Transition Phenomena in Poly(diacetylene) Solutions Studied by Electric Birefringence Measurements

An external electric field induces strong birefringence in solutions of poly(diacetylenes) when they are in the red (low temperature) form. The transient behaviour and the field‐strength dependence of the steady‐state birefringence reveal that the orientation of particles is predominantly due to a permanent dipole moment rather than to the anisotropy of polarizability. The estimated permanent dipole moments are in the order of tenthousand Debye units, this order of magnitude being incompatible with single macromolecules. Thus the view that aggregated particles are formed at low temperatures is supported by our experiments.