Abstract
The encapsulation of poorly water-soluble compounds such as perfumes, flavors, and bioactive molecules is a key step in the formulation of a large variety of consumer products in the fields of household care and personal care. We study the encapsulation ability of an amphiphilic poly(ethylene glycol)-graft-poly(vinyl acetate) (PEG-g-PVAc) graft copolymer, extending the focus to the entire phase diagram of polymer/perfume/water systems with three common natural fragrances. The three perfume molecules (2-phenyl ethanol, L-carvone, and α-pinene) possess different water affinities, as expressed by their octanol/water partition coefficients. The investigation of the polymorphism of PEG-g-PVAc in these systems is carried out by means of dynamic light scattering, small-angle X-ray scattering, NMR spectroscopy, and confocal laser scanning microscopy. The results presented here demonstrate that the choice of fragrance can dramatically affect the supramolecular structures formed by the polymer in aqueous solution, with important consequences on formulations of industrial interest such as the demixing of complex perfume blends when one or more of the components have no chemical affinity for any of the polymer blocks.
Highlights
The encapsulation of poorly water-soluble compounds such as perfumes, flavors, and bioactive molecules is a key step in the formulation of a large variety of consumer products.[1]
In our previous investigation of dilute aqueous Poly(ethylene glycol) (PEG)-gPVAc,[21] we demonstrated the formation of globular singlechain nanoparticles (SCNPs) at a low polymer concentration (
To evaluate the possible behavior of the PEG-g-poly(vinyl acetate) (PVAc) polymer in the presence of each perfume, we first performed solubility tests with the simple polymers PEG and PVAc (6 and 7 kDa, respectively). 2-Phenyl ethanol behaved as a good solvent for PEG and a poor solvent for PVAc; carvone was a poor solvent for PEG and a good solvent for PVAc; pinene was a bad solvent for both
Summary
The encapsulation of poorly water-soluble compounds such as perfumes, flavors, and bioactive molecules is a key step in the formulation of a large variety of consumer products.[1]. Due to the complexity of typical matrices in cosmetics and cleaning agents, the formulation of valuable encapsulation systems entails a compromise of several qualities: good mechanical properties, stability (shelf life), controlled release, low toxicity of both precursors and finished product, biodegradability, cost-effective materials and processes, and scalable methods for industrial production. Nano- and microencapsulation systems such as micelles and liquid crystals based on nonionic block copolymers are typically very stable both thermodynamically and kinetically.[16,17] Thanks to their solvent-selective blocks, these polymers are amphiphiles and they can form a whole range of supramolecular self-assembled structures common to smallmolecule surfactants,[18] which can be profoundly affected by the presence of encapsulated chemicals.[19] It is essential to understand the interactions existing between
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