A pH-responsive fragrance release system based on pseudopeptide polymeric micelles

Controlled release of spices has always been an important subject in the fragrance and flavor industry. In this work, a kind of amphiphilic poly(2-oxazoline)s with pendant Schiff base residues in the hydrophobic segment was designed and synthesized as a potential delivery system for the pH-sensitive release of aldehyde/ketone fragrances in applications of functional perfumery. The aldehyde contents of 0.65-1.74 mmol/g were reached for polymer-fragrance conjugates. Upon direct dissolution in water, polymers self-assembled into micelle-type aggregates with hydrodynamic diameters ranging from 55 to 250 nm. The release kinetic experiments showed that the aroma-carrying nanoparticles exhibited improved stability toward hydrolysis compared to the corresponding non-micellar system. At acidic pH, the imine linkages in the polymers were gradually hydrolyzed and an increasing amount of the aldehyde was released over time. Furthermore, the pseudopeptide pro-fragrances displayed a high affinity to the cotton surface due to the presence of tertiary amide backbones and protonated amino groups in the polymeric matrices.