Tailoring fully biobased optical adhesives via hydrogen-bonding modulation

Display technologies require optical adhesives that simultaneously provide high optical clarity, refractive index control, low birefringence and adhesive strength. However, many commercial adhesive systems rely on petroleum-derived acrylates and isocyanate-based urethanes. Herein, a fully biobased optical adhesive is reported that exploits the initiator-free photopolymerization of dithiolanes. Furthermore, hydrogen bond strength is modulated within the prepared adhesives by changing the chemistry with which the dithiolane is conjugated to a macromolecular core, allowing manipulation of properties including glass transition temperature, adhesion, refractive index, and other optical properties. Throughout these variations, all materials maintain high optical performance, exhibiting visible light transmittance above 98% and haze below 0.7%, coupled with low optical dispersion. These results demonstrate that dithiolanes are readily applied as initiator-free crosslinkers for the formulation of fully biobased optical adhesives.