Macromolecular flexibility and aggregation tendency of non-cross-linked and cross-linked cationic polysoaps

Abstract

The aggregation tendency of non-cross-linked and cross-linked poly(alkylmethyl-diallylammonium halides) bearing n-dodecyl and n-decyl side chains ((CL)-CopolC1-12-Cl, (CL)-CopolC1-12-Br and (CL)-CopolC1-10-Br, respectively) in aqueous solution has been evaluated by measuring their critical aggregate concentration (CAC). Polysoaps (CL)-CopolC1-12-Cl, (CL)-CopolC1-12-Br and (CL)-CopolC1-10-Br all show the same change of their aggregation tendency accompanying an increase in the content of the cross-linking agent. The aggregation tendency of these polysoaps clearly depends upon their macromolecular flexibility that varies inversely with the cross-linking agent content. The decrease of the macromolecular flexibility that results from an increase in the cross-linking agent content leads to an increase in the aggregation tendency which reaches a maximum at 0.20% cross-linking agent content. The propensity for aggregation then decreases with a further decrease of the macromolecular flexibility. Most strikingly, this conclusion is confirmed by the consistency with catalytic effects of these non-cross-linked and cross-linked polysoaps on the unimolecular decarboxylation of 6-nitrobenzisoxazole-3-carboxylate anion (6-NBIC). It is suggested that increased aggregation tendency accompanying decreased macromolecular flexibility for cross-linked polysoaps with a smaller cross-linking agent content should be attributed to an increase of intramolecular micellization.