Characterization of Nylons by Gel Permeation Chromatography and Low Angle Laser Light Scattering in 2,2,2-Trifluoroethanol

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Abstract
A GPC method was developed for the analysis of several commercial nylons in trifluoroethanol + 0.05M LiBr using a styrene-divinylbenzene column custom-packed by Jordi Associates. A broad molecular weight standard method was developed by interfacing GPC with LALLS to give the absolute molecular weight for each data point or elution volume along the chromatographic peak from a nylon sample of known molecular weight. The integrity of the interface was verified by static LALLS measurements; no loss or adsorption of solute was found in the chromatographic system. A strong ionic effect was observed for nylon samples and the method to alleviate it was described. The molecular weights and distribution of the following nylons were determined by this method: nylon 6, nylon 4,6, and nylon 6,6. Much higher than quoted molecular weights were obtained for nylons when polymethyl methacrylates and ethylene glycols were used as standards; this necessitated the use of this broad molecular weight method for column calibration. The ambient operating conditions offered several advantages over the conventional m-cresol solvent which required operation at higher than 100 C in order to reduce the viscosity, possessed a strong odor, and occasionally resulted in degradation of polyamides.