EMOLLIENCY AND CHEMICAl. STRUCTURE 645 Table VII Hexadecyl Alcohol and Esters o Cs/•CHCH20--CR Approx Carbons on Viscosity % Mol Wt Fatty Acid (Lotion)(cps) Branching Hexadecyl alcohol 242 0 790 35.1 Hexadecyl laurate 424 12 7100 20.1 Hexadecyl myristate 437 14 7150 19.5 Hexadecyl linoleate 485 18 5130 17.6 Hexadecyl oleate 500 18 5300 17.0 Hexadecyl stearate 508 18 2322 16.7 Initial Slip (Scale 1-5) End Feel (Scale 4-20) Laurate 3.0 Laurate 10.0 Alcohol 3.3 Linoleate 12.5 Linoleate 3.5 Oleate 13.0 Oleate 4.0 Alcohol 17.0 Stearate 4.0 Stearate 17.0 Myristate 4.3 Myristate 17.3 HEXADECYL ALCOHOL itself gives excellent End Feel, even though it produced a relatively low viscosity lotion (Table VII). Esteri- lying with oleic or linoleic acids substantially decreases performance. Esterifying with stearic or myristic acids does not affect End Feel at all, but does increase Initial Slip slightly. Esterifying with lauric acid de- creases performance. Unsaturation tended to decrease performance in this series. Three liquid (isoalcohol) ESTERS OF MYRISTIC ACID were avail- able for test, as well as one waxy one, myristyl myristate (Table VIII). On the whole, they all performed well. As expected, the three liquid isoesters gave somewhat better results than the solid normal ester. LAURIC ACID ESTERS seem to be poor emollients (Table IX). ESTERS OF ADIPIC ACID show extraordinarily good skin feel (Ta- ble X). All of these are diesters, since adipic acid is a dicarboxy acid the percentage of fatty alcohol or polyol in the molecule is therefore substan- tially higher than in monoesters. Results were so uniform in this series that it was difficult to draw any conclusions on the effect of systematically varying the structure of adipates. ESTERS OF LACTIC ACID also show uniformly excellent results, except for stearyl lactate, which performed poorly (Table XI). Isostearyl lactate shows an End Feel score of 17.5, 50% higher than that of the

646 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VIII Esters of Myristic Acid CHa(CH2)•2COOH C•4 Acid (Mol Wt 228) Approx Carbons on Viscosity Mol Wt Fatty Alcohol (Lotion)(cps) Branching Isopropyl Myristyl Hexadecyl Isostearyl Initial Slip (Scale 1-5) Myristyl 3.5 Isostearyl 4.0 Isopropyl 4.3 Hexadecyl 4.3 271 3 2276 5.6 448 14 24,700 ... 437 16 7150 19.5 479 18 7350 3.2 End Feel (Scale 4-20) Myristyl 16.3 Isopropyl 17.0 Hexadecyl 17.3 Isostearyl 18.3 Table IX Esters of Lauric Acid CHa(CH2)•0COOH C•a Acid (Mol Wt 200) Approx Carbons on Viscosity Mol Wt Alcohol (Lotion) (cps) Decyl laurate Hexadecyl laurate PEG 200 dilaurate PEG 400 monolaurate Initial Slip (Scale 1-5) PEG 400 monolaurate 2.0 PEG 200 dilaurate 3.0 Hexadecyl laurate 3.0 Decyl laurate 4.3 340 10 424 16 565 84- 582 17q- % Branching 6060 ... 7100 20.1 2208 ... 217 ... End Feel (Scale 4-20) Hexadecyl laurate 10.0 PEG 400 laurate 10.5 PEG 200 dilaurate 14.0 Decyl laurate 15.0 stearyl lactate (11.8). Although their molecular weights are theoretically identical, the two esters we tested differed slightly (as determined from actual saponification values), presumably due to different sources of raw materials. Oleyl lactate, also a C•s ester, gave an even higher End Feel score than isostearyl lactate. The two solid lactate esters gave only fair results, while all of the liquid lactates were excellent. A group of SATURATED FATTY ALCOHOLS was examined (Ta- ble XII). Here again, the pattern was similar: liquid alcohols gave better results than the solid ones. Furthermore, of the three liquid fatty alcohols evaluated, the two iso liquid fatty alcohols gave substantially