Outline. Elements of Polymer Science. They are usually classified according to their use

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1 Polymers in Skin Care Cosmetics Outline 1. Introduction to 2. Polysaccharide Based Polymers in Cosmetics 3. Synthetic ti Polymers in Cosmetics Ampa Jimtaisong, PhD School of Cosmetic Science Mae Fah Luang University 2 Polymers are molecules consisting of a large number of identical low molar mass units, named repeat units, that are connected covalently. If A is the base unit, then a polymer molecule or macromolecule is represented by: A A A A A A or (A) n They are usually classified according to their use thickening agents film formers resinous powders humectants 3 4 Natural polymers, gums and resins Used in the industry since the early 1940s as water soluble binders, thickeners, and film forming agents. Today s products the growing consumer demand d for natural products. Drawbacks of natural polymers vary in purity & physical appearance relatively expensive (compared to common synthetic polymers) Problems of using natural polymers securing stable supplies variations in viscosity microbial contamination Synthetic or semi synthetic polymersdeveloped to match the properties of gums & resins

2 Natural Polymers or Biopolymers Proteins and Polypeptides Polysaccharides Synthetic Polymers 1. Biopolymers Proteins and Polypeptides. Proteins: the repeat units in proteins are amino acids. Amino acids in proteins are linked by an amide linkage between the amino group of one molecule and the carboxyl group of another. This amide bond is often called peptide bond Biopolymers Proteins and Polypeptides. Simple proteins composed only of amino acids >albumin, gelatin, casein, collagen, or keratin. Glycoproteins contain amino acid residues and carbohydrates Lipoproteins contain amino acid residues and lipids Proteins that possess catalytic activity > enzymes Biopolymers Polysaccharides. The repeat units of polysaccharides are simple carbohydrates (sugar units) linked to each other by acetal bonds. Among the important polysaccharides are homopolymers of glucose (starch, glycogen, and cellulose), amino sugars (chitosan and hyaluronan)

3 2. Synthetic Polymers Considering the application of polymers: (1) plastics (2) fibers (3) rubbers Definitions and Nomenclature Homopolymers are derived from one type of monomer. Copolymers require two or more species of monomers. Copolymers are distinguished according to the sequence of the various monomer units Definitions and Nomenclature Sequence of Monomer Units in Various Copolymers Copolymer type Random Alternating Diblock Triblock Graft Schematic composition Polysaccharide Based Polymers in Cosmetics 15 INTRODUCTION Outline POLYSACCHARIDE STRUCTURE POLYSACCHARIDES FUNCTIONALITY Cationic Polysaccharides Amphoteric Polysaccharides INTRODUCTION Polysaccharides perform a myriad of cosmetic functions: Rheology modifiers Suspending agents Hair conditioners Wound healing agents They moisturize, hydrate, emulsify, and emolliate

4 INTRODUCTION Does a polysaccharide that conditions do so at the expense of its thickening ability? How will it behave in the presence of surfactants or salts? Does it complex with other components of the formulation? POLYSACCHARIDE STRUCTURE Polysaccharides are sometimes referred to as polyglycans or hydrocolloids. Hydrocolloids for food use. Monomers= monosaccharides ( one sugar ) in polysaccharide chemistry Monosaccharides & Polysaccharides POLYSACCHARIDE STRUCTURE Monosaccharides & Polysaccharides Name R1 R2 R3 R4 R5 R6 R7 R8 D-Glucose H OH OH H H OH CH 2OH H D-Glucuronic acid H OH OH H H OH CO 2 H H D-Mannose OH H OH H H OH CH 2 OH H D-Mannuronic acid OH H OH H H OH CO 2 H H D-Galactose H OH OH H OH H CH 2 OH H D-Galacturonic acid H OH OH H OH H CO 2 H H L-Guluronic acid OH H OH H H OH H CO 2 H POLYSACCHARIDES FUNCTIONALITY Cationic Polysaccharides 1. Naturally Occurring 2. Seminatural

5 1. Naturally Occurring d. Xanthan Gum. Isolated from marine brown algae and from bacterial fermentation Comprised of two different monosaccharides: β D (1,4) mannuronic acid, 4 α L (1,4) guluronic acid, Partial structure of alginic acid showing β-d-(1,4)-mannuronic acid, 4, and α-l-(1,4)- guluronic acid, 5, residues. 27 Junction zones formed between alginic acid and Ca 2+ ions. sodium alginate, calcium alginate 28 Formulations that employ alginates must control polyvalent metal ion concentrations through the use of sequestrants such as ethylenediaminetetraacetic acid (EDTA), to optimize viscosifying effects of the alginate. Most of the anionic polysaccharides are affected to some degree by fluctuations in ph at the higher & lower extremes. Stable at ph

6 alginates are not stable at ph<3.0 owing to hydrolysis of the glycosidic bonds holding the polysaccharides together. unstable at high ph (above 10) 1. Naturally Occurring d. Xanthan Gum. Effect of ph on alginate solution viscosity Pectin is isolated by extraction from citrus fruit peels. Its structure is similar to that of alginic acid, except pectin is comprised of repeating α D (1,4) D galacturonic acid units (6), which are interrupted occasionally by an α L (1,2) rhamanose (7) Partial structure of pectin showing a-d-(1,4)- galacturonic acid, 6, and a-l-rhamanose,7. Partially nonionic Pectin is sold in grades designated by methyl ester level. Lower levels of ester groups make the pectin more anionic. Pectin behaves much like alginic acid when its methyl ester levels l are bl below 50%; it forms turbid gels in the presence of divalent metal ions, calcium in particular. At high methyl ester levels, it can form gels without divalent ion, but the concentration of polysaccharide required is typically much higher. Pectin is well suited for low ph applications considering its source (functions ideally at phs near 3.5) Below thisph, it suffersfrom from hydrolysis andin highlyalkaline solutions, hydrolysis of the ester is rapid

7 1. Naturally Occurring d. Xanthan Gum. The carrageenans are isolated from marine red algae. At least seven varieties of carrageenans are known, differentiated by Greek letters. The carrageenans of greatest tcommercial ilinterest tare primarily comprised of two repeating monosaccharides : β D (1,3) galactose (8) and α D (1,4) galactose (9). The most commercially accessible varieties include kappa (k), iota (i), and lambda (λ) carrageenan Carrageenan type R1 R2 R3 R4 R5 Kappa (strong, rigid gels) OH OSO - 3 O OH CH 2 Iota (soft gels) OH OSO 3 - O OSO 3 - CH 2 Lambda OSO 3 - OH OH OSO 3 - CH 2 OSO 3 - Anionic, highly acidic, hydrophilic Naturally Occurring d. Xanthan Gum. d. Xanthan Gum. Bacterial fermentation Show remarkable viscosity stability at increasing temperatures Stable at ph 1 12, Stable to heat Xanthan gum solutions are pseudoplastic. Xanthan gum is incompatible with most cationic surfactants. Xanthan s thickening efficiency is synergistically enhanced by the addition of colloidal magnesium aluminum silicate (Veegum)

8 Partial structure of xanthan gum showing β-d- (1,4)-glucose, 10, acetylated β-d-(1,2)- mannose, 11, β-d-(1,4)-glucuronic acid, 12, and pyruvic acid terminated β-d-mannose,13. d. Xanthan Gum. 1. Naturally Occurring d. Xanthan Gum Hyaluronic acid and chondroitin sulfate are isolated from various animal tissues. Cosmetic Hyaluronic acid is also commercially manufactured by bacterial lfermentation. ti Hyaluronic acid occur in the dermis of the skin being cellular turgidity (because of its water binding capacity) and lubrication. play a key role in wound healing. Hyaluronic acid and chondroitin sulfate are covalently bound with various proteins in the animal tissue proteoglycans. The unique acetylated amine containing monosaccharide classified these polysaccharides as glucosaminoglycans (amino containing sugars) Polysaccharide R1 R2 Hyaluronic acid H H Chondroitin-4-sulfate SO - 3 H Chondroitin-6-sulfate H SO Naturally Occurring d. Xanthan Gum. comprised of two repeating units: β-d-(1,4)-glucuronic acid (14) N-acetyl-β-d-(1,3)-glucosamine (15)

9 The exudates gums are isolated from the sap of specific trees and bushes that use each particular sap for protection, fluid transport, and energy storage. All of the gumexudates are nontoxicand are generally recognized as safe for use in cosmetics. Arabic gum (Acacia) relatively low molecular weight high levels solids without significant viscosity buildup. dissolves in water at > 50 wt% solids flowable. its maximum viscosifying effect near ph 6.0 the viscosity drops quickly ph becomes higher or lower. Multivalent cations reduce the viscosity of solutions of arabic gum, but the gum will not precipitate Gum karaya gum karaya swells in water and develops significant viscosity even at low concentration. stickiness accompanies the swelling denture adhesives. performs best at ph values between 7 and 9 the viscosity depends on the order of hydration and ph adjustment. if it is hydrated first then the solution ph raised, the viscosity is higher than if dried polysaccharide is added directly to an alkaline solution. Gum tragacanth shares many of the functional properties found in xanthan gum. At low concentrations it produces high solution viscosities. Tragacanth has high ph stability its viscosity thins as the temperature increases. Tragacanth strongly binds multivalent cations: including calcium, precipitate the polysaccharide from solution Naturally Occurring 2. Seminatural a. Cellulose Gum (Sodium Carboxymethylcellulose) b. Carboxymethylchitin hi i a. Cellulose Gum or Sodium Carboxymethylcellulose (CMC) CMC is a chemically altered derivative of cellulose. Cellulose is a naturally occurring, structural polysaccharide found in all plants. Cellulose is composed of one repeating monosaccharide, β d d (1,4) glucose (16)

10 Partial structure and synthesis of cellulose gum, 18, showing repeating b d (1,4) glucose, 16, in cellulose backbone. a. Cellulose Gum or Sodium Carboxymethylcellulose (CMC) ph >4.5, CMC is in the salt form water soluble. ph <4.5, CMC water insoluble. The insolubility appears first as an increase in viscosity and phase separation occurs. Eventually, as the CMC continues to phase separate, the solution becomes hazy and precipitation occurs. CMC also dissolves in and thickens glycerin solutions (small amount of H 2 O added) a. Cellulose Gum or Sodium Carboxymethylcellulose (CMC) CMC forms association complexes with strongly anionic surfactants addition of sodium dodecyl sulfate to a solution of dissolved CMC forms gels. Cationic surfactants have strong ionic interaction with CMCneutralize the charge of CMC At the point of charge neutralization, phase separation occurs. Stable at ph 4 10 Sensitive to heat, electrolytes 1. Naturally Occurring 2. Seminatural a. Cellulose Gum (Sodium Carboxymethylcellulose). b. Carboxymethylchitin b. Carboxymethylchitin. Carboxymethylchitin (CMCh), in Japan chitin liquid. It is manufactured by the carboxymethylation of chitin b. Carboxymethylchitin

11 POLYSACCHARIDES FUNCTIONALITY Cationic Polysaccharides Cationic Polysaccharides 1. Naturally Occurring Cationic Polysaccharides a. Chitosan. 2. Seminatural Cationic Polysaccharides a. Cationic i Hd Hydroxyethylcellulose thl lll Cationic HEC, 27, more commonly known by its INCI name, polyquaternium 10, is used as a conditioner delivered from shampoos & conditioners. The cationic HEC, 28 ( polyquaternium 4) is found as a conditioning & fixative adjuvant in hair fixatives. Chitosan Cationic Polysaccharides It is not cationic or water soluble unless the ph < 7.0 It is neutralized at these low ph values to the water soluble chitosonium salt (22). Commercially, the polysaccharide is often found neutralized with a cosmetically functional carboxylic acid such as lactic acid or glycolic acid, α hydroxy acids, Chitosan, employed as its salt, has strong substantivity to anionic surfaces like skin and hair chitin chitosan Chitosan salts Formation of chitosan, 21, and chitosan salts, 22, from native chitin,

12 Cationic Polysaccharides Chitosan It is a film forming polysaccharide that has been used in fixative formulations and 2 in 1 shampoos. Chitosan forms strong water insoluble associative complexes with most anionic surfactants. Evidence suggests that chitosan aids in the healing of wounds and damaged skin. ChitoGauze TM The Hemostatic HemCon Bandage 67 The chitosan bandage Battlefield Band Aids 68 POLYSACCHARIDES FUNCTIONALITY Cationic Polysaccharides 1. Naturally Occurring a. Starch. b. Cyclodextrins. 2. Seminatural lnonionic i Polysaccharides a. The Cellulose Ethers (5 sub types) b. Nitrocellulose a. Starch. amylopectin Starch is an energy storage polyglycan Corn, potato, rice, wheat, and tapioca It is composed of amylopectin and amylose Starch is an inexpensive, nontoxic polyglycan used primarily as a rheology modifier. The thickening effects of starch range from water thin viscosity to that of a gummy gel. amylose 71 The higher the ratio of amylose to amylopectin, the greater the thickening effect

13 b. Cyclodextrins Cyclodextrins are used extensively in cosmetic and drug delivery applications. The interior portion of the cyclodextrin is a lipophilic ( oilloving ) environment. If the lipophilic materials are water insoluble, their complex with a cyclodextrin may render them more water soluble. The exterior of the cyclodextrin is hydrophilic water soluble cyclodextrins. Cyclodextrin Naturally Occurring a. Starch. b. Cyclodextrins. 2. Seminatural lnonionic i Polysaccharides a. The Cellulose Ethers (5 sub types) b. Nitrocellulose a. The Cellulose Ethers The most popular and useful rheology control materials employed in the personal care industry. History of safe and effective use. The available cellulose ethers are generated from basic cellulose pulp and can be grouped, loosely, into a family tree. 75 (Handout) 76 a. The Cellulose Ethers Starting from cellulose, It can be treated with ethylene oxide to give hydroxyethylcellulose (HEC) propyleneoxide to give hydroxypropylcellulose (HPC) methyl chloride to give methylcellulose (MC) HEC can be treated with an activated ethylating agent to make ethylhydroxyethylcellulose (EHEC) HPC can be further treated with methyl chloride to afford hydroxypropylmethylcellulose (HPMC) Handout 77 a. The Cellulose Ethers Generally all of the cellulose ethers dissolve in water at room temperature and ambient pressure. Salts increase the solvent polarity, which reduces the solubilityofmore of lipophilic celluloseethersethers suchashpc and HPMC. Surfactants can increase the solubility or viscosity of slightly surface active cellulose ethers, such as HPC and HPMC. The effects, difficult to predict, are best evaluated experimentally

14 a. The Cellulose Ethers The solubility of most cellulose ethers decreases as their solution temperature increases. As the temperature continues to increase, finally the polysaccharide collapses upon itself and precipitates from solution. The temperature at which a cellulose ether falls out of solution is characteristic of that ether and is known as the cloud point (cp) a. The Cellulose Ethers i. Hydroxyethylcellulose. ii. Hydroxypropylcellulose iii. Methylcellulose iv. Hydroxypropylmethylcellulose v. Ethylhydroxyethylcellulose i. Hydroxyethylcellulose (HEC). HEC is unique among the cellulose ethers for its lack of a cp HEC is the most hydrophilic and most widely used cellulose ether. It is not soluble in many cosmetically practical organic solvents including the hydroalcoholic solvents. HEC is more tolerant to extremes of ph, salts, and surfactants than the other cellulose ethers. ii. Hydroxypropylcellulose (HPC) HPC has its cp at about 45 C. Above this temperature, it will not hydrate when added to water; if already dissolved, it will fall out of solution upon heating to 45 C. Hydration of the polysaccharide is best done by adding it to hot water, where it fully disperses, and upon cooling completely dissolves without clumping ii. Hydroxypropylcellulose (HPC) Because of the pendent methyl groups on the propylene oxide side chains, HPC is much more lipophilic than HEC. This allows HPC to dissolve in and thicken many organic systems such as ethyl alcohol, aqueous ethyl alcohol, and propylene glycol. HPC is tolerant to fluctuation of ph Surfactant and salts have influence on aqueous HPC iii. Methylcellulose (MC) MC has a gel point near 45 C. Above 56 C MC precipitates as a hazy cloud. MC shares many of the same solution attributes of HPC s chemistry, but tends to be more lipophilic than HPC. This enables it to dissolve and thicken a broader range of nonaqueous solvents including ethylene and propylene glycol, glycerin, and some oils

15 iv. Hydroxypropylmethylcellulose (HPMC) Hydroxypropylmethylcellulose shares characteristic solution properties of both HPC and MC. Because of its inherent lipophilicity and surface activity HPMC maintains stable oil in water emulsions even after heat sterilization. This provides unique opportunities to prepare sterile creams and lotions for pharmaceutical and dermatological applications. 1. Naturally Occurring a. Starch. b. Maltodextrins/Cyclodextrins. 2. Seminatural lnonionic i Polysaccharides a. The Cellulose Ethers (5 sub types) b. Nitrocellulose b. Nitrocellulose Nitrocellulose is one of the oldest known modified cellulose derivatives. It is manufactured by treating cellulose pulp with a combination of nitric and sulfuric acids. Levels of commercial nitration are extremely critical because cellulose, nitrated to levels greater than 12% nitrogen an explosive. Protein Based Polymers I. Animal Sources a) Collagen b) Elastin c) Keratin d) Milk Protein e) Silk Protein derivatives II. Vegetable Sources a) Wheat Gluten b) Soy Protein c) Corn (Protein Isolate) d) Casein e) Yeast Protein Thickening Polymers Outline Synthetic Polymers in Cosmetics Carbomers Polyvinyl pyrrolidone Polyvinylpyrrolidone vinyl acetate 90 15

16 Carbomer Synthetic Polymers Known as Carbopols, carboxypolymethylene, carboxyvinyl polymer or acrylic acid polymer It dispersed in water to form an acidic colloidal solution of low viscosity, which produces a high viscous gel on neutralization with inorganic or organic bases like sodium hydroxide, triethanolamine, etc. Carbomer Synthetic Polymers Carbomer gels are most viscous between ph 6 and 11. The viscosity is reduced on lowering the ph to below 3 or rising above 12. Electrolytes also reduce the viscosity of carbopol dispersions. Carbomer is susceptible to oxidation especially on exposure to light and hence formulations should be stabilized by addition of appropriate antioxidants and chelating agents Carbomer Synthetic Polymers Several viscosity grades are available and the usual concentration used varies from 0.1% to 4% as suspending agent. Carbomer 934 Carbomer 940 Carbomer 941 Synthetic Polymers Polyvinylpyrrolidone (PVP) It can dissolve in water and a variety of organic solvent. It has good hygroscopicity, film forming capability, complexing ability and physiology compatibility Synthetic Polymers Polyvinylpyrrolidone (PVP) Cosmetics: PVP K series can be used as filmforming agent, viscosity enhancement agent, lubricator and adhesive. PVP K30, PVP K85, PVP K90 They are the key component of hair sprays, mousse, gels and lotions & solution, hair dying reagent and shampoo in hair care products. Synthetic Polymers Polyvinylpyrrolidone vinyl acetate copolymer (PVP/VA) PVP/VA forms hard, glossy, water removable films. Itsviscosity viscosity, softening point and water sensitivity vary with PVP/VA ratio

17 Reference E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care (Cosmetic science and technology : v. 22), MARCEL DEKKER, INC, New York, NY, USA