronic structure changes at both transitions. A large hysteresis is observed and on heating the two transitions occur almost simultaneously around 75 °C. Thermal degradation influences the transition temperatures and enthalpies, and the properties of the intermediate phase.