An acrylonitrile‐styrene copolymer having 51.4 wt % acrylonitrile content was fractionated using dimethylformamide and a toluene–n‐propanol mixture as solvent and nonsolvent, respectively. From characterization of the fractions, it is shown that the copolymer was fractionated principally in accordance with composition. The weight distribution curve of the copolymer was expressed as a function of both molecular weight and chemical composition on a two‐dimensional contour map. The same plotting technique was applied to a copolymer having nearly the azeotropic composition.
Nylon 12 has a low melting point compared with other commercial products like nylons 6 and 66. Nylon 12 was fractionated by the column elution method at 170.8‐C. The same sample was also fractionated by preparative gel permeation chromatography and the molecular weight distribution of the fractions obtained by these methods was similarly determined. The weight‐average molecular weight of the fractions was also found by the light scattering method. Both fractionation methods separate the sample according to molecular weight. The former, however, had narrower fractions in molecular weight distribution than the latter and it was easy to obtain a large number of fractions. It was also generally superior in practical use.
Molecular weight distribution of Nylon 12 was determined with hexafluoroisopropanol/toluene mixture as eluent by gel permeation chromatography. Calibration curve for Nylon 12 was easily obtained from that of polystyrene because the method of universal calibration was applicable among these polymers. The molecular weight distributions of Nylon 12 were always broader than expected by the theory of polymerization, i.e., most probable distribution. This result was not caused by broadening effect in gel permeation chromatography, but by polymerization itself.
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