Controlling the Friction of Gels by Regulating Interfacial Oxygen During Polymerization

Rok Simič,Nicholas D Spencer

doi:10.1007/s11249-021-01459-1

Abstract

Hydrogel surfaces are of great interest in applications ranging from cell scaffolds and transdermal drug-delivery patches to catheter coatings and contact lenses. In this work, we propose a method to control the surface structure of hydrogels, thereby tailoring their frictional properties. The method is based on oxygen inhibition of the free-radical polymerization reaction during synthesis and enables (i) control of friction over more than an order in magnitude and (ii) spatial control of friction as either a continuous gradient or a distinct pattern. The presented method has successfully been applied to acrylamide-, diacrylate- and methacrylate-based gels, illustrating the universality of the presented method, and its potential use in the above-mentioned applications.Graphical

Highlights

Hydrogels, with their cross-linked polymer network and large water content, share many structural similarities with biological tissues
We present a method that enables the amount of oxygen delivered to the mold-solution interface to be controlled during radical polymerization, allowing hydrogel friction to be fine-tuned within a range that spans more than one order of magnitude
The force-indentation curves shown in Fig. 4a were obtained for PAAm hydrogel surfaces synthesized against a thin PE membrane while using different amounts of molecular oxygen in the source gas

Summary

Introduction

With their cross-linked polymer network and large water content, share many structural similarities with biological tissues. The oxygen inhibition of radical polymerization at the interface results in incomplete network formation, creating a sparse, water-rich surface region with a high concentration of dangling chains. Such surfaces have been shown to exhibit up to an order of magnitude lower friction compared to hydrogels with a uniform level of crosslinking from the bulk to the surface [14, 15]

Methods

Results

Conclusion