Chemistry for Cosmetics Dr Lida Schoen Amsterdam Human skin Lida Schoen Chemistry of hair and skin products 2 ‘Dirt’ on the skin • water soluble (sweat); • oil soluble (sebum, grease); • non soluble (sand, skin flakes). Rubbing with water and soap can remove all three. Lida Schoen Chemistry of hair and skin products 3 Cleaning the skin: water and soap Lida Schoen Chemistry of hair and skin products 4 Washing dirt from textiles with water and soap Lida Schoen Chemistry of hair and skin products 5 ‘Cosmetic’ cleaners Showergel (=shampoo) Lida Schoen Chemistry of hair and skin products 6 ‘Cosmetic’ emulsion • • • • Water Oil Emulsifier Additions – Perfume – Colour Lida Schoen Chemistry of hair and skin products 7 Emulsion: micro Lida Schoen Chemistry of hair and skin products 8 Emulsion: macro Lida Schoen Chemistry of hair and skin products 9 Cream • 2-3% emulsifier + thickener (for stabilisation) • 10% oil like – mineral like paraffin (cheap, doesn’t deteriorate) – vegetable like avocado (what’s good to eat …), – animal like mink (snob appeal) • Water • Perfume • Additive, like – dihydroxyacetone (artificial tanning) – herbals Lida Schoen Chemistry of hair and skin products 10 Flowers, herbals Lida Schoen Chemistry of hair and skin products 11 Hair under microscope Lida Schoen Chemistry of hair and skin products 12 Chemistry: keratin • Hydrogen bridges • Ion-ion (salt) bonds • Disulfide (sulpher) bonds Lida Schoen Chemistry of hair and skin products 13 Keratin (2) Lida Schoen Chemistry of hair and skin products 14 Keratin (3) pH = 5,5 Lida Schoen Chemistry of hair and skin products 15 Keratin (4) cystin Lida Schoen Chemistry of hair and skin products 16 All bonds (schematic) Lida Schoen Chemistry of hair and skin products 17 Lida Schoen Chemistry of hair and skin products 18 Melanin in cortex Eumelanin • black-brown; • large molecules; • easy to light up. Pheomelanin • yellow-red; • smaller molecules; • difficult to light up. Lida Schoen Chemistry of hair and skin products 19 Lida Schoen Chemistry of hair and skin products 20 Hair colour Lida Schoen Chemistry of hair and skin products 21 Hair cleaning: shampoo Detergent: sodium lauryl (=C12) ether sulphate: • • • • cheap skin friendly good foam easy to thicken (with NaCl) Lida Schoen Chemistry of hair and skin products 22 Ether sulfates • Vegetable oil, after hydrolysation and reduction, ethoxylation with ethylene oxide • Alkyl alcohol esterified with sulphuric acid: CH3-(CH2)10-CH2(OCH2CH2)n)OSO3- Na+ with 1<n<4 Lida Schoen Chemistry of hair and skin products 23 Thickener: electrolyte • detergent in water: micelles • NaCl (3-4%) Lida Schoen Chemistry of hair and skin products 24 Conditioner in the past: egg yolk Egg shampoo: • Egg yolk: lecithin Conditioner today: man made •quat = quaternary ammonium compound •silicone Lida Schoen Chemistry of hair and skin products 25 Hair in form 1775 today Lida Schoen Chemistry of hair and skin products 26 Hair gel at school Carbomer (brand name in Europe): neutralised cross linked polymer of acrylic (propene) acid CH2=CH-COO-Na+ Lida Schoen Chemistry of hair and skin products 27 Bleaching (1) • Decomposition of melanin by oxidation in alkaline (ammonia) environment; • carboxylated derivatives soluble at higher pH’s. Lida Schoen Chemistry of hair and skin products 28 Bleaching (2) • Bleaching powder: persulphate: (O3S-O-O-SO3)22 Na2S2O8 -> 2 Na2S2O7 + O2 • Hydrogen peroxide, (max. 12%, pH = 4), optimum melanin bleaching at pH pKa (11,5) of the peroxide-anion. • In practice: pH = 10. H2O2(aq) 12% not stable at pH = 10. Lida Schoen Chemistry of hair and skin products 29 Types of hair colouring • Oxidative – permanent • Direct – semi-permanent – temporarily Lida Schoen Chemistry of hair and skin products 30 Hair colouring products • • • • • Natural Metal Permanent (synthetic dyes) Semi-permanent (natural en synthetic dyes) Temporarily (synthetic dyes) Lida Schoen Chemistry of hair and skin products 31 Lida Schoen Chemistry of hair and skin products 32 Lida Schoen Chemistry of hair and skin products 33 walnut henna Lida Schoen Chemistry of hair and skin products 34 Semi-permanent hair colouring • in and under cuticle • 4-6 washings • till 30% grey covering Lida Schoen Chemistry of hair and skin products 35 Metal ‘dyes’ • Acetates or sulphates of: lead, silver, iron, copper, cobalt, bismuth, manganese, zinc • Sulphide bonds with sulphur from keratin • Toxic properties! • Sensitive to oxidation Lida Schoen Chemistry of hair and skin products 36 Permanent hair colouring • Oxidative dyes: ‘development’ with hydrogen peroxide • Not washable • Till 100% grey covering Lida Schoen Chemistry of hair and skin products 37 Developers and couplers Ontwikkelaars = developers NH2 NH2 NH2 NH2 CH3 NH2 p-Fenyleendiamine CH3 NH2 OH Tolueen-2,5-diamine p-Aminofenol OH 4-Amino-m-cresol Koppelaars = couplers NH2 NH2 NH2 NH2 OH OH OH OH CH3 m-Fenyleendiamine Lida Schoen m-Aminofenol p-Amino-o-cresol Chemistry of hair and skin products Resorcinol 38 Examples of couplings Lida Schoen Chemistry of hair and skin products 39 Summary chemical ‘trick’ • Mix two (or more) kinds of small molecules; • cover hair with mixture; • small molecules intrude the hair cortex (higher pH will help to open cuticula); • inside the cortex small molecules react to much bigger molecules; • The big molecules are captured in the cortex, they can’t leave: permanent hair dye Lida Schoen Chemistry of hair and skin products 40 Bath salts 1. Salt 1. 2. 3. 4. kitchen salt: soda : bicarbonate: phosphate: NaCl Na2CO3 NaHCO3 Na3PO4 (cheap, crystals) (softener) (solubility) (complexer) 2. Perfume 3. Colour (water soluble food colour) 4. Extra (chamomile, herbals) Lida Schoen Chemistry of hair and skin products 41 Perfume (1) • Natural (past) and synthetic (aldehydes, ketones, esters) • Mixture of 3 groups ‘notes’: – Top; – Middle; – Base. Lida Schoen Chemistry of hair and skin products 42 TOP citrus green fruity lime, lemon , mandarin, orange, grass, apple, pineapple, cassis, raspberry, peach MIDDLE jasmin, rose, violet, muguet floral sandalwood, cedarwood, ambery, musky, vanilla, sweet hay BASE woody powdery Lida Schoen Chemistry of hair and skin products 43 ‘Our’ Chanel Allure • • • • • • citrus: 15 drops (top) lily of the valley: 8 drops (top/ middle) rose: 2 drops (middle) jasmin: 10 drops (middle) floral bouquet: 5 drops (middle) sensual: 10 drops (base) Lida Schoen Chemistry of hair and skin products 44 Dilution • With min 70% alcohol • Denaturated (tax reasons) with bergamot (citrus) or DEP (di-ethylphtalate) • Perfume: • Eau de Toilette: Lida Schoen 20% oils 5% oils Chemistry of hair and skin products 45 Allure – Fragrance Description From the Chanel website: • The concept of Allure was Coco Chanel’s ideal: an innocent seduction without artifice, an unforgettable elegance transcending words and conventions. • Fragrance family: floral, fresh, oriental. A faceted fragrance that mixes notes of the Orient with abstract flowers. • A simple jewel that combines 6 complex facets. In Allure, you’ll find bergamot, mandarin, water lily & magnolia, jasmine and may roses, vetiver and finally, the velvety sensuality of vanilla. Lida Schoen Chemistry of hair and skin products 46