“Old” chemistry in a new context: photocleavable 2-oxoacetate-containing latex dispersions and core–shell microcapsules for the controlled release of volatile compounds

Abstract

Natural daylight is suitable for controlling the release of volatile compounds, such as fragrances, from different surfaces. Upon UVA irradiation, 2-oxoacetates (α-ketoesters) fragment in a Norrish type II reaction to form aldehydes and ketones. To profit from the stabilising effect of polymers in an aqueous environment, we extended our previous work on 2-oxoacetate profragrances to two alternative polymeric delivery systems. We thus compared the light-induced release of fragrance aldehydes from 2-oxo-2-phenylacetates encapsulated into melamine-formaldehyde core-shell microcapsules, on the one hand, with latex nanoparticle dispersions obtained by radical (co-)polymerisation of fragrance-releasing 2-oxo-2-(4-vinylphenyl)acetate monomers, on the other hand. We could demonstrate that microcapsules prepared with a minimum amount of resin in their shell performed best, while the size of the latex nanoparticles influenced the deposition of the delivery systems from aqueous media onto the target surface. Furthermore, dynamic headspace analysis above cotton showed that both systems are alternative and reliable techniques to control the light-induced delivery of fragrances in practical applications under natural daylight conditions.

Polystyrene‐Based 2‐Oxoacetates for the Light‐Induced Release of Fragrances Under Realistic Application Conditions

“…A few systems that combine the two approaches, namely by encapsulating profragrances, have also been reported. [ 3–5 ]…”

“…Environmental conditions that allow the cleavage of covalent bonds, and that have been studied for the controlled release of fragrances from polymeric profragrance conjugates, are mostly based on hydrolysis, e.g., of imines, [ 7 ] linear or cyclic acetals, [ 8,9 ] and a few other structures; [ 10 ] on retro‐1,4‐additions; [ 11,12 ] and, less frequently, on the action of enzymes [ 13 ] or light. [ 3,9 ] The light‐induced release of fragrances from polymeric (or non‐polymeric) profragrances is particularly interesting because perfumes evaporate from surfaces that are typically exposed to (sun)light. [ 14 ] On the other hand, premature degradation of the precursors during storage can be avoided with the use of opaque packing materials.…”

“…[ 16 ] We have also studied the fragrance release from polymeric 2‐oxoacetate‐based delivery systems by comparing the release from profragrance conjugates with that from encapsulated profragrances ( Scheme ). [ 3,4 ] From an application standpoint, capsules have the advantage of being able to release mixtures of fragrances (perfumes), whereas profragrances (especially non‐polymeric) often release only a single fragrance molecule. Although polymer conjugates can be easily designed to simultaneously release several perfumery materials from the same polymer backbone, previous studies on polymer conjugates essentially focused on the controlled release of single‐fragrance molecules.…”

“…Although polymer conjugates can be easily designed to simultaneously release several perfumery materials from the same polymer backbone, previous studies on polymer conjugates essentially focused on the controlled release of single‐fragrance molecules. [ 3,7–13 ]…”

Advances in preparation and controlled release of profragrances under ambient conditions

“…General principles for the controlled release of fragrances from 2-nitrobenzyl compounds, and chemical structure of profragrance 16 [30~34].图 12 α-酮酯类潜香体光控释放醛酮类香料的原理及相应 潜香体17、18以及形成的核壳微胶囊和纳米颗粒的结 构[10,35] Photolysis of 2-oxoacetates to release carboxides, and chemical structures of profragrances 17 and 18 including their coreshell microcapsule and latex nanoparticle structure[10,35].…”