The ability of nine amphiphilic quaternary ammonium derivatives of cholesterol to form small unilamellar vesicles in water has been investigated using the entrapment of [14C]sucrose coupled with gel filtration. In all cases vesicles were detected and the proportion of [14C]sucrose entrapped suggested that these were indeed of the small unilamellar type. In the case of one amphiphile with a pyridinium ion head-group, studies over a period of four weeks showed the vesicles to be very stable, although there was some evidence for fusion and growth of the lamellar structures. Five of the amphiphiles also contained a polymerizable methacrylate group. Photoinitiation of polymerization of these in aqueous dispersions using 2,2-dimethoxy-2-phenylacetophenone as the initiator yielded only oligomeric products with DP,~5-13. In contrast polymerization in isotropic benzene solutions using thermal fragmentation of azobisisobutyronitrile yielded polymers with DP, up to ~ 180. In aqueous solution the 'rigid' bilayer structures may impose some additional steric restriction to polymer growth, a restriction that is absent in benzene solutions.
Посилання на статтю:
Quaternary ammonium derivatives of cholesterol: polymerization and vesicle formation / S. K. Abid* and D. C. Sherrington // Polymer. – 1992. – Vol 33. – P. 175-180.