EMOLLIENCY AND CHEMICAL SrI'RUCTURE 64l A relatively emollient material, PEG 200 monooleate (whose "work sheet" is shown in Fig. 1), is used to illustrate the complete evaluation procedure. The POLYOL MONOESTERS OF OLEIC ACID, in general, are a uniformly poor group in terms of skin feel (Table III). Only the PEG 200 monooleate (SFI -- 4.0//15.7) gave a decent result. All except PPG 2000 oleate are either water-soluble or water-dispersible (a property which seems to be unfavorable to final skin feel). In this particular series, PEG 200 monooleate gave a considerably better End Feel (15.7) than PPG 2000 monooleate (11.3), even though the latter is not water-soluble. In the case of PPG 2000 monooleate, however, oleic acid represents only 12% of the molecular weight, compared to 54% in PEG 200 monooleate. Ap- parently, greater "oiliness" is favorable to high End Feel scores. If this is true, it may be possible to correlate End Feel with HLB values of emol- lients. The approximate molecular weight of each emollient was determined from saponification values where available, and from the theoretical struc- ture otherwise. The number of carbons in the homolog portion of each series is also shown in the tables. Viscosities of the finished products (7% emollient in "Base Formula") were recorded after each cream or lotion had aged approximately 30 days. HLB, hydroxyl values, per cent branching (7o side chains/total mol wt) and iodine values (degree of unsaturation) were among the other factors considered in attempting to correlate Skin Feel with chemical structure in this initial study. POLYOL POLYESTERS OF OLEIC ACID (Table III) apparently present the same problems as the polyol monoesters of oleic acid. None of them are very good, in spite of their greater molecular weight resulting from esterification of polymerized glycerol. All of these esters formed heavy, pasty, or gelatinous lotions. Polyol esters of fatty acids are not usually used as emollients for this reason they were included in this study only to help find correlations to chemical structure. The greater the water solubility of emollients, the more Initial Slip they give to emulsions containing them and, usually, the poorer the End Feel. In contrast, the oilier they are, the better their End Feel. This will be seen dramatically in the next group of emollients to be considered. FATTY AI.COHOL ESTERS OF OLEIC ACID (Table III) show an immediate improvement in final skin feel over the two series of polyol esters of oleic acid. Even the least efficacious fatty alcohol oleic ester, hexadecyl oleate (End Feel • 13.0), was substantially better than 907o of

642 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Esters of Oleic Acid CHa(CH2)7CH•CH(CH,•)7COOH C•s Acid Mol Wt 276 Polyol Monoesters: Approx Mol wt Polyol Viscosity Carbons (Lotion)(cps) Glyceryl monooleate 350 3 4580 PEG 200 monooleate 506 85= 7810 Triglyceryl monooleatc 498 9 8290 PEG 600 monooleate 863 26-4- 182 PEG 1540 monooleate 1753 69 5= 30 PPG 2000 monooleate 2244 1025= 2560 Polyol Polyesters: Diglyceryl dioleate 682 6 2092 PEG 400 dioleate 916 17 5= 2688 Decaglyceryl tetraoleate 1791 30 7940 Decaglyceryl octaoleate 2822 30 2300 Decaglyceryl decaoleate 3339 30 2180 Fatty Alcohol Esters: (% Branching) n-Decyl oleate Isodecyl oleate Hexadecyl oleate Oleyl oleate Isostearyl oleate Polyol Monoester Skin Feels: Polyol Polyester Skin Feels: Fatty Alcohol Ester Skin Feels: 410 10 5320 ... 410 10 6180 3.6 500 16 5300 17.0 526 18 6860 528 18 5780 2.8 Initial Slip (Scale 1-5) Total End Feel (Scale 4-20) PEG 1540 PEG 600 Glyccryl Triglyceryl PEG 200 PPG 2000 PEG 400 di- Decaglyceryl octa- Decaglyceryl deca- Decaglyceryl tetra- Diglyceryl di- Isostearyl Isodecyl Oleyl Hexadecyl n-Decyl 1.3 PEG 1540 2.2 Triglyceryl 3.5 Glyceryl 3.7 PEG 600 4.0 PPG 2000 4.0 PEG 200 3.5 Decaglyceryl tetra- 4.0 Decaglyceryl octa- 4.0 Diglyceryl di- 4.3 Decaglyceryl deca- 4.8 PEG 400 di- 3.0 Hexadecyl 3.5 Isostearyl 4.0 n-Decyl 4.0 Isodecyl 4.5 Oleyl 73 77 83 87 11 3 15 7 8.5 9.3 11.3 11.5 14.5 13.0 15.0 17.0 17.0 18.5