Mechanical reinforcement and property tuning of adhesive elastomers with polymer-grafted inorganic nanoparticles

Abstract

Pressure-sensitive adhesives are a ubiquitous class of soft elastomer adhesives capable of instantaneous bonding to a substrate under light pressure. However, their viscoelastic nature renders them vulnerable to mechanical destruction, degradation, and creep, limiting their application window. Established methods for strengthening the PSA film have relied on stiffening the adhesive component, either by increasing network density via crosslinking bonds or addition of immobilizing filler particles. The result is a decrease in adhesive power, further limiting their utility as adhesive products, and represents a fundamental tradeoff between network bonding strength and wettability. New strategies for how to increase the effective strength of existing bonding interactions without increasing their number would be of significant interest both for fundamental studies into adhesive nanoscale structure and for applications-driven rational design of materials. In this thesis, we will address this fundamental challenge using multivalent polymergrafted nanoparticles to manipulate the nanoscale structure of the PSA such that strain resisting interactions can be decoupled from flow properties at the bulk scale. A conventional solvent-borne PSA with crosslinking residues was first investigated to understand how multivalent PGNP centers might amplify the effects of crosslinking. Subsequently, a waterborne PSA/water-soluble PGNP methodology was demonstrated to investigate how PGNPs might be used to bridge existing voids in the gel structure of a non-crosslinked adhesive. Lastly, a 3D-printable, solvent-free photocured elastomer resin was prepared with PGNP filler to show how nanocomposite adhesive materials might be processed into functional components and objects beyond simple PSA films. The effects of various structural and compositional parameters of both PSAs and PGNPs on the final mechanical properties of the film are also discussed at length to demonstrate how a design-of-materials strategy can be applied to these nanocomposite systems to prepare PSA materials with designer properties.