Syntheses and properties of stable polymeric bilayer vesicles

Abstract

Amphiphilic methacrylate monomers having cholesteryl or dialkyl groups as hydrophobic moiety were synthesized and the vesicle formation were carried out by sonication and by polymerization. Morphological and physical properties of these vesicles were investigated by electron microscopy, spectroscopic methods, differential scanning calorimetry, liquid scintillation counting, and transport of substrates through polymetric bilayer membranes. Cholesteryl amphiphilic methacrylate monomer, cholesteryl-oxycarbonyl-methyl 2-(methacryloyloxy)ethyl dimethyl ammonium chloride, coded as CHODMA was synthesized from cholesteryl chloroacetate by reacting with 2-(dimethylamino)ethyl methacrylate. CHODAMA was soluble in water giving a viscous solution. Upon polymerization of CHODAMA (0.5\% in water) by free radical initiator or by UV irradiation the viscosity of the solution dropped as the Polymerization proceeded, indicating that the vesicles were being formed during the polymerization process. Electron micrographs and entrapment of [$^{14}C$]sucrose confirmed that the polymer of CHODAMA thus prepared formed well defined closed microvesicles (diameters ranging between 200 and 500 $\mbox{\AA}$). Poly(CHODAMA) vesicles were stable for at least several months and were highly stable thermally, exhibiting no notable change upon heating up to 80$^\circ$C. A double alkyl chain amphiphilic methacrylate monomer, $\alpha$, $\alpha$``-(dihexadecyloxy)glyceryl-oxycarbonyl-methyl 2-(methacryloyloxy)ethyl dimethyl ammonium chloride, coded as HELDAMA was synthesized from $\alpha$, $\alpha$``-(dihexadecyloxy)glycerol according to the similar procedure to that employed for CHODAMA. Didodecyl amphiphilic methacrylate monomer, coded as DOLDAMA was synthesized in the similar way from $\alpha$, $\alpha$`` (didodecyloxy)glycerol. DOLDAMA was readily dispersed in water at room temperature, whereas HELDAMA which was more hydrophobic than DOLDAMA could be dispersed in water only at temperatures above ...