DEGREE OF POLYMERIZATION OF A VESICLE MEMBRANE (SIZE-EXCLUSION-CHROMATOGRAPHY, GELIPEREATION)

The present work is aimed at determining the membrane composition of polymerized vesicles and determining how exactly the membrane composition and membrane stability are influenced by the specific method of polymerization used. Vesicle dispersions of dimethyl-n-hexadecyl-{11-(methacryloyloxy) undecyl} ammonium bromide in water (both well-sonicated and non-sonicated) were prepared and polymerized by the free radical initiator, 2,2\u27 -azobis (2-methyl propionitrile) and by UV-irradiation. The polymers formed within the vesicles were isolated by freeze drying. The Mark-Houwink-Sakurada constants and absolute molecular weight averages for the polymers were determined by size-exclusion chromatography-viscometry. The non exclusion effects due to adsorption and polyelectrolyte expansion have been shown to be minimal in the size-exclusion chromatographic measurements. The degree of polymerization within AIBN-polymerized vesicles was considerably higher than that within UV-polymerized vesicles. Based on the number average degree of polymerization and using electron micrographic data the number of polymer molecules per vesicle was estimated to be 3 to 60 for AIBN-polymerized vesicles and 15 to 300 for UV-polymerized vesicles. Polymerization of the vesicles were also carried out under different conditions and the effect of polymerization condition on the degree of polymerization within the vesicles has been studied. Explanations for the observed results are given. The stability of the vesicles towards ethanol and Triton X-100 have also been determined and the results indicate that the stability of the vesicles increases as the degree of polymerization increases