Thin-layer chromatography (TLC) combined with concentration gradient development has been applied to the determination of the molecular weight distribution of polystyrene prepared by a radical polymerization. Developers obtained by mixing polar nonsolvents with moderately good solvents toward polystyrene were found to give complete separation of polymer according to molecular weight. It was proved that the molecular weight distribution deduced from the present TLC experiment was in good agreement with that from a gel-permeation chromatography experiment.
Notes 133 polymer crystallization kinetics, giving results similar to conventional methods. No diluent effects1 23were noted, probably because the decane was mixed with the polymer in extremely small amounts and for an insignificant portion of the total crystallization time. Furthermore, crystallinity measurements using different probe molecules and column conditions gave essentially the same crystallinity for a given polymer sample.7 One useful feature of the method is that retention times may be measured easily to high precision. However, very accurate temperature control and carrier gas flow control are necessary to exploit the method's inherent sensitivity to small changes in crystallinity. Another advantage of this method is that very thin layers of polymer may be studied. (For this work the average coating thickness was less than 10-3 cm, assuming that all the glass surface was covered.) The effects of high surface-to-volume ratios and of different types of support surfaces on the rate of polymer crystallization are thus readily measurable.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.