Performance-Driven: New Silicone Copolymers

1 Performance-Driven: New Silicone Copolymers It is hard to recall when siliconeswere not considered key in-gredients for personal careproducts. In general, siliconesare utilized in many new for-mulations on the market, allowingfor flexibility and creativity by theformulator. Silicones can aid in thedifferentiation of products by influ-encing desirable aesthetic or func-tional silicones have had a long-use history,1-4 Dimethicone Copoly-ols, recognized as safe,5have notseen as wide an application profileas had been envisioned by the man-ufacturers of these raw a number of marketedformulations have used DimethiconeCopolyols and their use has beenwidely proposed and discussed,6-12formulators have often turned tolinear fluids to achieve perceivableeffects in Dimethicone Copolyols areinteresting polymers, from a struc-tural point-of-view, they often failto perform as expected in surfac-tant systems.

2 Dimethicone Copoly-ols as a group can be soluble inethanol, stearyl alcohol, and water;as a result, they can have applica-Experimenting with Dimethicone Copolyols for personal care products. By David T. Floyd & Holger I. LeidreiterDavid T. Floyd completed his undergraduate stud-ies in biology at the University of Lowell. He com-pleted his graduate studies in chemistry at BostonState College and in biochemistry at the Universi-ty of Massachusetts. He is a member of the Amer-ican Institute of Chemistry, the American Oil ChemistSociety, the Association of Formulating Chemists,and the Society of Cosmetic Chemists, with morethan 30 years experience in the cosmetic has a number of patents and publications in thearea of household, cosmetic, and pharmaceuticalformulations. He is also a lecturer for the Society ofCosmetic Chemists. Presently, Floyd is technicaldirector of the personal - care applications lab atGoldschmidt Chemical.

3 Holger I. Leidreiter, ,is manager for the personal -wash applications labat Goldschmidt-Germany. Dr. Leidreiter is widleyrecognized for his knowledge of the applications ofsurfactants and performance ingredients in per-sonal-wash. He has had several articles publishedand is also a lecturer at various chemical preferences: Determining foam quality and rinseability of formulations tested, Goldschmidt. New Silicone Copolymers tions in non-durable skin- care formulations where theycould provide the necessary Silicone properties, andthen wash off. They can serve as lubricants in non-durable skin creams and lotions, as wetting agents inaerosol shaving lather, and as emollients in liquid con-ditioning soaps. Because of their solubility, many Dime-thicone Copolyols could be useful in shampooformulations requiring using levels ranging from to weight per-cent, Dimethicone Copolyols are sufficient in providinglubricating and wetting characteristics to skin levels from to percent improves (decreas-es) wetting time and adds lubrication and foam stabilityproperties to shaving products.

4 In hair styling mousses,levels ranging from to percent make productsspread easily and reduce resin tack. Addition of a siliconeglycol can lower the surface tension of a water-basedmousse to 28 dynes/cm, the critical surface tension need-ed to wet virgin ,14 These silicones have also founduse in ethnic hair- care products, where they add non-greasy lubricating and softening qualities, act as humec-tants, and help reduce skin preparations, Dimethicone Copolyols canenhance water-repellency and improve retention of humid-ity, due to strong interaction between the polyethyleneglycol units and water. This is done without an adverse influ-ence on the natural skin pure dimethicones, Dimethicone Copolyols aretasteless, oxidation-resistant, and have a low odor. Theseproperties and their unique behavior as surfactants makeDimethicone Copolyols a very versatile and valuablegroup of personal - care Copoly-ols are recognized as safe-for-use in cosmetics and, infact, studies show their inclusion in anionic surfactant-basedproducts can reduce both eye- and ,3,15 The essential feature of dimethicone copolymer sur-factants, compared to purely organic surfactants, is themuch higher surface activity provided to the dime-thicone moiety.

5 For this reason, dimethicone copoly-mers are more effective surface tension depressants andprovide superior wetting and lubricating propertiesthan hydrocarbon-based organic outstanding surface activity of dimethicone copoly-mers is realized both in aqueous and organic on overall polydimethylsiloxane/polyoxyalkylenerati o and on the polyethylene glycol/polypropylene gly-col ratio in the polyether chains, the solubility behaviorof dimethicone Copolymers in water, alcohol, and otherorganic solvents can be varied over a wide range. Start-ing with a certain polydimethylsiloxane moiety, water-soluble Copolymers , which are insoluble in mineral oil,are obtained by linking them to polyethers, predominantlycomposed of polyethylene glycol. On the other hand, Copolymers , which contain polyethers consisting mainlyof polypropylene glycol, are easily soluble in oils but lesssoluble in ,11,16 The base structure of DimethiconeCopolyol is shown in Figure was quickly observed that while copolyols have verygood surfactant qualities with corresponding cosmeticqualities, the laboratory s observable effects are often over-looked by consumers.

6 What seemed to be lacking was a goodexpression of the Silicone nature of the molecule. Experi-ments were made to lengthen the siloxane backbone, butled to problems with viscosity and general incorporationinto a cosmetic vehicle. The typical backbone length usedin Dimethicone Copolyols, when related directly to linearsiloxanes, show good surface effects on skin and hair. Itwas speculated that traditional pendant structures used toplace the polyethers on the backbone may be masking thesilicone nature of the siloxane to siloxane bonds in the backbone ofsilicone are quite flexible and allow for rotation. (SeeFigure 2.)The polyethers, since they are chains of repeatingmonomers, can also wrap around the siloxane back-bone. Both of these motions could serve to mask the sil-icone nature of a has had previous successes with an , Silicone quaternary (Quaternium-80).

7 This quaternary,17,18in addition to a strong anti-static effect, also has a strongsilicone ,20,21 The , structure is an end organo-modification to a siloxane chain. (See Figure 3.)Figure 1 Polyether Polysiloxane CopolymerINCI (CTFA): Dimethicone Copolyol: PE = ( C2H4O)x( C3H6OH)y HCH3CH3CH3CH3 H3C Si O Si O Si O Si CH3 CH3(CH2)3CH3 n CH3 O PE m Figure 2 Rotation PotentialCH3CH3CH3 SiO SiO S i O RCH3 RRotation Potential of Pendant Groups on SiloxanePolyetherPolyetherA chain length similar to that of the Silicone quater-nary was selected after several trials varying the siloxanebackbone. A polyether was selected with a moderateEO/PO length with a ratio of polyethylene glycol topolypropylene glycol of 40:60. The polyether used wasbased on several experiments that looked at surfactantsurface tension reductions in sodium lauryl sulfate, thusgiving the resultant polymer a good water dispersabilitythat could be clearly solubilized in water with a mini-mum amount of the surfactant.

8 (See Figure 4.) To eval-uate the effects of the polymer on both hair and skin,in-vitro testing was copolyol was examined for its foam effects. Asimple sodium lauryl sulfate/sodium laureth sulfate basewas examined for the effects on flash foam, foam height,foam longevity, and foam density (weight). The foamwas also evaluated for visual appearance. In all cases, theinclusion of the copolyol showed improvements in thefoam generated. Figure 5 shows the effect on foam gen-erated through a foam valve when the copolyol is includ-ed in the surfactant simple hand-wash was developed. (See Table 1.) Twen-ty panelists were asked to alternate hand washing betweenthe test and control bases. Panelists were not madeaware of which formula was the test were asked to comment on foam qualityand rinseability of products tested. They assessed thefeel of the products during use, and after rinsing anddrying the hands.

9 Panelist preferences are noted inTable 1 Formulations TestedIngredients Control Test Water Tetrasodium EDTA Ammonium Laureth Sulfate Ammonium Lauryl Sulfate Cocamidopropyl Betaine PEG-18 Glyceryl Oleate/Cocoate Experimental Copolyol Ammonium Chloride % Total Table 2 Hand-Wash PreferencesControl Test None Better Foam 2 15 3 Smooth/Silky/Soft 4 13 3 Clean Rinse 4 6 10 Conditioning 3 13 4 Figure 3 , StructureR = Organic ModificationCH3 R S i O R CH3n Figure 4 Experimental Copolyol StructurePE = ( C2H4O)x( C3H6O)y Hx : y = 40 : 60 by weightCH3 PE SiO PE CH3 Figure 5 Foam ComparisonSeveral panel evaluations were made to further explorethe copolyol s addedControlNew Silicone Copolymers Hair-CareHair evaluations wereconducted first on tress-es and then on a sham-poo panel to correlateobservations.

10 For thesestudies, a simple sham-poo base was developed.(See Table 3.)The formulations werediluted to one part in 20in de-ionized in triplicate wereimmersed in the solutionsfor 15 minutes underslight agitation. Thetresses were removed,rinsed, and hung for a wetevaluation. Following thewet evaluation, the tress-es were oven-dried at40 C in an air circulationoven for three hours andre-evaluated. A total of20 individuals evaluated the tresses. The results arepresented in Table shampoo bases were given to 20 panelists. Thepanel was split with half receiving the control formu-lations, and the other half receiving the test formula-tions. The panel was reversed to correct for bias and theproducts re-evaluated. All panelists shampooed witheach formula three times. Each panelist was instruct-ed to daily shampoo their hair as they normally wouldand at the end of the shampooing, record their trying both formulations, panelists were asked toselect preferences for the formulations evaluated.