Synthesis and catalytic properties of hydrophobically modified poly(alkylmethyl-diallylammonium chlorides)

Abstract

Novel non-cross-linked and cross-linked, hydrophobically modified homo- and copolymers were synthesized by free-radical cyclo(co)polymerization of alkylmethyldiallylammonium chloride monomers in aqueous solution using ammonium persulfate as the initiator. Cross-linking was brought about by addition of a small amount of N,N′-methylenebisacrylamide. The cross-linked homo- and copolymers showed an increase of their reduced viscosity in aqueous solution upon the controlled introduction of cross-linking agent into their chemical structure. Viscosity measurements revealed that the conformational transition of polysoaps to compact coils in aqueous solution is strongly dependent upon the hydrophobic group content of the polysoaps. The formation of hydrophobic microdomains is akin to intramolecular micelle formation. Depending on the hydrophobic group content and the percentage of cross-linking, intermolecular aggregation was also revealed by viscosity measurements at higher concentrations of polysoap. The hydrophobic microdomains of the non-cross-linked and cross-linked polysoaps were characterized by hypsochromic shifts of the long-wavelength absorption band of Methyl Orange as a solvatochromic probe, non-covalently bound to the macromolecule. Catalysis of the unimolecular decarboxylation of 6-nitrobenzisoxazole-3-carboxylate by the non-cross-linked and crosslinked copolymers was investigated in aqueous solution at pH 11.3 and 30 °C. The cross-linked polysoaps exhibited higher catalytic activities for decarboxylation than the corresponding non-cross-linked analogues. A maximum in rate constant was found at about 0.2% (w/w) of cross-linking agent in the cross-linked polysoaps. The decarboxylation rate is strongly dependent upon the hydrophobic group content in the polysoaps.