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.

Static and dynamic light scattering measurements are reported on dilute solutions of poly(p-biphenylylmethyl l-glutamate), PBPMG, in the helicogenic solvent THF, over a temperature range encompassing an observed reversible transition in the chiral optical properties of these solutions. The results confirm the expected helical conformation for this polypeptide, as well as complete dissolution of the polymer at temperatures above the transition temperature. Association is observed at lower temperatures, with the chains in an ordered parallel array within the aggregates. The association occurs with increasingly poor solvent conditions as the temperature is decreased, with the degree of association in the aggregate increasing concurrently with the change in the optical rotation and circular dichroism (CD) spectrum. It is concluded that the intermolecular association of the chains in the parallel array alters the chiral electronic environment of the biphenyl group, without a conformation change in that chromophore, resulting in the observed transition in the optical rotation and the CD spectrum. Unlike the behavior reported for certain other aggregated systems, the optical transition observed with solutions of PBPMG does not involve the initial formation of a disordered aggregate, which orders itself on reduced solvent quality or temperature, but rather a spontaneous association, such as expected on crossing a phase boundary, with a concurrent optical transition.

Static and dynamic light scattering data are reported on dilute and moderately concentrated solutions of a high molecular weight polystyrene (Mw = 3.61 × 106) in bis(2‐ethylhexyl) phthalate under Flory Theta conditions. The data cover a concentration range with 0.03 × [η]c × 3.5, with several concentrations large enough that the product cMw exceeds the value necessary for entanglement behavior. The results show that a certain intermolecular scattering function H(q, c) often approximated by unity should not be neglected in the evaluation of the correlation length in the static scattering from moderately concentrated solutions of flexible chain polymers. An approximate form for H(q, c) for moderately concentrated solutions is consistent with a soft spherically symmetric repulsive potential among the chains. The dynamic scattering show two distinct groups of relaxation rates at all concentrations, but the interpretation of the two modes changes as the concentration increases from low concentrations ([η]c < 1) to higher concentrations. At low concentrations the slower mode corresponds to mutual diffusion, and the faster mode to intramolecular dynamics. For concentrations with [η]c > 2.4 the slow mode is viscoelastic in origin, and the faster mode is diffusive. The behavior is compared with theoretical predictions in both regimes.