Determination of end groups as a function of molecular size for aliphatic polyesters by derivatization of end groups and size-exclusion chromatography with infrared detection |
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Authors: | Sadao Mori |
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Institution: | Department of Industrial Chemistry, Faculty of Engineering, Mie University, Tsu Mie 514 Japan |
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Abstract: | End groups of poly(ethyleneglycol sebacate) having number average molecular weights less than 2500 were characterized as a function of molecular size by derivatizing end groups separately to form 3,5-dinitrobenzoyl and p-nitrobenzyl esters. A hydroxyl end group was reacted with 3,5-dinitrobenzoyl chloride (DNBC) and a carboxyl end group was reacted with O-(p-nitrobenzyl)-N,N′-diisopropyl isourea (PNBD). After separation of these derivatized polyesters by size-exclusion chromatography, the effluent was monitored by using a highly sensitive infrared detector. Concentrations of polyesters were monitored at 1740 cm?1 for a carbonyl group in the main chain, polyesters derivatized with DNBC at 1560 cm?1 for a hydroxyl end group (characteristic absorption band for the nitro group of DNBC), and polyesters derivatized with PNDB at 1537 cm? for a carboxyl end group (a characteristic absorption band for the nitro group of PNBD). By this technique, three types of polyesters having different end groups were characterized: a diol-type polyester, a mixture of polyesters of a diol type and a mono-ol/monocarboxyl type, and a mixture of polyesters of a dicarboxyl type a mono-ol/monocarboxyl type. |
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