Pharmaceutical sciences
Cosmetics
Applications of polymers in cosmetics
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Development Team
Principal Investigator
Dr. Vijaya Khader
Former Dean, Acharya N G Ranga Agricultural University Prof. Farhan J Ahmad
Jamia Hamdard, New Delhi
Paper Coordinator Dr. Javed Ali
Jamia Hamdard, New Delhi
Content Writer Dr. Javed Ali
Jamia Hamdard, New Delhi
Content Reviewer Prof. (Dr.) R. N. Gupta
BIT, MESRA
Pharmaceutical sciences
Cosmetics
Applications of polymers in cosmetics
0
CONTENTS
Application of polymer/surfactant interaction
Application of synthetic polymers in cosmetics
Silicones in cosmetics
Polysaccharides based polymers in cosmetics
Proteins in cosmetics
Lather enhancer cellulosics in personal care products
Application of polymers in hair care
Applications of acetylene derived polymers for personal care
Methods of evaluation for conditioned hair
Organo-modified silicone copolymers for cosmetic use
Cosmetic use of chitin and chitosan
Cationic polysaccharides for cosmetics application
Assessment of polycation adsorption
Alkylated polyvinylpyrrolidone polymers in cosmetics
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Applications of polymer in Cosmetics
Cosmetics are defined by the FDA as “articles intended to be applied to the human body or any part thereof for beautifying, cleansing, promoting attractiveness, or altering the appearance”.
All the cosmetics products contain different types of polymers in their formulation according to their intended functions. Polymers are the second largest ingredient in cosmetics and personal care products. A widest range of polymers are used in the cosmetics like rheological modifier, emulsifier, stimuli- responsive reagents, conditioners, film formers, fixatives, foam stabilizers and destabilizers, skin-feel beneficial agents and antimicrobials.
Polymers in the cosmetic industry are categorized on the basis of different classifications in the International Nomenclature Cosmetics Ingredients (INCI) dictionary, including organic polymers, inorganic polymers, siloxane polymer and naturally occurring polymers. These classifications are further divided into subclasses: homo polymer, co-polymer, cross linked polymer, mixed classification polymers, dendrimers, natural sourced polymer, synthetic peptides.
Polymer/Surfactant interaction
According to the royal society of chemistry the surfactants are used in all products for skin cleansing.They break up the oily component produced by the skin, which is easily washed by water. The surfactants arealso used as a spreading agents, emulsifier, etc. The surfactants are classified according to the charges present on its hydrophilic group.
A. Amphoterics
Surfactants are classified as amphoteric surfactant only if charges on its hydrophilic head changes as a function of pH. Hydrophilic head carries positive charges at low pH and negatives charges at high pH and form internally neutralized ionic species (zwitterions) at an intermediate pH. Amphoteric surfactant having hydrophilic head and hydrophobic tail is shown below in figure 1.ex.alkylamido alkyl amines and alkyl substituted amino acids.
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.
Figure 1: Amphoteric surfactant .
B. Anionics
Surfactant in which negative charges present on hydrophilic head is classified as anionic surfactant as shown below in figure 2.
Figure 2: Showing Anionic surfactant
Anionic surfactant is further classified into five major classes and subgroups- 1. Acylated amino acids and acyl peptides.
2. Carboxylic acids and salts- carboxylic acid anionic surfactant like stearic acids are used to prepare stick products like deodorants, lipsticks, antiperspirants.
Alkanoic acids
Ester- functional carboxylic acids
Ether- functional carboxylic acids 3. Sulfonic acid derivatives
Taurates
Isethionates
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Alkyllarylsulfonates
Olefin Sulfonates
Sulfosuccinates
Miscellaneous Sulfonates 4. Sulfuric acid derivatives
Alkyl sulfates
Alkyl ether sulfates
5. Phosphoric acid derivatives.
The member of these five classes form water soluble salts with alkali metals and low molecular weight amines (alkanol amines).
C. Cationics
The cationic surfactants carry positively charged nitrogen atom on the hydrophobe. Cation surfactant having positive charge on head is shown below in figure 3.
Figure 3: Cationic Surfactant
The positive charge may be independent of pH in quaternaries or may be pH dependent in amines. They are subdivided into-
1. Quaternaries
(a) Alkyl benzyl dimethylammonium salts (b) Alkyl betaines
(c) Tetraalkylammonium salts (d) Heterocyclic ammonium salts 2. Alkyl amines
3. Alkyl imidazolines.
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D. Nonionics
These are the surfactant in which the molecules carry no charge at the pH levels of cosmetic use.
The non-ionic surfactant having hydrophilic head and hydrophobic tail is shown below in figure 4.
Figure 4: Nonionic Surfactant
Nonionics are further divided into 5 major groups.
1. Alcohols – ethoxylated linear alcohols, ethoxylated alkyl phenols 2. Esters - fatty acids esters
3. Ethers - Ethleneoxide
4. Alkanolamides - alkylpolyglucosides 5. Amines Oxides – thiols (mercaptons)
The potential complexity of surfactant interactions in solution known as “spectrum” which is depicted in figure 5, where S, L, V refer to solid, liquid and vapour phases respectively. This figure 5 shows the adsorption of surfactant at liquid vapour interface which leads to the formation of monomer solution which will be further converted into crystalline form, bilayer vesicle, micelle or liquid crystals. This monomer solution can also be adsorped at solid liquid intersurface or at liquid liquidintersurface.
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Adsorption at L/V interface
Monomer solution
Figure 5: Surfactant/polymer interaction at the interface of liquid vapour interface.
The forces that control the surfactant interaction with polymers are fundamentally same as involved in other solution or interfacial phenomena namely Vander Waals or dispersion forces, hydrophilic effects, dipolar or acid-base interactions and electrostatic interaction.
The factors affecting the interaction between surfactant and polymers are almost similar to the factors that affect micellization of surfactants which are mentioned below-
1. Surfactant chain length
For uncharged polymer the binding concentration in homologous series of ionic surfactant decreases with increasing chain length of the surfactant.
2. Surfactant structure
In this, the nature of head group in the surfactant is the most noticeable factor in the interaction with simple uncharged water soluble polymer. Non-ionic surfactants are unreactive towards simple uncharged polymer. The anionic surfactants are very strongly reactive towards polycation polymer but very weekly or non-reactive towards anionic polymers.
3. Polymer characteristic
(a) Weight of polymer- Several ranges of minimum weight of polymer require for the interaction of surfactant with polymer. The hydrophobically modified polymer weight of Crystalline
e
Bilayer &
Vesicle formation
Adsorption at S/L intersurface e
Adsorption at L/L intersurface
Liquid crystals Micelle formation
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1000 shows ready interaction not only with cationic and anionic surfactant but also with non-ionic surfactants.
(b) Amount of polymer- The amount of polymers and surfactants must be same for the interaction between two.
4. Polymer structure
For the interaction between ionic surfactant and uncharged polymers, there must be definitive difference in reaction affinity among polymers and given surfactants.
5. Added salts
Addition of salts effect the interaction between ionic surfactants with polymers where aggregation of surfactant is also possible. The effects can be quite complex and may vary from system to system, with pH, with the absolute ionic strength and with other variables.
Application of Synthetic polymers in Cosmetics
The application of synthetic polymers has been tremendously increasing in the cosmetic industry. Nowadays, the petroleum based polymers are being widely used in personal care products. The synthetic polymers are classified into two types – condensation polymer and addition polymer. In many laboratories water soluble synthetic polymers like poly (vinyl pyrrolidone), poly (vinyl alcohol), poly (ethylene glycol), poly (ethylene oxide) are blended with natural polymers like collagen, elastin, keratin, silk and gelatin to form a thin films, hydrogels used in cosmetics, sponges.
The most important use of synthetic polymers are as a thickening agent by different mechanism of actions.
1. Thickening by chain Entanglement
The most straight forward mechanism of thickening is by chain entanglement. Solution viscosity increases with increase in the concentration of polymer in the formulation as the more and more chains occupy a limited space. Increase in molecular weight also plays a very important role in chain entanglement.
The chemical identity significantly affect the behaviour of polymers like copolymer or crosslinked polymer or hydrophobically modified polymer. For instance, polymers with different viscosity behave differently in the formulation as the simple linear polymers
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(poly[(metha)acrylic acid], poly (ethylene oxide), poly (vinyl alcohol and poly(vinylpyrrolidone)) influence solution viscosity through random chain entanglement.
2. Thickening by covalent Cross-linking
The covalently cross-linking polymer include hooking two polymers chain together byinsertion of a bifunctional monomer that can react with both the chains radically. Such cross linking aqueous solution polymers increases the usefulness of that polymer to some extent.
3. Thickening by an Associative Mechanism
The associative thickening polymer are those polymers that have been hydrophobically modified to provide them surfactant like qualities. The associative aggregation in a solution affect the viscosity of solution, spreading behaviour, film thickness and feel of cosmetics (from lotions to gels to shampoos). Along with the thickening affect, the synthetic polymers are used as fixative polymers which have been applied to the hair as liquids, gels and foams.
Silicones in cosmetics
Over the last 50 years, the silicone materials in hair care and skin care products have been used in cosmetic industry. The incorporation of silicone in skin care products is quite early as compared to hair care formulation. Revlon was the first to launch silicon containing skin care lotion named as Silicare skin lotion. The increased use of silicones in cosmetics is only possible by the development of new technology in the areas of emulsification, associative thickeners, and suspending agents. The organofunctional silicones have additional advantage of providing multifunctional benefits to the formulations. The silicones and its derivatives are widely used in cosmetics such as in deodorant stick, shampoos, antiperspirant, lotion, etc.
Figure 6 : Structure of Dimethicone and Cyclomethicone
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Silicones are derived from natural product known as Silica (basic sand) and after various chemical modification it is used in personal care products. Dimethicone and Cyclomethicone are the two modified silicones used in cosmetics for water proofing, retaining moisture, adhering colour pigments, protecting hair and imparting smoothness and providing silkiness to hair. They are used in deodorants to provide velvety feel, in sunscreen cream as a water resistant, lubricating and massaging agent, in anti-aging and in anti-wrinkle creams.
Dimethicone and dimethiconol are the types of silicones spread uniformly into thin films over the surface of hair and skin to provide hydrophobicity to the surface of skin and hair. They add lubricity, shine and humidity resistance to hair in addition to providing breathable, protective barrier to skin. For increasing the durability of these film over the skin and hair, high molecular weight dimethicone gums or silicone resins such as trimethylsiloxysilicate can be added into formulations.
Alkyl Modified Silicone (AMS) are used in skin care, sun care and other cosmetics products to form an occlusive barrier on the skin. This material is an excellent moisturizing agent, reducing transepidermal water loss (TWEL) to a level comparable to petrolatum. In lipsticks formulation, it is widely used as a stick integrity agent, impart an occlusive barrier, provide moisturizing effect to the lips, enhance pigment release and reduce pigment transfer from other ingredient present in the formulations.
Polysaccharides based polymers in cosmetics
Polysaccharides play very important role in cosmetic formulation technology along with other ingredients such as surfactants, salts and other polymers. Cosmeceuticals are widely used as skin cleansers, moisturizer and sunscreen as well. Now a day, new class of products has been gaining popularity in skin care regimens as adjuvant against inflammatory disorders and skin aging.
Galacturonans is the main polysaccharides of hydrolysedmyrtuscommunisextract,.Itforms gels in the presence of water. The deposition of this gel over the skin provide tightening to the skin and function as antiaging formulation.
Alginic acid is a linear polysaccharides made up of lucoronic and mannuronic acids as a thickening agents in various formulation such as toothpaste, soap, shaving cream and hair gels.
Agar- agar or gelose and carragenates are also natural polymer produced from plant used as thickening and emollients agents in creams, suspensions, toothpaste, etc.
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Polysaccharides can be natural and synthetic and further classified into anionic, cationic, non- ionic and even amphoteric depending upon chemical identity expressed on its backbones. Starch is also a polysaccharides containing numbers of glucose unit as a monomer shown in figure 7.
Figure 7: Structure of polysaccharides.
(a) Anionic polysaccharides
The two most commercially available polysaccharides named as cellulose gum and carboxymethylchitin were made anionic by manual intervention using carboxymethylation of naturally occurring cellulose and chitin respectively. Carboxymethylcellulose increase the viscosity of cosmetic formulation through entanglement of its high molecular weight chains.
Structure of anionic polysaccharides shown below in figure 8.The naturally occurring other anionic polysaccharides are alginic acid, carrageenans, xantham gum, hyaluronic acid, chondroitin sulfate and gum exudates like arabic, karaya, and tragacanth.
Figure 8: structure of anionic polysaccharides.
(b) Cationic polysaccharides
Synthetically altered polyglycans can be used as cationic polysaccharides in cosmetics. Cationic Polysaccharides are widely used in hair conditioners to control the hair damage. Chitosan is not
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cationic and water soluble unless the pH value is below 7. The polysaccharides are generally found neutralized with cosmetically functional carboxylic acid such as lactic acid or glycolic acid, a component of the natural moisturizing factor found in skin. Structure of cationic polysaccharides shown in figure 9.
Figure 9: Structure of Cationic polysaccharides.
Only three cationic polyglycans are commercially used in cosmetics- cationic hydroxyethylcellulose, cationic guar and cationic hydroxypropylguar.
(c) Non-ionic polysaccharides
These polysaccharides do not carry any formal charge. Rheology modifier and thickeners are the two main uses of these polysaccharides in cosmetics. The viscosity is related to the ratio of amylose to amylopectin in particular polysaccharides used in cosmetic formulation. Structure of non-ionic polysaccharide shown in figure 10. The higher the ratio of amylose to amylopectin, the greater is the thickening effect to formulations. Ether modified cellulose and guar based materials as seminatural non-ionic polysaccharides are extensively used in cosmetics.
Figure 10: Structure of Non-ionic polysaccharide
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(d) Amphoteric Polysaccharides
These are those polysaccharides which carrying both cationic and anionic charges on same chain.
Generally, seminatural derivatives are used in cosmetics as very few are available naturally.
Figure 11: Structure of Amphoteric Polysaccharides.
The use of amphoteric polysachharides is very challenging as it contains both the charges and insoluble in zwitterionic form. Carboxymethylchitosan and modified potato starch fall under this category. Hydrophobically modified polysaccharides and polysaccharides with topical physiological effects are the two other types of polysaccharides usually used in preparation of cosmetics.
Proteins in Cosmetics
From the ancient time the protein has been widely used in cosmetics. Protein is considered as useful ingredient in cosmetic as it establishes suitable environment for skin and hair to retain water. Milk was the first proteinaceous ingredient used in cosmetics. Milk protein is usually composed of casein and acidic phosphoprotein form colloidal dispersion. Silk powder and sericinhydrolysates are used in cosmetics. The largest part of the body is the skin made up of 25% protein. The practical use of protein substances includes use of camel milk to clean skin and hair. Furthermore, donkey milk and soy flour are used to prepare facial masks.
Hydrophobicity of protein is the critical parameter of cosmetics efficacy. The hydrophobicity of peptides affects the cosmetic property of protein like substantivity to hair and skin, the binding capacity, foaming and emulsifying performance and solubility.
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The relationship of enzyme specificity to molecular size and hydrophobicity of hydrolyzed peptides is shown in figure 12, where long peptides, medium length peptides, short peptides react differently with hydrophobic and nonhydrophobic enzyme.
Figure 12: Relationship between the peptide character and the cosmetic efficacy
There are number of proteins present in the nature.Some of them present in the human body as shown in table 1.
Table 1: Three types of protein found in skin.
Types of protein Action
Keratin Provide strength, flexibility, made skin waterproof Elastin Made skin flexible but tight
Collagen Act as a cement, hold everything together
The protein ingredientsused in cosmetics are classified into following five categories -
1. Nonhydrolyzed protein - albumen, atelocolllagen, alciumcaseinate, casein, silk. protein serum, wheat germ protein, etc
2. Hydrolyzed protein - ammonium hydrolyzed protein, gelatin, lupine protein, silk, soy protein, etc.
3. Quaternized protein – cocamidopropyldimethylaminohydroxypropylhydrolysed collagen, triethonium hydrolyzed collagen ethosulfate, Hydrolyzed rice bran protein, etc.
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4. Condensates – AMP- isostearoylhydrolysed collagen, iodized hydrolysedzein, sodium succinoyl gelatin, etc.
5. Enzymes – amylase, bromelanin, catalase, glucose oxidase, lipase, papain, pepsin, etc.
Cosmetics are of different types such as skin care products, hair care products, cleaning products etc.The different protein derivatives are used in cosmetics as shown in table 2,3 and 4.
Table 2: Protein derivative used in skin care products Protein Derivative Skin Care products
Protein Hydrolysates Humectant,moisturizer,Film former, skin conditioner.
Gelatin Thickening agent, humectant, Skin protectant.
Soluble Collagen, serum albumin Skin moisturizer, Conditioner, Protectant.
Silk powder, Insoluble keratin powder Oil absorbent, cohesive agent, protectant.
Table 3: Protein derivative used in hair care products
Protein Derivative Hair Care products
Protein Hydrolysates (keratin, collagen) Hair conditioner, Buffering agent AMP- isostearoylhydrolysed protein Hair conditioner
Potassium undecylenoyl hydrolyzed collagen Antidandruff
Pottassiumabietoyl Hydrolyzed collagen Scalp lipid regulator
Table 4: Protein derivative used as cleansing agents
Protein Derivative Cleansing products
Protein hydrolysates (reticulin, oat protein) Anti- irritant, Moisturizer Desamido collagen, albumin Skin moisturizer, protectant Pottassium and sodium cocoylhydrolysed
(collagen, soy protein)
Detergent, foaming enhancer, anti- irritant Alkyldimoniumhydroxypropylhydrolysed
(collagen)
Anti-irritant, conditioner
The high buffering capacity of protein hydrolysates is used to stabilise the cosmetic preparation.
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Lather enhancer cellulosics in personal care products
The multi- functional family of water soluble polymers METHOCEL cellulose ethers are an extensive family of methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) polymers that are extensively used in personal care products. They are used as thickener in liquid formulation and as a binder in solid and semi solid formulations. Methocel products also act as film former, lubricants, lather enhancer and gelling agent in personal care products.
Alkyl ethoxylated sulfate, sodium and/or potassium salts, of coconut alkyl triethylene glycol ethoxylated sulfate, alkyl triethylene glycol ethoxylated sulfate, and tallow alkyl hexaoxyethylene sulfate are important lather enhancer used in the formulation of mild cleansing agent.
The commercial preparation BenecelTM E10M Hydroxypropyl Methylcellulose is highly pure, water soluble, non-ionic, cellulose ether. It is used in personal care products like shampoos, body washes, shower gels and shaving creams as a thickener, lather enhancer, water-binder, film former.
Application of polymers in hair care
The original uses of polymers in hair care were as a fixative and viscosity controlling agent, but nowadays, they are used as conditioning agent also. The commonly used polymers in hair care products are guar gum, cellulose, proteins, polypeptides, chitosan, lanolin, starches, sugars and amino silicones. Polymers are used as a primary ingredients or adjuncts in shampoos, conditioning products, mousses, styling products (lotions and gels) and hair sprays. The function of polymers in hair care products include conditioning, improving substantivety of other ingredients to hair, improving combing, manageability, curl retention, thickening formulations and improving emulsion stability.
The most important polymer used in hair care products are cationic polymer. Many commercially available shampoos use cationic surfactants and anionic polymers in their shampoos formulation. This leads to the neutralization of charges and excess cationic charges of surfactant can also be neutralized by using anionic surfactant rather than using anionic polymer.
The structure of cationic polymer shown below in figure 13.
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Figure 13: Structure of cationic polymer
The larger molecular weight polymers spread slowly onto hair than the smaller molecular weight polymers. Along with the molecular weight, charge also play very important role in the adsorbtion onto hair, the charged polymers adsorb faster than the uncharged polymers.
The maximum adsorbtion of polymer occurs at the pH 7, which is reduced at pH 4 and pH 10.
Applications of acetylene derived polymers for personal care
The German chemist invented the polyvinyl pyrrolidone (PVP) derived from acetylene in the process known as Walter Reppe Process. In this process, acetylene reacted with formaldehyde at high temperature and pressure to give butanediol, which is oxidised to give gamma- butyrolactone, which further reacts with ammonia to give 2- pyrrolidone. The Walter process shown in figure 14.
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Figure 14: Showing Reppe Process.
The 2-pyrrolidone react with many more acetylene group or methanol to give N-vinylpyrrolidone or methylvinyl ether series of polymers respectively. These types of polymer have film forming capacity and prove to be the important ingredient in hair styling products.
Lactam based polymers based on their functionality used in various personal care products like hair sprays, hair styling gels, hair conditioning agents, teeth whitening, toothpastes and water proofing sun creams.
Methods of evaluation for conditioned hair
“A hair conditioner is an ingredient or a product, thaton application improves the compatibility of hair relative to appropriate control”. The conditioning of hair is shown in figure 15.
Figure
15: Showing conditioning of hair.
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Evaluation methods for single hair fibres after treating with polymer solutions or dispersion of polymer containing cosmetic formulations are-
Surface Energy
The surface energy of the intact human fiber is determined by the outermost layer of epicuticle, which consist of covalently bound, long chain fatty acids. The surface energy of hair fibre surface is increased by the deposition of hydrophilic polymers, which can be determined and quantified through wettability measurements. Different method for measurement are-
(a) Wetting Force Measurement- Immersion Method.
(b) Wettability Measurement- Liquid Membrane Method.
1. Dynamic Electrokinetic and Permeability Analysis (DEPA)
This method provides information about the interaction between the active components of shampoo and conditioner formulation and hair. It is used to find out the ability or fingerprint of cosmetic formulation to modify or enhance the hair fibre surfaces.
2. Microfluorometry
Fluorescent reagents and dyes are used as a specific indicator to detect the presence of charged or reactive group of cosmetics into or onto hair. They are being used to determine the rate and extent of diffusion into fibre cross-sections (hair) where other methods of estimation such as absorbance measurements are not sufficiently sensitive.
3. Intercuticular cohesion
Due to various grooming processes, the cuticular layer of hair shaft lead to total damage resulting in the formation of split ends. This is the method to measure the semiquantitative cohesion of intercuticle in the outer most cuticle layer.
4. Frictional properties
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The electrostatic charges are developed during the combing of hair which is affected by the polymer deposition. The interfiber friction and adhesion are very important for hair volume, hair body and properties of hair. This method measures the frictional forces between the fiber and comb or fiber and fiber.
5. Interfiber adhesion
Interfiber adhesive forces play an important role in various deformation modes of fiber assemblies, such as bending and compression.
Organo-modified silicone copolymers for cosmetic use
The series of alkyl- substituted siloxanes included silicon hydrides. The synthesis of alkyl substituted siloxanes require suitable solvent using platinum catalyst and combining unsaturated α- olefins with silicon hydride compounds. This synthesis mechanism shown in reaction 1 R3SiH + R2’C=CR2’ R’CH-CR2 ‘-SiR3 ……… (1)
Alkylation of silicones enhance its character of moisturization and improve compatibility with other cosmetic raw materials. The alkylation of silicones provide enhancement in rheology, enhance product stability, lubricity in personal care products and it has been used to increase the volume of hair on its application.
Glycol functionality is useful for increasing the compatibility of silicones in polar media like terpolymers of dimethyl, methylalkyl, methylpoly ether functionality such as cetyldimethiconecopolyol, promote formation of triple phase emulsions and improve formulation stability. This property has been utilized in the cosmetic formulation from low viscosity lotions to thick creams as a rheology modifier.
Alkyl modified silicones act as an occlusive barrier on the skin, when used in sunscreen creams, skin care and colour cosmetic products. The high degree of alkylation or longer chain alkylation improve the water resistances properties of silicones. Alkyl modified silicones are available in different physical forms as shown below in table 5.
Table 5: Physical form of Alkyl Modified Silicones Polymers Silicones Polymers Physical Form
Decyldimethicone Liquid
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Lauryl dimethicone Liquid CetearylMethicone Soft wax StearylMethicone Brittle wax Stearoxydimethicone Hard wax
The benefits derived from alkyl modified silicones are moisturization, water resistance, rheology modification and emulsification.
Use of chitin and chitosan in Cosmetic
Chitin and chitosan are not naturally found in human skin but their presence on skin speed up the wound healing and minimizes scarring. Chitin can be used in the processing of film and fibers.
The chitin fibers are prepared by wet spinning in 14% sodium hydroxidesolution and used as non-allergic, deodorizing, antibacterial and moisture controlling in cosmetics. Chitin is very effective hydrating agent, it supplies water and it avoids dehydration and provide long lasting hydrating effects. Chitin and its derivatives allow active principles in close contact with the skin.
The structure of chitin and chitosan along with their difference shown below in figure 16.
Figure 16: Structure of Chitin and Chitosan.
Chitosan is the only naturally occurring cationic polysaccharides. Chitosan is a random copolymer comprised of two monosaccharides, N-acetyl-β-D-(1,4)-glucosamine and β- D-(1,4)- glucosamine generally in a 1:4 ratio in commercial materials. Chitosan and its salts have strong affinity to anionic surfaces of skin and hair. It is an important film forming polysaccharides which is being widely used in cosmetic formulation and hair shampoos. Chitosan also facilitates the formation of tensor film on the skin’s surface that can fix active ingredient for the skin.
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Therefore, chitin and chitosan are widely used in skin creams, shampoos, skin lotions, lacquers, varnishes, etc.
Cationic polysaccharides for cosmetics application
The cationic polysaccharides of cosmetic interest are of synthetically altered polysaccharides.
The cationic polysaccharides have been used as a damage control agent and as conditioner to skin and hair which are negatively charged. Only three cationic polysaccharides have commercial application in cosmetics namely cationic hydroxyethylcellulose, cationic guar, cationichydroxypropylguar. They are of different types like-
1. Naturally Occurring Cationic Polysaccharides
(a) Chitosan - It is the only naturally occurring cationic polysaccharides. Chitosan is a random copolymer comprised of two monosaccharides, N-acetyl-β-D-(1,4)-glucosamine and β- D-(1,4)-glucosamine generally in a 1:4 ratio in commercial materials. In cosmetic formulation the polysaccharides are often neutralized with a functional carboxylic acid such as lactic acid or glycolic acid and act as natural moisturizing agent found in skin.
The structure of chitosan shown below in figure 17.
Figure 17: Structure
Chitosan and its derivative have strong affinity to anionic surfaces like skin and hair.
These strong polysaccharides have mucoadhesive properties and it binds to the glycoproteins of moist body tissue such as those lining the eyes and throat.
2. Seminatural Cationic Polysaccharides
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(a) Cationic Hydroxyethylcellulose – Cellulose treated with alkylating reagent ethylene oxide under alkaline conditions produces water soluble cellulose derivative known as hydroxyethylcellulose (HEC). This is used as an aqueous viscosifier in personal care products. This viscosifying effect depends upon molecular weight of the cationic HEC (increasing molecular weight leads to increased solution viscosity).
(b) Cationic guar/ cationic Hydroxypropylguar – Guar gum is a naturally occurring polysaccharide that is commercially isolated from seeds of several leguminous plants.
Guar, like HEC can be cationically modified by alkoxylation with a quaternary epoxide to improve its cosmetic characteristics. Cationic guar as well as cationic hydroxypropyl guar are both interactive to anionic surfaces like skin and hair. Thus, both are widely used in shampoos and conditioners.
Assessment of polycationadsosrption
Cationic materials (surfactants and polymers) have been the traditional conditioners for keratinous substances like hair. The radiotracer method is used for studying the physical interactions (including sorption) of surfactants and polymers with hair. The limited surface area of natural keratins especially hair have the nominal value of approx. 0.1m2 /g.
The procedure followed for the adsorption of polycation is shown in figure 18:
1. Uptake of the polymer is substantial, exceeding 1% by weight in 60 min, 2. Initial adsorption occurs immediately.
3. Bleaching of hair has a major effect on the uptake of polycation, after 1 hr a threefold increase from 1.2% to 3.4%.
4. As the function of pH sorption was highest at pH 7.
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Figure 18: Adsorption of cation.
The nature, extent, and consequences of polycation sorption can all be influenced by the presence of surfactant. The non-ionic surfactants have small effect on the adsorption in comparison to cationic surfactants which have large effect because of the competition for the sorption sites. The surfactants are the most important and most interesting part of ingredient in the conditioning shampoos and body washes.
Alkylated Polyvinylpyrrolidone polymers in cosmetics
Polyvinylpyrrolidone (PVP) is manufactured by the free radical addition polymerization of N- vinyl-2-pyrollidone. PVP is a comb like structure with amide groups on every other carbon of the backbone. The delocalization of electron makes the amide carboxyl group electronegative and make PVP viscosifying and complexing agents in cosmetics. The structure of alkylated polyvinyl pyrrolidone is shown below in figure 19.
Figure 19: Structure of Alkylated polyvinyl pyrrolidone.
The cyclic nature of PVP amide functionality make it similar to the polyamide bonding of protein such as collagen in skin and keratin in hair. PVP provide excellent humectancy and lubriciousness to the formulation that provide softness and moisture to the skin. PVP are used as a film former, hair fixative resin, thickener, lubricant skin protectant, adhesion promoter and gelling agent in cosmetics used for personal care. The general application of Polyvinyl Pyrrolidone are given in table 6.
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Table 6: Application of Polyvinyl Pyrrolidone
products Application
Pharmaceuticals Binders, Disintegrating agents, suspending agents
Cosmetics Hair spray, lotions, Conditioning shampoos. suspending agents Food Stabilization in Beverages
Adhesives Adhesive sticks
