Self-association between nano-sized bilayer and amphiphilic polymer

Abstract

The membrane bending elastic modulus and microstructure were estimated for the vesicles with and without the addition of polymer-surfactant macromolecules by cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS). The mixture of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzensulfonate (SDBS) self-assembles into vesicle phase. In order to examine the effect of polymer addition, Poly (ethylene glycol)-dimyristoylphosphatidylethanolamine is used as the component of added macromolecule. The bilayer bending rigidity is evaluated as 0.5 k(B)T from the size distribution obtained by the image analysis of cryo-TEM regardless of polymer addition. However, it is observed from SANS curves that the width of size distribution is reduced as the amount of polymer is increased because of enhanced bilayer asymmetry after polymer's penetration into membrane. Therefore the mechanism of incorporating polymer into bilayer is understood as that the hydrophobic part of polymer is anchored into the membrane of vesicle following the adsorption onto the surface of vesicle from the aqueous phase.