EMOLLIENCY AND CHEMICAL STRUCTURE 643 all the polyol esters of oleic acid tested. Within this subgroup, there seems to be no correlation between End Feel and molecular weight, nor with per cent branching. The best End Feel was obtained from oleyl oleate, but we do not think that this richer skin feel is due to the addi- tional unsaturation. As a gToup, all these fatty alcohol esters of oleic acid gave rich Initial Feel and slip, as well as rich End Feel. For the ESTERS OF STEARIC ACID (Table IV), it should be noted that the End Feel score for PEG 1000 monostearate is less than half that of the fatty alcohol monostearates. The best End Feel score was obtained from butyl stearate, where stearic acid represents ahnost 83% of the molecule. Branching, in this series, did not seem to improve End Feel substantially. The poor performance of PEG 1000 monostearate may be due in some measure to the almost watery viscosity lotion which it pro- duced. Table IV Esters of Stearic Acid XXX 55% C,.6 acid--CH•(CH,•)•4COOH• Commercial 45% C•8 acid--CH.¾CH2)•.6COOH•Stearic (Mol Wt 270) Approx Carbons on Viscosity Mol Wt Alcohol (Lotion) (cps) Branching Butyl stearate Isodecy] stearate Hexadecyl stearate PEG 1000 monostearate Initial Slip (Scale 1-5) PEG 1000 3.0 Butyl 3.5 Hexa decyl 4.0 Isod½cyl 4.5 326 4 2144 ... 410 10 5230 3.7 494 16 2322 17.2 1247 44+ 39 ... End Feel (Scale 4-20) PEG 1000 6.5 Isodecyl 16.3 Hexadecyl 17.0 Butyl 17.0 Unfortunately, we were not able to obtain the same ESTERS OF 1SOSTEARIC ACID (Table V) as were available to us for stearic acid. Therefore, it is difficult to compare the two series. The only ester com- mon to both acids, that of isodecyl alcohol, shows the isostearic ester to be somewhat better, as would be expected. Note again that the two polyol esters gave substantially worse End Feels than the fatty alcohol esters in this series. ESTERS OF LINOLEIC ACID are shown in Table VI. Linoleic is another C•s acid, structurally identical to oleic acid except for an addi- tional double bond. Table VI shows that such extra unsaturation appears

644 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Esters of Isostearic Acid CHa CHaCH-(CH2)•4COOH = 73%• isoCi6 7%• Cørmnercial n-C•6/C•a 20%]Isostearic Acid (Mol Wt 280) Approx Carbons on Viscosity Mol Wt Alcohol (Lotion)(cps) Branching Isopropyl isostearate 327 3 5800 9.4 Glyceryl monoisostearate 336 3 2348 4.5 Isodecyl isostearate 420 10 2544 7.1 n-Decyl isostearate 420 10 2360 3.5 PEG 600 monoisostearate 862 26-4- 118 1.8 Initial Slip (Scale 1-5) End Feel (Scale 4-20) PEG 600 3.5 Glyceryl 11.1 n-Decyl 3.5 PEG 600 13.5 Glyceryl 4.3 n-Decyl 16.5 Isopropyl 4.5 Isopropyl 16.8 Isodecyl 5.0 Isodecyl 17.8 Table VI Esters of Linoleic Acid CHa(CH,,)4CH:CHCH2CH:CH(CH•)7COOH C•a Acid (Mol Wt 261) Approx Carbons on Mol Wt Alcohol Viscosity (Lotion)(cps) Branching Isopropyl linoleate Propylene glycol linoleate Decyl linoleate Hexadecyl linoleate PEG 400 linoleate PEG 4000 linoleate Initial Slip (Scale 1-5) Isopropyl 3.0 Decyl 3.0 Propylene glycol 3.5 PEG 4000 3.5 Hexadecyl 3.5 PEG 400 4.5 303 3 319 3 401 10 485 16 643 174- 4243 1804- 1144 4.9 5450 ... 7900 ... 9900 17.6 277 207 End Feel (Scale 4-20) PEG 4000 8.0 Propylene glycol 11.0 PEG 400 12.0 Hexadecyl 12.5 Isopropyl 13.0 Decyl 14.5 to reduce End Feel scores, and therefore usefulness as cosmetic emollients. On the other hand, since oleic acid esters performed better than stearic esters, a little unsaturation is apparently good.