In the preparation of novolac resins, three possible dimers with slightly different molecular dimensions may be produced in the polymerisation reaction. Gel permeation studies were carried out on four novolac resins prepared using different acid catalysts, and the results indicated that the nature of the catalyst influences the type and quantity of dimer produced. The weight and number average molecular weights were also calculated from the chromatograms obtained.
The design and construction of a large‐scale gel permeation chromatographic unit is described, and it is a tenfold scale‐up of the usual analytical instrument. Important aspects of the column packing procedure are given. Fractions prepared using this apparatus were isolated and reinjected into an analytical instrument. In this way the efficiency of preparative fractionation was investigated using several polystyrene samples covering a wide range of molecular weights and distributions. Generally the highest molecular weight fraction isolated from a sample had the narrowest molecular weight distribution.
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