Sunlight Activated, Film Forming Polymer Based on Diazirine Grafted Polycaprolactone

Diazirine-grafted polycaprolactone adhesive, CaproGlu, can be photoactivated using sunlight as a stimulus and shows the potential of a film-forming sunscreen or a component thereof. Herein, the structure-property relationships of molecular weight, activation temperature, and inclusion of a photocatalyst on the film-forming capabilities of CaproGlu are investigated. Using polycaprolactone of molecular weight 1000 Da allows for a non-inferior storage modulus and elasticity compared to a paste-like formulation while retaining the fluidity required for easy spreading. Increasing the activation temperature of CaproGlu results in lower viscosity and requires a larger dosage of light energy for gelation. The inclusion of an iridium photocatalyst allows for faster photoactivation kinetics with non-inferior rheological properties compared to controls. Preliminary skin sensitization assays show negative results for both CaproGlu and IrPC formulations, supporting the potential for topical usage.