Effect of Synthetic Parameters on Molecular Architecture and Adhesive Performance for Acrylic Emulsion Copolymers

It is well known that both the composition and architecture of a polymer affect its performance as a pressure sensitive adhesive (PSA). However, the specific relationships of glass transition temperature (T_g), degree of branching, crosslinking density, and molecular weight with PSA properties are often complicated, and the variables can be difficult to isolate. Here we present a study examining the effects of acrylic monomer, feed time, and styrene content on the molecular architecture of emulsion-based copolymers with systematically varied composition, and their relationships with adhesive performance. The polymer architecture is elucidated using dynamic mechanical analysis (DMA), gel permeation chromatography (GPC), gel fraction/swell ratio (GF/SR), and ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that the primary acrylic monomer had the most significant effect on polymer architecture, followed by styrene content, and then feed time. The resulting impact on adhesive and cohesive strength will also be discussed.