Soluble aramid containing ether linkages: Synthesis, static and dynamic light scattering studies

Aromatic polyamide was synthesized via condensation polymerization of 4,4′-oxydianiline and isophthaloyl chloride using N,N′-dimethyl acetamide as solvent under anhydrous conditions. Aramid has been studied by laser light scattering (LLS) in dimethyl sulfoxide, a thermodynamically good solvent at 20 °C. Static and dynamic light scattering studies permitted to determine the weight average molecular weight 〈Mw〉, radius of gyration 〈Rg〉, second virial coefficient A2, the hydrodynamic radius RH and the diffusion coefficient D. Light scattering experiments were conducted at five concentrations ranging from 0.2 to 2 g/L. This LLS method should also be very useful in the study of aggregation or association in a polymer system as long as the large “clusters” are reasonably stable in time. The intensity autocorrelation function obtained on the quasi-elastically scattered light showed a simple diffusive relaxation mode. The ratio of radius of gyration to the hydrodynamic radius, i.e., 〈Rg〉/〈RH〉 ∼ 1.5, indicates that the polyamide chain has coil conformation in DMSO at 20 °C.