Synthesis and Catalytic Properties of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium bromides) Having Decyl, Octyl, and Hexyl Side Chains

Abstract

A family of non-cross-linked and cross-linked copolymers containing decyl, octyl, and hexyl groups as side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) were synthesized by radical-initiated cyclocopolymerization of alkylmethyldiallylammonium bromide monomers without and with a small amount of N,N'-methylenebisacrylamide as a cross-linking agent in aqueous solution. Their H-1 NMR and IR spectra indicated the presence of five-membered rings cross-linked without and with N,N'-methylenebisacrylamide in the macromolecules. Viscosity measurements showed that the cross-linked copolymers exhibit a larger reduced viscosity in aqueous solution with increasing cross-linking agent content in the copolymers. For(CL)-CopolC1-10, the conformational transition to compact coils was indicated by changes of the reduced viscosity in dilute aqueous solutions. At higher concentrations, intermolecular aggregation was also revealed and increased with increasing the percentage of cross-linking for CL-CopolC1-10. (CL)-CopolC1-8 and (CL)-CopolC1-6 showed extented molecular dimensions in aqueous solution. The hydrophobic microdomains of the non-cross-linked and cross-linked copolymers were probed by hypsochromic shifts of the long-wavelength absorption band of Methyl Orange as a solvatochromic agent, noncovalently bound to the macromolecule. The unimolecular decarboxylation of 6-nitrobenzisox-azole-3-carboxylate (6-NBIC), catalyzed by these copolymers in aqueous solution, was used as a model reaction to study the influence of polysoap microenviroment on reactivity. Depending on the hydrophobic group content, (CL)-CopolC1-10 led to a remarkably large rate enhancement, whereas (CL)-CopolC1-8 induced only modest rate acceleration for the decarboxylation of 6-NBIC. A small rate enhancement was observed in the presence of(CL)-CopolC1-6. The decarboxylation rate is also sensitive to changes of the percentage of cross-linking in the macromolecules. A maximum in rate constant was found at about 0.2% (w/w) cross-linking agent for CL-CopolC1-10 and at about 0.4% (w/w) for CL-CopolC1-8 in plots of the rate constant vs cross-linking agent content.