# Membranes with artificial free-volume for biofuel production

## TL;DR

This paper introduces a new method to create polymer membranes with adjustable free-volume for better alcohol separation in biofuel production.

## Contribution

A novel method to generate artificial free-volume in polymer membranes using self-assembled triblock copolymers is presented.

## Key findings

- Artificial free-volume improves alcohol permeability in polymer membranes.
- The method allows fabrication of membranes with identical composition but varying free-volume.
- The membranes show enhanced selectivity for alcohol-water separations relevant to biofuels.

## Abstract

Free-volume of polymers governs transport of penetrants through polymeric films. Control over free-volume is thus important for the development of better membranes for a wide variety of applications such as gas separations, pharmaceutical purifications and energy storage. To date, methodologies used to create materials with different amounts of free-volume are based primarily on chemical synthesis of new polymers. Here we report a simple methodology for generating free-volume based on the self-assembly of polyethylene-b-polydimethylsiloxane-b-polyethylene triblock copolymers. We have used this method to fabricate a series of membranes with identical compositions but with different amounts of free-volume. We use the term artificial free-volume to refer to the additional free-volume created by self-assembly. The effect of artificial free-volume on selective transport through the membranes was tested using butanol/water and ethanol/water mixtures due to their importance in biofuel production. We found that the introduction of artificial free-volume improves both alcohol permeability and selectivity.

The free-volume of a polymer is a key parameter in its ability to permit through transport of small molecules. Here, the authors develop a way of introducing different degrees of artificial free-volume to a polymer membrane, and thus tailor its penetrability for applications including biofuel purification.