Effect of Bilayer Thickness on Membrane Bending Rigidity

TL;DR

This study measures how the bending rigidity of bilayer vesicles made from amphiphilic copolymers depends on membrane thickness, revealing a nearly quadratic scaling that informs the design of biomimetic membranes.

Contribution

It provides experimental data on the scaling of membrane bending rigidity with thickness for copolymer bilayers, extending traditional surfactant theories to larger, polymer-based membranes.

Findings

Bending rigidity scales nearly quadratically with membrane thickness.

Copolymer membranes are significantly thicker and larger in molecular weight than lipid membranes.

Results support existing theories and aid in designing biomimetic soft interfaces.

Abstract

The bending rigidity $k_c$ of bilayer vesicles self-assembled from amphiphilic diblock copolymers has been measured using single and dual-micropipet techniques. These copolymers are nearly a factor of 5 greater in hydrophobic membrane thickness $d$ than their lipid counterparts, and an order of magnitude larger in molecular weight $\bar{M}_n$. The macromolecular structure of these amphiphiles lends insight into and extends relationships for traditional surfactant behavior. We find the scaling of $k_c$ with thickness to be nearly quadratic, in agreement with existing theories for bilayer membranes. The results here are key to understanding and designing soft interfaces such as biomembrane mimetics.