Developing Multi Stimuli‐Responsive Core/Shell Microcapsules to Control the Release of Volatile Compounds

Abstract

Encapsulation of 2‐oxoacetates into poly(urea‐urethane) core/shell microcapsules allows the light‐induced controlled release of volatile compounds such as fragrances, plant volatiles, pheromones, or other semiochemicals. On exposure to UVA light, 2‐oxoacetates decompose to form a carbonyl compound together with CO2 or CO, which can build overpressure inside the capsules that expands and/or cleaves the capsule wall to release its content. The influence of the structure and ratio of the polyisocyanates and diamines used for interfacial polymerization, as well as the composition of the capsule wall and the oil phase, are investigated by dynamic headspace analysis of the released volatile compounds to optimize the performance of the delivery system. The combination of a light‐induced release with the mechanical cleavage of the capsule gives access to multi stimuli‐responsive systems that selectively respond to the different triggers applied. Furthermore, the concept outlined in the present work is generally applicable to other photolabile precursors that generate a gas inside the capsules and thus release co‐encapsulated active molecules as a direct response to light.

Preparation of Cinnamon Oil‐Loaded Antibacterial Composite Microcapsules by In Situ Polymerization of Pickering Emulsion Templates

“…[ 17–19 ] Microcapsule formation allows protecting the core materials by inhibiting their volatilization and preventing their chemical deterioration, and can also control the release behaviors of core materials. [ 20–22 ] Thus, the trapping and loading of CMO into microcapsules is a promising strategy to solve the easy volatility and high vulnerability problems of CMO. To date, a wide variety of techniques have been proposed for the fabrication of the essential oil–loaded microcapsules, such as spray drying, [ 23 ] coacervation, [ 24 ] coaxial electrospray, [ 25 ] Pickering emulsion templates, [ 26 ] and layer‐by‐layer assembly.…”

Quantification of Residual Perfume by Py-GC-MS in Fragrance Encapsulate Polymeric Materials Intended for Biodegradation Tests

“…Core shell microcapsules containing fragrance oil were prepared according to literature procedures [10,12,23].…”

“…Different delivery systems have been developed across the years, notably in order to control the kinetic release of odorant molecules, increase storage stability and/or improve deposition on different substrates [4][5][6][7]. Core-shell microcapsules are the most used, thanks to the possibility of perfume release as a result of an external stimulus, e.g., mechanical rubbing [8][9][10], light exposure [11][12][13] temperature [14,15] or pH change [16][17][18]. They consist of a spherical shell of cross-linked polymer (e.g., polyurea, polyurethane, melamine-formaldehyde, polyamides, etc.)…”

Encapsulation of Flavours and Fragrances into Polymeric Capsules and Cyclodextrins Inclusion Complexes: An Update

“…Particularly, polymers both of natural or synthetic origin have been reported to successfully encapsulate flavour and fragrances into single or multi-layered core-shell micro- or nanocapsules [ 16 , 17 , 18 ]. These capsules resulted in being highly versatile for the encapsulation of volatile compounds, thanks to the large variety of polymers and methodologies available (e.g., coacervation and interfacial polymerisation), through which their chemical–physical properties can be tuned [ 19 , 20 ]. Therefore, polymeric capsules can provide an easy handling and processing of this class of chemical compounds, guaranteeing, at the same time, a satisfactory protection from evaporation or degradation, good mechanical properties and the possibility of modulating or controlling the release at different conditions [ 21 ].…”