Properties of an optically anisotropic heterocyclic ladder polymer (BBL) in dilute solution

Light scattering, intrinsic viscosity, gel‐permeation chromatography, and fluorescence depolarization measurements are reported on dilute solutions of a heterocyclic polymer ( BBL ) prepared by polymerization of 1, 4, 5, 8‐naphthalene tetracarboxylic acid with 1, 2, 4, 5‐tetraaminobenzene. The light‐scattering data on fractions of the polymer giving the anisotropy δ and the mean‐square radius of gyration s 2 are discussed in terms of equations for the scattering from polydisperse anisotropic polymer. It is concluded from the dependence of δ and 〈 s 2 〉 on the molecular weight that the polymer has a nearly rodlike conformation. The intrinsic viscosity data are analyzed in terms of relations for rods and wormlike chains. The fluorescence emission anisotropy is found to be so sensitive to molecular‐weight distribution that analysis in terms of molecular parameters is prohibited. Association that can occur under certain circumstances is discussed.