Donor-acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light-activated photochromes and DASA-functionalized polymers hold great promise as biocompatible photoresponsive materials. However, the photoswitching performance of DASAs in solid polymer matrices is often low, particularly in materials below their glass transition temperature. To overcome this limitation, DASAs are conjugated to polydimethylsiloxanes which have a glass transition temperature far below room temperature and which can create a mobile molecular environment around the DASAs for achieving more solution-like photoswitching kinetics in bulk polymers. The dispersion of DASAs conjugated to such flexible oligomers into solid polymer matrices allows for more effective and tunable DASA photoswitching in stiff polymers, such as poly(methyl methacrylate), without requiring modifications of the matrix. The photoswitching of conjugates with varying polymer molecular weight, linker type, and architecture is characterized via time-dependent UV-vis spectroscopy in organic solvents and blended into polymethacrylate films. In addition, DASA-functionalized polydimethylsiloxane networks, accessible via the same synthetic route, provide an alternative solution for achieving fast and efficient DASA photoswitching in the bulk owing to their intrinsic softness and flexibility. These findings may contribute to the development of DASA-functionalized materials with better tunable, more effective, and more reversible modulation of their optical properties.

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Being amphiphilic lipids, these digestion products can selfassemble into a variety of lamellar and non-lamellar lyotropic liquid crystalline structures attractive for drug and nutrient delivery applications. [9] The dynamic composition of the lipolysis products during triglyceride digestion has a profound influence on the physicochemical properties of the colloidal structures. For example, surface-active lipolysis products can alter the interface of the emulsion particles and transfer water into the triglycerideoil phase. [10] They can further regulate the digestion process by competing with the lipase for the oil-water interface. [11] Their adsorption to the oil-water interface modifies the interfacial tension which, together with shear forces in the digestive tract, can further reduce the emulsion droplet size. The resulting increase in surface area for lipases to access their substrate can ultimately increase the digestion kinetics. Therefore, understanding the structure and properties of these biologically important systems contributes to the development of smarter food materials, which are of great interest for the food industry. [12] In addition to compositional changes, food colloids are also exposed to varying pH and ionic strength conditions as they travel along the digestive tract. While pH in the stomach can be very acidic, intestinal pH can reach alkaline pH values, with this broad pH range being one of the challenges of oral delivery of nutrients and drugs. [13,14] Such changes in the local microenvironment influence the ionization state of the carboxyl group of fatty acids. This modifies their solubility in aqueous media or in the hydrophobic interiors of the emulsion droplet, changing its interfacial properties and their potential to self-assemble into nanostructures. [15][16][17][18][19] The ionization state of acids at a given pH, however, is not exclusively dependent on their molecular structure. While the pK a of an isolated carboxyl group of monomeric fatty acid in water is 4.75, [20] different values are reported in literature for the apparent pK a of acids in self-assembled systems, strongly affected by a variety of parameters such as intermolecular interactions, presence of neighboring charges, dielectric constant, and ionic strength. [16,19,21,22] Therefore, these external parameters can indirectly affect the physicochemical properties of dispersions containing molecules that can be deprotonated. For the case of oleic acid (OA) in particular, reported values of apparent pK a at different conditions and environments range from 6.1 to 9.4. [16,19,23,24] Stimuli-responsive nanostructured emulsions can be utilized to innovate tailor-made materials in fields including biotechnology and food materials. This study reports the composition and pH-responsive colloidal and interfacial properties of the naturally abundant oleic acid-triolein-water emulsions, and applies the knowledge to the sustainable design of nanoemulsions. Small angle X-ray scattering, spinning drop tensiometry, multi-angle dynami...

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