Poroelasticity of bottlebrush and linear polymer networks

TL;DR

This study compares solvent transport in linear and bottlebrush polymer networks, revealing how network architecture influences permeability and offering insights for designing advanced permeable materials.

Contribution

It demonstrates how bottlebrush network architecture affects permeability and provides experimental data matching theoretical predictions, advancing understanding of solvent transport in complex polymer networks.

Findings

Permeability scales with crosslink density and polymer volume fraction.

Bottlebrush networks show lower permeability scaling exponent than linear networks.

Permeability data collapse onto a single curve when plotted against dry shear modulus.

Abstract

The transport of solvent molecules through soft, swollen networks is critical in both natural and engineered systems. While this poroelastic flow has traditionally been explored in networks where the mesh size is comparable to the solvent molecule size, the effect of network architecture on permeability remains underexplored. Here we investigate solvent transport in linear polymer networks (LPN) and highly elastic bottlebrush elastomer networks (BBN), where the presence of densely grafted sidechains allows for control over swelling and mechanical properties. By synthesizing BBNs with systematically varied crosslinking density while maintaining constant sidechain length and grafting density, we probe the poroelastic response in the stretched backbone regime (SBB). Poroelastic relaxation indentation experiments, performed in toluene, reveal how permeability scales with crosslink density and polymer volume fraction. Compared to LPN with identical chemistry, the BBN exhibited a lower permeability scaling exponent with polymer volume fraction that closely matches the theoretical exponent. Despite architectural differences, permeability data for both networks collapse onto a single curve when plotted against dry shear modulus. Our findings demonstrate that molecular network architecture significantly influences permeability, offering new routes to tailor solvent transport in soft, swollen networks. These insights highlight BBNs as a promising platform for applications in permeable membranes, filtration, and microfluidic systems, and pave the way for further studies on how network parameters, such as sidechain length, impact permeability in these highly tunable materials.