The results of an extensive study of some dilute solution properties of a series of linear, homogeneous (anionically prepared) polystyrenes (4.8<10−4M<440) over a wide temperature interval (10°<T<110°C) in decalin and toluene are described. The data are used to obtain detailed comparisons among the second virial coefficient A2, the mean-square molecular radius 〈s2〉, the molecular weight M, and the temperature. The empirical correlations thus obtained are compared to theoretical predictions. In particular, it is found that A2M½(〈s2〉/M)0−32 and α2=〈s2〉/〈s2〉0 are each single-valued functions of the interaction parameter z=B(〈s2〉0/M)0−32M½, when B is assumed to have the temperature dependence B=B0[1—(Θ/T)]. Certain theoretical predictions for the dependence of A2M½/α3 on z/α3 are found to adequately describe the form of the observed behavior and can be used as the basis for a satisfactory empirical relation. The observed dependence of α2 on z is satisfactorily predicted by recent calculations of Flory and Fisk. It is expected that the correlations given among A2, α2, and z will be valid for any flexible, nonionic polymer.

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Static and dynamic polarized and depolarized light scattering characterization of dilute solutions of regioregular poly(3-dodecylthiophene) is described to study intermolecular association as a function of the thermal history of the solutions. It is shown that metastable aggregation obtains under all of the conditions studied, including temperatures as high as 65 °C. Under some conditions, the aggregated moiety appears to have a disklike shape at room temperature, with appreciable depolarized scattering, attributed to an extended chain structure, consistent with the formation of the lamellar suprastructure characteristic of the bulk, with the polythiophene chains adopting an extended conformation and forming a nematic phase in a polythiophene lamella faced by lamellae rich in alkyl chains. Under other conditions, especially at low temperature, elongated supramolecular structures are formed, with the polythiophene chains in an extended conformation. The reversible thermochromic effect is associated with enhanced order of the alkyl side chains with decreasing temperature, facilitating coplanar conformers in the polythiophene backbones, with the attendant enhancement in the π−π* transitions of the thiophene ring electronic absorption spectra. This behavior is analogous to the events in the thermochromic event in the bulk. Such supramolecular structures could intervene in normal film casting solution processing, with effects on the electronic or optical properties of the cast film. This interpretation of the light scattering data suggests strategies to enhance or suppress lamella formation in solvent-cast films.

The angular distribution function P(θ) for intensity of light scattered by a dilute solution of comblike branched molecules has been determined for three situations of some interest for evaluation of experimental data: (1) the molecules are identical with branches of equal length attached equidistantly along linear backbone chains; (2) the molecules are homogeneous in mass, with the same number of branches on each molecule, but the branches are distributed at random along the chain; (3) branches and main chains are still uniform, but the molecules are heterogeneous in mass with the number of branches per molecule distributed according to the binomial distribution and the branches in any molecule spaced randomly along the backbone. Examination of numerical results shows that the scattering functions for models (1) and (2) are not very different. The function for case (3) is somewhat different from the others when the mean number of branches per molecule is small but they contain a large fraction of the mass of the molecule. Over a limited range of the pertinent variables (corresponding roughly to observations on typical vinyl polymers of molecular weights up to 106) all three functions agree quite well with P(θ) for homogeneous linear chains with the same mean‐square radius of gyration.