Study of the pressure effect on polydiacetylene in good solvent

Abstract We have done visible absorption spectroscopy on p4BCMU in THF up to 20 kilobars. A red shift of the maximum of the absorption spectrum is observed as a function of the pressure. The change is continuous, reversible and does not exhibit any hysteresis. This result is a strong indication that an homogeneous solution remains at all pressures. The red shift can not be related to an aggregation process or a gel formation as it is for p4BCMU in toluene. The red shift can be explained either by a solvent change or a conformational change of the chain. From the comparison with experiments made on short oligomers we discuss the two possibilities.