Self-association of cholesterol-end-capped poly(sodium 2-(acrylamido)-2-methylpropanesulfonate) in aqueous solution

Poly(2-(acrylamido)-2-methylpropanesulfonic acid) sodium salt end-capped with a cholesterol moiety (Chol-PAMPS) was prepared by free radical polymerization of 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS) initiated by a cholesterol-substituted azo compound, 4,4‘-azobis(4-cyano-1-cholesteryl)pentanoate, and the associative behavior of Chol-PAMPS in aqueous solution was studied by 1H NMR, size exclusion chromatography (SEC), static light scattering (SLS), quasielastic light scattering (QELS), and fluorescence probe techniques. For a reference polymer (AIBN−PAMPS), polyAMPS of a similar molecular weight with that of Chol-PAMPS was prepared in the presence of 2,2‘-azobis(2-methylpropionitrile) as an initiator. The degree of polymerization (DP) of Chol-PAMPS was estimated to be about 70 from a 1H NMR spectrum (in DMSO-d6) by assuming disproportionation for the termination. This DP value agreed fairly well with that estimated by SEC in water/acetonitrile using sodium poly(styrenesulfonate)s as standards. Q...