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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface of poly(butylene terephthalate) (PBT) was analysed by means of inverse gas chromatography (IGC). The specific component of the adsorption of polar probes on the surface of poly(butylene terephthalate) was found to be endothermic, and the change in the entropy of the system, positive, which is not a common case in IGC. An interpretation is given, based on the contribution of cleavage of hydrogen bonds in the PBT and formation of hydrogen bonds between the probe-molecules and the polymer. The surface Lewis acidity and basicity constants, Ka and Kb, respectively, were determined and found to correlate well with an analysis of the repeating unit and end-groups in this polymer.
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PMID:Characterisation of the surface Lewis acid-base properties of poly(butylene terephthalate) by inverse gas chromatography. 1238 84

Two grades of poly(butylene terephthalate) were analysed by means of inverse gas chromatography (IGC) and the results correlated with the respective crystallisation properties. The following parameters were determined by IGC: the dispersive component of the surface tension, the enthalpy and the entropy of adsorption of selected polar and apolar probes, and the Lewis acidity and basicity constants, Ka and Kb respectively. The interpretation of the values determined for Ka and Kb is in agreement with the FTIR spectra relating to the carboxyl end-group and the hydroxyl end-group concentrations in these polymers. The differences in the molecular weight values and in the end-group type and concentration, between the two grades of PBT, do not cause differences in the crystallisation activation energy. This observation suggests that there is a leading contribution of the Lewis basic sites to the crystallisation activation energy of the grades of PBT that were analysed. However, the lower value of Ka and the greater molar mass of one of the PBT grades lead to a corresponding lower crystallisation degree.
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PMID:Lewis acid/base character and crystallisation properties of poly(butylene terephthalate). 2557 40