Adhesive properties of a radial acrylic block co-polymer with a rosin ester resin

A novel four-arm radial block co-polymer (A-B)(4) obtained by atom transfer radical polymerization (ATRP) and a random (statistical) co-polymer of similar composition have been prepared. In the presence of rosin esters, these materials show pressure-sensitive adhesive (PSA) properties. The aim of this investigation was to study the relationship between the molecular architecture of tackified systems and their typical PSA properties. First, the miscibility of these two co-polymers with a rosin ester resin was investigated. Then, the performance of PSA such as peel strength and shear resistance was studied. In contrast to the random co-polymer, the block copolymer presents two glass transitions, as evidenced by DSC and TMA. Atomic force microscopy (AFM) further confirmed the well-defined microphase separation. The Gordon-Taylor expression provides an empirical description of the dependence of the T-g on the tackifier content for the random co-polymer and the elastomer phase of the block co-polymer. The DSC results also suggest that the thermoplastic microdomains are partly miscible with the tackifier. In terms of PSA properties, it was observed that the peel strength was improved as the amount of tackifer in the blend was increased. Although the addition of rosin ester led to a significant drop of the cohesive strength of the random copolymer, the network present in the block co-polymer made it possible to reach the required cohesion for suitable adhesive performance in PSAs.