Direct measurement of the critical pore size in a model membrane

TL;DR

This study measures the critical pore size in a model polymer membrane, revealing how it scales with film thickness and molecular architecture, advancing understanding of pore nucleation and stability.

Contribution

It provides the first direct measurement of the critical pore size in a model membrane and links it to film thickness and molecular architecture effects.

Findings

Critical pore size scales linearly with film thickness.

Pore energy cost is influenced by molecular architecture.

Enhanced pore formation frustration observed in diblock copolymer membranes.

Abstract

We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.