Cross-Link Location Influences Performance in Acrylic Pressure-Sensitive Adhesives

The influence of network topology on adhesive performance is reported by leveraging the controlled synthesis of polymers with precisely placed cross-linking sites. Copolymers based on n-butyl acrylate and acrylic acid were synthesized using reverse addition–fragmentation chain-transfer (RAFT) polymerization to define the placement of active esters at (1) both chain ends, (2) the center of the backbone, or (3) statistically distributed throughout. After displacement of the active esters with a norbornene-functionalized amine and UV-initiated cross-linking via thiol–ene click chemistry, the properties of each adhesive were compared by 180° peel (adhesive) and lap shear (cohesive) tests. Localizing cross-link points at both chain ends or the center of the backbone improved adhesive properties significantly compared to the statistical copolymer. In summary, these insights suggest new strategies for designing adhesives with tunable and enhanced properties.