A rod-to-coil conformational transition is demonstrated for polydiacetylene, 4-butoxycarbonylmethylurethane, in solution. With use of quasielastic light scattering, a coillike structure with relatively small hydrodynamic radius is indicated for the polymer in a good solvent, CH${\mathrm{Cl}}_3$. As the proportion of nonsolvent (hexane) is increased, the hydrodynamic radius increases abruptly to a value consistent with the molecule being a rigid rod.

• Received 25 January 1983

DOI:https://doi.org/10.1103/PhysRevLett.50.1934