Natural Product-Based Pressure-Sensitive Adhesives via Carveol-Dithiothreitol Thiol-Ene Step-Growth Polymerization

Pressure-sensitive adhesives occupy a large role in the commercial use of polymers; however, they are typically limited to nondegradable formulations using petroleum-based materials. As the plastic and environmental crises have intensified, the need for renewable starting materials and degradable designs has similarly deepened. With that goal, we endeavored to make adhesive films from renewable terpenes as a safer and more sustainable route to PSAs. Specifically, based on our previous report of the cross-linking ability of a carveol-based carbonate through thiol-ene chemistry, we report further exploration of the adhesive possibilities of this system. A carbonate monomer of dimerized carveol was linearly polymerized with dithiothreitol via UV-initiated thiol-ene chemistry and formed into adhesive coatings, with unmodified geraniol doped in as a tackifier. We obtained a range of adhesive properties based on the ratio of exo-methylene to thiol units and reported on the degradation of the adhesive coatings.