Viscosity studies of some polyamides dissolved in mixed solvents (cosolvents)

The solubility of poly (octamethylene sebacamide) (POS), poly (octamethylene terephthalamide) (POT) and poly (octamethylene tetrachloroterephthalamide) (POTC1), in m-cresol cyclohexane mixtures, a cosolvent system, has been studied by measuring the intrinsic viscosity [η], at 25°C. The intrinsic viscosities of POT, POS and POTC1 in various solvent/non-solvent mixtures are higher than the corresponding intrinsic viscosities in the pure solvent m-cresol. The POT and POTC1 polyamides exhibit a sharp increase in [η] values compared with the corresponding small increase in the POS polyamide. The POTC1 polyamide presents a true cosolvency effect in m-cresol cyclohexane mixtures; m-cresol and cyclohexane are non-solvents for this polyamide. The cosolvent behaviour is discussed in terms of the most energetically favourable interactions. The aromatic ring in POT and POTC1 would expand the chain, would favour a better packing between neighbouring solvent molecules and would favour the selective adsorption in the cosolvent system.