(33g) Unraveling the Role of Compositional Drifts on the Viscoelasticity and Tack of Pressure-Sensitive Adhesives

Pressure-sensitive adhesives (PSAs) pervade electronic, automobile, packaging, and biomedical applications because they can stick to numerous surfaces without undergoing chemical reactions. Typically, these materials are synthesized by free radical copolymerization of alkyl acrylates and acrylic acid, and, as a result, they comprise an ensemble of polymer chains of varying compositions and molecular weights.

In this talk, I will discuss the use of RAFT copolymerizations in a semi-batch reactor to tailor the molecular architecture (i.e., comonomer sequence), and the linearly and non-linearly viscoelastic properties of acrylic copolymers. The key result is that in the absence of crosslinks, the localization of acrylic acid along the chains leads to microphase separation, creep resistance, and enhanced tack. However, in the presence of Al(acac)₃ and metal-ligand interactions, the localization of acrylic acid along the chains is inconsequential for the creep resistance while significantly affecting the large-strain mechanical properties. This behavior is attributed to microphase separation, but also to a change in the energy required to break metal-ligand associations, and untangle and elongate associative polymers to large deformations.