Specific dissociation behavior of a polycarboxylate having three kinds of hydroxyl groups
Dissociation behavior of a hydrophilic copolymer having three kinds of hydroxyl groups, ie primary OH on α‐hydroxyallyl alcohol component, hemiacetal OH on cyclic hemiacetal component and tertiary OH on α‐hydroxyacrylate component, was investigated as a function of the polymer constitution to study effects from possible intramolecular hydrogen bonds between the carboxyl group and those hydroxyl groups. The apparent dissociation constant, pKa, decreased with increasing fraction of the hemiacetal component, suggesting that the carboxyl anion is stabilized by intramolecular hydrogen bonding with the hemiacetal OH group. Furthermore, the decrease in pKa value was more significant at the lower degrees of dissociation, α. This dissociation behavior was found to be consistent with IR peak shifts to higher wavenumbers observed for the asymmetric vibration band of —COO−, which were more significant with decreasing α and for copolymers with larger hemiacetal contents. Effects from the lactone ring, formed during titration, on the pKa values are also discussed. Copyright © 2005 Society of Chemical Industry
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Document Type: Research Article
Affiliations: Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-0033, Japan
Publication date: 2005-06-01
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