Impact of model 7-perfume molecule accord on the self-assembly of branched mixed-surfactant system as a function of dilution and dipropylene glycol: A neutron scattering study
Podium 43
Presented by: Harshita Kumari
Introduction: Perfumes and flavors are very essential ingredients that impact consumer perception. The industry relies on perfumers or flavorist to assess the performance of a product. The challenge lies in discerning how complex perfume molecules partition within colloidal domains owing to the number of perfume raw materials (PRM) used in one perfume composition. Herein, we have studied the structure of a mixed-surfactant system comprising a 7-PRM mixture. Specifically, we look at the effect of dilution and dipropylene glycol on the structure of micelle using small-angle neutron scattering/SANS.
Methods: Five samples were prepared each comprising varying percentages of sodium trideceth-2 sulfate (ST2S), cocamidopropyl betaine (CAPB), the cosolvent dipropylene glycol (DPG); citric acid; the 7-PRM perfume accord (phenylethyl alcohol, benzyl acetate, methyl dihydrojasmonate, dihydromercenol, hexylcinnamic aldehyde, linalool, linalyl acetate). All materials were provided by Procter & Gamble (Cincinnati, OH). It should be noted that these materials are the same industrial-grade materials used by P&G in product manufacturing. These materials were used so that the results would be more representative of an actual formulation.
Each sample was loaded into a titanium cell holder with quartz windows set 1 mm apart, for a 1 mm sample thickness. Samples were prepared in deuterated water to provide sufficient contract in neutron scattering. SANS study was conducted at Oak Ridge National Laboratory, which was set at two different detector distances and one neutron wavelength to achieve the desired q-range. The low-q SDD (sample to detector distance) was 5.2 m, while the wavelength was 5 Å. For high-q, the SDD was 1.2 m with a 5 Å neutron wavelength. These settings gave a q-range of 0.006752 Å-1 to 0.5455 Å-1. The resulting data from each instrument configuration was reduced by correcting for background scattering, determining the transmission ratios, and performing a circular average using the reduction macros in Igor Pro. The data from both configurations for each sample were then combined to form a single data set spanning the entire q-range.
Results: The data were analyzed in SasView version 5.0.3 using the smeared Uniform Ellipsoid form factor with the Screened-Coulomb structure factor model. The Uniform Ellipsoid form factor model is averaged over all orientations of particles and is normalized by the particle volume, Vell. The results show that the addition of DPG showed a decrease in both Ra and Rb of ellipsoidal geometry. The volume of micelle showed a decrease from 68582 Å3 to 52169 Å3; however, the volume fraction remained the same which indicates the presence of more micelles in the presence of DPG. The dilution from 2:1 (Ra=29.34 Å; Rb=15.82 Å) to 5:1 (Ra=42.06 Å; Rb=17.24 Å) shows an increase in micelle size but a decrease in volume fraction suggesting that micelles break down upon dilution and releases perfume.
Discussion: We earlier reported a 3-PRM and 12-PRM accord and the effect of dilution on surfactant self-assembly. Unlike, these accords our 7-PRM comprises linalool and linalyl acetate. The only other two studies reported comprising of linalool were those with Penfold wherein he observed lamellar phases. Herein, the 7-PRM accord for the mixed-surfactant system reveals the presence of an ellipsoidal geometry. Interestingly, the volume of the 7-PRM accord with DPG is 1.5 times lower than that of a 12-PRM accord at comparable dilution and perfumer to surfactant ratio. Similarly, a 1.3 times lower micellar volume is observed for a 7-PRM accord than a 12-PRM accord. This observation is consistent with our earlier reported localization of PRMs within the micellar core.
Conclusion: In conclusion, we report the effect of hydrotropes /DPG and dilution on a branched mixed-surfactant system comprising of a 7-PRM accord. Uniquely, this accord comprises multiple ingredients, especially linalool and linalyl acetate which are otherwise studied singly. The results suggest unique structural features for a mixed accord which were not observed earlier when studied singly. The study further reinforces how 7-PRM vs. 3-PRM vs. 12 PRM compares and how trends in their micellar sizes and volumes are dependent on the localization of PRMs within the formulation.
Methods: Five samples were prepared each comprising varying percentages of sodium trideceth-2 sulfate (ST2S), cocamidopropyl betaine (CAPB), the cosolvent dipropylene glycol (DPG); citric acid; the 7-PRM perfume accord (phenylethyl alcohol, benzyl acetate, methyl dihydrojasmonate, dihydromercenol, hexylcinnamic aldehyde, linalool, linalyl acetate). All materials were provided by Procter & Gamble (Cincinnati, OH). It should be noted that these materials are the same industrial-grade materials used by P&G in product manufacturing. These materials were used so that the results would be more representative of an actual formulation.
Each sample was loaded into a titanium cell holder with quartz windows set 1 mm apart, for a 1 mm sample thickness. Samples were prepared in deuterated water to provide sufficient contract in neutron scattering. SANS study was conducted at Oak Ridge National Laboratory, which was set at two different detector distances and one neutron wavelength to achieve the desired q-range. The low-q SDD (sample to detector distance) was 5.2 m, while the wavelength was 5 Å. For high-q, the SDD was 1.2 m with a 5 Å neutron wavelength. These settings gave a q-range of 0.006752 Å-1 to 0.5455 Å-1. The resulting data from each instrument configuration was reduced by correcting for background scattering, determining the transmission ratios, and performing a circular average using the reduction macros in Igor Pro. The data from both configurations for each sample were then combined to form a single data set spanning the entire q-range.
Results: The data were analyzed in SasView version 5.0.3 using the smeared Uniform Ellipsoid form factor with the Screened-Coulomb structure factor model. The Uniform Ellipsoid form factor model is averaged over all orientations of particles and is normalized by the particle volume, Vell. The results show that the addition of DPG showed a decrease in both Ra and Rb of ellipsoidal geometry. The volume of micelle showed a decrease from 68582 Å3 to 52169 Å3; however, the volume fraction remained the same which indicates the presence of more micelles in the presence of DPG. The dilution from 2:1 (Ra=29.34 Å; Rb=15.82 Å) to 5:1 (Ra=42.06 Å; Rb=17.24 Å) shows an increase in micelle size but a decrease in volume fraction suggesting that micelles break down upon dilution and releases perfume.
Discussion: We earlier reported a 3-PRM and 12-PRM accord and the effect of dilution on surfactant self-assembly. Unlike, these accords our 7-PRM comprises linalool and linalyl acetate. The only other two studies reported comprising of linalool were those with Penfold wherein he observed lamellar phases. Herein, the 7-PRM accord for the mixed-surfactant system reveals the presence of an ellipsoidal geometry. Interestingly, the volume of the 7-PRM accord with DPG is 1.5 times lower than that of a 12-PRM accord at comparable dilution and perfumer to surfactant ratio. Similarly, a 1.3 times lower micellar volume is observed for a 7-PRM accord than a 12-PRM accord. This observation is consistent with our earlier reported localization of PRMs within the micellar core.
Conclusion: In conclusion, we report the effect of hydrotropes /DPG and dilution on a branched mixed-surfactant system comprising of a 7-PRM accord. Uniquely, this accord comprises multiple ingredients, especially linalool and linalyl acetate which are otherwise studied singly. The results suggest unique structural features for a mixed accord which were not observed earlier when studied singly. The study further reinforces how 7-PRM vs. 3-PRM vs. 12 PRM compares and how trends in their micellar sizes and volumes are dependent on the localization of PRMs within the formulation.