The Influence of polymer-grafted lipids on the physical properties of lipid bilayers: A theoretical study

Experimental studies of bilayers containing polymer-grafted lipids have been underway for some time now. Modeling the physical properties of these bilayers, however, is not trivial because of the complexities in the self-assembling polymer-lipid/lipid bilayer system and the mutual influence of its two components: the lipid bilayer and the grafted polymer. In the paper we study the influence of the grafted polymer on the structural and interactive properties of the lipid bilayer. The modeling is done in terms of some existing polymer theories (de Gennes’ scaling theory, Flory’s and Milner’s mean-field theories). We propose a simple lateral pressure model to calculate the critical concentration of polymer-lipid that can be incorporated into the bilayer. We study the influence of the polymer chains on the tensile strength of the bilayer and model the dependence of the elastic coefficients K_A, k_c, and k^¯_c on the concentration and molecular weight of the grafted polymer. For two bilayers in close proximity the interbilayer steric interactive forces are modeled for different polymer-lipid concentrations.