posted on 2022-01-20, 23:15authored byMarzieh Mirzamani, Robert C. Reeder, Cassandra Jarus, Vinod Aswal, Boualem Hammouda, Ronald L. Jones, Edward D. Smith, Harshita Kumari
Perfume
mixtures contain perfume raw materials (PRMs) with varying
structures and hydrophobicities, which influence PRM localization
within a surfactant-based formulation and thereby affect the phase
behavior. In rinse-off products, the addition of water can further
affect the phase behavior. In this study, a mixture of 12 PRMs was
used as the oil phase in an aqueous system consisting of sodium trideceth-2
sulfate as a primary surfactant, cocamidopropyl betaine as a cosurfactant,
and dipropylene glycol as a cosolvent. A series of phase diagrams
were constructed with increasing water content, simulating the use
conditions for rinse-off products, to determine how the phase boundaries
shift with dilution. Using these phase diagrams, the compositions
of interest in the micelle without perfume, micelle with perfume,
microemulsion, and micelle–microemulsion transition regions
were identified at each dilution level. The structural changes were
probed through combined small-angle neutron scattering (SANS) and
cryo-transmission electron microscopy analyses. The SANS results showed
that ellipsoidal micelles were maintained as the perfume content and
the dilution level increased. With ≥50 wt % water, increasing
the perfume content increased the micelle volume. Interestingly, a
higher rate of volume increase was observed at ≥70 wt % water.
Notably, the volumes of the micelles with and without perfume increased
steadily with dilution, whereas the volumes of the assemblies in the
transition region and the microemulsion region increased more rapidly
once diluted to 70 and 80 wt % water, respectively.