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Designing nanoporosity in a swollen polymer for the controlled release of a highly volatile fragrance

Controlling the fragrance release profile, especially the highly volatile top note, can prolong the desired scent of the fragrance. Here, the porosity of a swollen cross‐linked polyurethane acrylate (PUA) polymer, which is tuned by the length of a modulator, can influence the evaporation rate of the top note. In particular, the evaporation rate of benzyl acetate (BA), a common top note, is reduced by a factor of 6.5 (from 134 to 17 mg m–² min–¹) when BA is released from the best‐performing PUA against a reservoir of BA. The average diameter of an opening in the fragrance‐loaded PUA is ~6 nm, as determined by the thermoporosimetry approach. Such a pore size can effectively control the evaporation rate of BA, as predicted by the theoretical model, which reveals that a pore diameter of <16 nm is required. Computational modelling reveals the optimal chain length for a modulator used for the sustained released of fragrance, confirming the experimental data. Finally, BA continues to be released from the PUA matrix for a prolonged period, even after 3 months, whereas the same quantity of BA would completely evaporate after 1 week in the absence of PUA matrix. Approximately 50wt% of BA remains after 60 days, making it one of the best techniques in sustaining the release of a top note.