Abstract. Waterborne polyurethane-acrylic hybrid nanoparticles for application as pressuresensitive adhesives (PSAs) were prepared by a one-step miniemulsion polymerization. The addition of polyurethane into a standard waterborne acrylic formulation results in a large increase of the cohesive strength and hence a much higher shear holding time (greater than seven weeks at room temperature), which is a highly desirable characteristic for PSAs. However, with the increase in cohesion, there is a decrease in the relative viscous component, and hence there is a decrease in the tack energy. The presence of a small concentration of methyl methacrylate (MMA) in the acrylic copolymer led to phase separation within the particles and created a hemispherical morphology. The tack energy was particularly low in the hybrid containing MMA because of the effects of lower energy dissipation and greater crosslinking. These results highlight the great sensitivity of the * Corresponding author. E-mail: j.keddie@surrey.ac.uk. Tel +44-1483-686803; Fax +44-1483- 686781.Published in Langmuir (2011) 27(7) pp 3878-3888 2 viscoelastic and adhesive properties to the details of the polymer network architecture and hence to the precise composition and synthesis conditions.

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