Oligomerising biomimetic UV filters for next-generation sunscreens

para-Coumaric acid (pCA), a naturally occurring ultraviolet (UV) filter, was oligomerised to form its trimer, 3pCA, to explore its potential application for sunscreen photoprotection. 3pCA's photophysical and photochemical properties following the absorption of solar radiation were investigated through steady-state and ultrafast transient absorption spectroscopic methods. The results presented here imply a network of three largely independent pCA-like chromophore units within the whole molecular structure, that each utilise the isomerisable CC double bond to facilitate ultrafast non-radiative decay. Complementing these ideal photodynamical properties, the oligomerisation additionally reduces solubility in many common organic solvents, opening the door for enhanced photoprotection through UV light scattering from aggregates, and brings the molecular weight closer to the 500 Daltons threshold suggested to minimise transcutaneous penetration. Altogether, this study demonstrates oligomerisation as an auspicious design principle for next-generation sunscreens.