Thermally activated pressure-sensitive adhesives

We describe an approach to form stimuli-responsive pressure-sensitive adhesive ( PSA) films that are activated by thermal energy. This approach is used to form films that do not adhere on contact to any non-adhesive substrates. However, upon activation using heat as a stimulus, the films change irreversibly into PSA coatings. In order to develop this system, a PSA polymer emulsion stabilized by a novel low-molecular-weight polymeric stabilizer was synthesized. This emulsion was dried at ambient conditions to form films with a well-defined morphology with the PSA encapsulated by a protective matrix of polymeric stabilizer. This morphology is not thermodynamically stable and is disrupted when the temperature is elevated above the glass transition temperature of the protective polymeric stabilizer. Thermodynamically-driven rearrangement of the phases leads to the PSA migrating to and occupying the air - film interface. The impact of the amount and composition of the stabilizer in the PSA emulsion on emulsion stability, latency and stimulus response was explored. Supporting data for the proposed mechanism include TEM micrographs of the film morphology.