Abstract
A pressure-sensitive adhesive (PSA) requires only the application of light pressure to form a bond with a surface. PSAs rely on a balance of viscous and elastic properties in order to attain a high energy of separation from the surface. Their properties are tuneable through molecular architecture, as well as through the creation of composite materials. Herein, several methods for tuning the adhesive and mechanical properties of waterborne PSAs are presented. New methods for achieving one-way switchable adhesion and patterned adhesive surfaces are proposed. Nanoparticles with a high glass-transition temperature (Tg) are used to adjust the adhesive properties of a standard poly(butyl acrylate) (PBuA) PSA, creating anisotropic optimised adhesive nanocomposites which also display a switch-off of adhesion after heating. The phenomenon is refined to facilitate a switch-off of adhesion in 30 seconds, and leads to the possibility of patterned adhesive surfaces by infrared heating of masked nanocomposites. The function of poly(acrylic acid) (PAA) in a waterborne PSA is also studied. The relationship of PAA content and its location within, or adsorbed on, the particles is explored. The pH sensitivity of materials containing PAA is exploited to optimise various soft PSAs for good adhesion. The adhesive and mechanical properties of novel soft-soft core-shell polymers, made via the first use of poly(2-diethylaminoethyl acrylate) (PDEAEA) in PBuA-based adhesive formulations, are studied. A unique debonding mechanism is characterised and found to be caused by residual oligomer. The system is then used to re-create the novel mechanism in a model PSA. Using the criteria set out in the literature review, a comprehensive set of techniques, including probe-tack adhesive testing, mechanical property studies, and surface analysis, are used to characterise these materials and to explain the relationship between their mechanical and adhesive properties. Methods for optimising their properties are presented.