JOURNAL OF COSMETIC SCIENCE 46 Figure 5 shows zero-shear viscosity data for the polyglyceryl methyl glucose dioleate (PGMGD) thickeners as a function of PG repeat unit DP when used at 5 wt% in an adult shampoo surfactant base consisting of ammonium laureth sulfate (ALES), ammonium lauryl sulfate (ALS), and cocamide MEA (CMEA). The data reveal that as the DP of the PG chains initially increases from 4 to 10 repeat units, the viscosity building ability of the molecules increases dramatically however, as the DP increases beyond 10 repeat units, the viscosity building decreases precipitously, and molecules having DP greater than ca. 20 repeat units actual cause the surfactant blend to lose viscosity. This behavior is the result of the changing molecular geometry of the PGMGD with increasing PG DP: as the hydrophilic PG chains of the head group become progressively larger relative to the hydrophobic MGD tail group, the PGMGD will become more hydrophilic and the criti- cal packing parameter (CPP) of the molecule will decrease. The initial increase in hydro- philicity and decrease in CPP enable PGMGD to have favorable solubility in the surfactant system and cause the net radius of curvature in the system to decrease, leading to the formation of longer rod-like micelles and higher viscosities in the surfactant system tested (10). However, as the PG DP continues to increase beyond 10 repeat units, the excess hydrophilicity and continually decreasing CPP will eventually cause the net radius Figure 4. Synthesis of polyglyceryl-n-methyl glucose dioleate via base-catalyzed ring-opening polymeriza- tion of GC initiated by MGD. Figure 5. Zero-shear viscosity data for PGMGD thickeners at in an adult shampoo surfactant base (ALES/ALS/CMEA). PGMGD concentration = 5 wt%.

NEW COSMETIC INGREDIENTS FROM POLYGLYCEROL 47 of curvature to begin increasing, resulting in shorter rod-like micelles and eventually a transition from rod-like to spherical micellar geometry, all of which coincide with the observed decreasing viscosities. Based on these fi ndings, the polyglyceryl polyol ester thickeners are considered to function more effectively as hydrophobic core thickeners and not like highly ethoxylated hydro- philic corona-type thickeners, e.g., PEG-120 methyl glucose dioleate.10 These PG-based thickeners are best suited for surfactant systems that build viscosity via rod-like micelle formation, e.g., blends containing high concentrations of anionic surfactants. The GC polymerization approach enables effective control of the PG DP, in turn offering the potential to synthesize thickeners with CPPs tailored to provide the most effi cient radius of curvature for maximizing rod-like micelle formation in a given surfactant system. CONCLUSION PG is a versatile bio-based platform that can be exploited for the development of a broad range of functional cosmetic ingredients, including surfactants, conditioning agents, and thickeners. When utilized with green chemistry and sustainable design principles in mind, PG offers ingredient manufacturers and formulators yet another alternative to increase biorenewable content in their products without sacrifi cing on functional or aesthetic benefi ts. The synthetic fl exibility of PG ingredient platforms enables ingredients to be tailored to specifi c applications and for maximum performance. REFERENCES (1) M. J. Fevola, Cosmetics & Toiletries, 126(8), 548 (2011). (2) G. Rokicki, P. Rakoczy, P. Parzuchowski, and M. Sobiecki, Hyperbranched aliphatic polyethers obtained from environmentally benign monomer: Glycerol carbonate, Green Chem., 7, 529–539 (2005). (3) J. N. Masci and N. A. Poirier, Detergent compositions, US Patent 3,055, 836 (1962). (4) R. J. Verdicchio and J. M. Walts, High-lathering non-irritating detergent compositions, US Patent 3,950,417 (1976). (5) M. J. Fevola, Compositions comprising a polyglyceryl nonionic surfactant and a zwitterionic surfactant, US Patent 8,227,393 B2, (2012). (6) M. J. Fevola, F. C. Sun, and S. E. York, Cationic polyglyceryl compounds and compositions, US Patent 8,961,945 B2 (2015). (7) S. B. Polovsky, H. L. Moshel, J. P. Pavlichko, and A. Friedman, Alkoxylated alkyl glucoside ether qua- ternaries useful in personal care, US Patent 5,138,043 (1992). (8) H. S. Bevinakatti, A. G. Waite, and J. Frank, Polyglycerol ethers of sorbitan carboxylic acid esters, Patent WO2009016375A2 (2009). (9) S. Andjelic, M. Erneta, M. J. Fevola, and F. C. Sun, Polyglyceryl compounds comprising a methyl glu- coside or sorbitan remnant and compositions comprising the same, US Patent 8,455,418 B2 (2013). (10) U. Kortemeier, J. Venzmer, A. Howe, B. Grüning, and S. Herrwerth, SOFW J., 136(3), 30–38 (2010).