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Polymers in Hair Products
Abstract
Polymers have become increasingly important components of cosmetics over the past few decades. The original uses of polymers in hair care were as fixative agents and viscosity controlling additives; however, new polymers today are also used for hair conditioning and for the development of new style control products. Polymer substantivity to hair fibers increases with molecular size, with an increasing number of polar group attachments and especially with an increasing number of cationic groups for attachment to the negatively charged surface of hair fibers. From an anionic shampoo medium the cationic charge on polymers is neutralized and the adsorbing species is essentially a neutral or negatively charged species. The most successful silicone conditioning polymers for hair care have been used in both shampoo and conditioner compositions. Dimethicones in shampoos condition undamaged or lightly damaged hair better than they condition highly damaged, bleached hair or even tip ends because neutral hydrophobic conditioning agents adsorb more readily to an undamaged hydrophobic surface than to a damaged highly polar hair surface. New block co-polymers and a fairly large number of new cationic polymers have been introduced into hair care recently, while fractal polymers (highly irregular shapes) and nanoparticles have been developed and are receiving attention for potential use in hair care.
... Fouriertransform Raman spectroscopy has been used to differentiate between the rubbery state and the glassy state due to water vapor of such polymers [51]. The use of polymers in hair styling products has been reviewed [52,53]. ...
Knowledge of the surface of the hair is essential when dealing with the processes behind the adhesion of hair care cosmetic products. As a consequence of its biological origin, the structure and composition of hair fibers cannot be considered as homogeneous. Ethnical origins, exposure to environmental stresses, chemical and physical cosmetic treatments can lead to modifications in the physical chemistry of the hair surface. In this chapter we will provide a summary of current chemical and physical knowledge of the outermost hair surface. From a physical point of view, the hair surface is highly structured. The shape and orientation of the cuticle scales determine many aspects of the interactions and contact between fibers, between a fiber and the skin or between the fiber and a myriad of potential molecules that come into contact with the hair either from the atmosphere or from solutions of cosmetic products. We will show recent advances in the measurement of the forces at the hair surface using Scanning Probe techniques both on real hair samples as well as on physico‐chemical model surfaces. We will conclude with a review of the macroscopic surface properties as well as a discussion about their influence on consumer sensorial perception.
Introduction:
Dosing regimens requiring multiple daily applications frequently result in poor patient compliance, especially in the treatment of chronic skin diseases. Consequently, development of sustained delivery systems for topical drugs permitting less frequent dosing is of continuing interest for dermatological therapy. Areas covered: This potential of polymeric film-forming systems (FFS), created in situ on the skin, as sustained delivery platforms for topical drug delivery is reviewed. Key formulation parameters that determine delivery efficiency are considered focussing on those that permit a drug reservoir to be established in the upper layers of the skin and/or on the skin surface from which release can be sustained over a prolonged period. The advantageous and superior cosmetic attributes of FFS (compared to conventional semi-solid formulations) that offer significantly improved patient compliance are also addressed. Expert opinion: The promise of polymeric FFS as convenient and aesthetic platforms for sustained topical drug delivery is clear. Manipulation of the formulation allows the delivery profile to be customised and optimised to take advantage of both a rapid, initial input of drug into the skin (likely due to a transient period of supersaturation) and a slower, controlled release over an extended time from the residual film created thereafter.
Cyclical extension stresses in dry hair at strain levels between 7% and 15% were seen to produce localized cuticle decementation and buckle formation at the cuticle edges. The experiments show that this type of damage results from circumferential compression stresses on the dry cuticular envelope that acts as a rigid thin-wall pipe during the process of Poisson contraction as the fiber is being elongated. Higher cyclical extensions (>25%) were seen to result instead in cuticle lifting with no buckle formation. This latter type of cuticle damage is similar to the one observed by Reutsch et al. and was already ascribed to the action of longitudinal shear stresses. When the hair was moistened or solvent-swollen, no damage was observed at each individual cuticle; instead, long deep transversal cracks and decementation of the whole cuticular envelope from the cortex were observed. The experiments indicate that the lack of individual cuticle damage under swollen conditions results from a strengthened hydrogen-bonding crosslinked endocuticle and from a lesser fiber Poisson contraction when the fiber is swollen. Cuticle buckling and decementation at the cuticle edges like those described above were also frequently found in the hair of a panel of 100 individuals. The prevention and repair of this type of damage is also discussed.
Fluorescence spectroscopy, combing analysis, and texture analysis with a dual-cantilever bending accessory have been employed to study the effect of pretreatments on the thermal damage of hair. The pretreatments, applied to hair as 1% aqueous solutions, included a cationic polymer (PVP/DMAPA acrylates copolymer), a protein hydrolyzate (hydrolyzed wheat protein), and a cationic surfactant (quaternium 70). Fluorescence spectroscopy was used to probe the content of tryptophan (Trp) in hair, which is gradually destroyed by the application of curling irons at 132°C and 152°C. All pretreatment materials were found to reduce the extent of Trp decomposition by 10-20% as a result of 4-12 min of thermal exposure. Surface damage has been quantified by combing analysis and has shown that the use of PVP/DMAPA acrylates copolymers or a cationic surfactant can suppress an increase in combing forces, which is observed in unmodified hair subjected to thermal exposure. The variation in stiffness of hair tresses has been studied by texture analysis with a dual-cantilever bending accessory. From the texture analysis, an increase in the stiffness ratio of the fiber assemblies was evident for polymer-modified and intact (unmodified) hair.
Cycles of wetting and blow-drying were applied to hair fibers and resulted in the formation of multiple cracks on the hair cuticles. The peculiarity of these cracks was that they always appeared aligned parallel to the longitudinal axis of the hair fiber. The cracks appeared to be initiated at the end of the cuticles close to the cortex and propagated invariably towards the outer cuticle edges. The maximum growth length of each crack was seen to be limited to the size of one cuticle. Crack formation did not only occur at the outer edges of the cuticles but also took place in the second and third overlaid hidden cuticle sections. The results show that these cracks form when the external portions of the cuticles undergo drastic reduction in their hydration water. Under these conditions the outer cuticle portions become rigid and brittle and crack by the action of circumferential tension stresses arising from the swelling pressure of both the cuticle layers underneath and the cortex itself. Hair cuticle analysis from a panel of 100 individuals showed that these cracks are present in the hair of people who commonly blow-dry their hair and appear to a much lesser extent in the hair of subjects who do not practice this type of grooming process. The combing of hair fibers presenting this type of cracking was seen to result in the breakage of large portions of cuticle. The effect of some cosmetic actives on the formation of these cracks is also discussed.
Aqueous solutions containing poly(vinyl-pyrrolidone) and sodium caprylate, or poly(vinyl-pyrrolidone) and tetraethylammonium perfluorooctanesulfonate,respectively, have been investigated by volumetric, ionic conductivity and surface tension methods. The presence of an interaction region has been determined from conductivity and surface tension. The width of such a region depends on the amount of polymer in the mixture,temperature, surfactant content and added electrolyte (NaCl). The observed behaviour was explained in terms of the combined effects played by the alkyl-chain hydophobicity, polar head group(s) and counter-ions.
An approximate solution to a mass action model for the binding of surfactants onto polymers has been introduced. It allows determining the width of the interaction region as a function of polymer mass percent in the mixture.
We have compared the interactions between Polyquaternium 10-mixed surfactant micelle complexes of sodium dodecyl sulfate and Octoxynol with comparable complexes of mono-and diquaternary aminoalkylcarbamoyl cellulose derivatives. The methods utilized were precipitation studies, fluorescence, and dynamic light scattering. The results of the fluorescence study indicated that micellar regions were formed in the polymer-mixed surfactant micelle complexes. Temperature studies indicated that the Polyquaternium 10-mixed surfactant micelle complex exhibits a different temperature response than complexes formed with polymers synthesized in our laboratories.
Synopsis A method for measuring the adhesive strength of hairspray bonds joining individual hair fibers has been developed. The method involves application of 0.7 Ixl of hairspray to the overlapping portion of a hair loop and breaking the resulting junction on a tensile tester. Junction strength depends on polymer concentration , polymer type, and formulation variables such as the type of neutralizer used or the presence of plasticizers. Relative humidity may also have a significant effect on junction strength, depending on the polymer system used. Optical microscopy shows that failure of hair-hairspray junctions is usually adhesive failure rather than cohesive failure of the resin itself. Often a replica of the hair cuticle scale is left in the hairspray resin after bond breaking. However, some resins shatter when the bond breaks, still leaving cuticle imprints in pieces of resin, indicating that both cohesive and adhesive failure may have occurred.
Synthesis of a number of organomodified silicone resins is described herein, along with their subsequent evaluation in various personal care applications. Alkyl-modified siloxysilicates were found to impart volumizing benefits to hair conditioners without increasing combing forces. The extent of the volume enhancement was dependent upon alkyl chain length. Maximum tress diameter was found to increase with increasing alkyl chain length above C 16. Resins modified with olefins having chain lengths of C 10 or less did not function as volumizing agents. Styryl-functional siloxysilicates increased apparent luster or shine of hair, while polyether-modified silicone resins were found to offer set retention benefits for hair and to function as oil-in-water emulsifiers. It is anticipated that these materials may be designed to act as water-in-oil, or water-in-silicone emulsifiers by altering the polyether moiety and degree of polyether substitution. Several ester-functional siloxysilicates were evaluated for substantivity and found to resist water wash-off, suggesting use in skin care and color cosmetic applications. The ester materials were also found to provide a mild conditioning benefit to hair.
A new method, termed dynamic hairspray analysis, was developed to study the mechanical behavior of pre-set hair tresses, untreated and modified by hairspray resins, under a wide range of bending deformations. The technique includes a vertically acting tensile meter designed to measure the force in both compression and extension modes. The instrument, including a sample holder and spraying devices, was housed in an environmental chamber equipped with a humidity controller. The drying of a hairspray was investigated by (a) applying low intermittent deformations to a preformed hair tress in order to determine the properties of untreated hair, (b) treating the fibers with a hairspray, and (c) measuring the changes both in adhesive properties of a hairspray solution on the surface and in mechanical stiffness of the fiber assembly as a function of drying time. This approach allows the simultaneous determination of parameters such as stiffness of untreated and resin-modified hair, duration of tack, maximum value of tack force, and time of drying. In addition to this, the data collected during the experiment provide information about changes in geometrical dimensions of hair after the application of hairspray and after subsequent drying. In order to test the resistance of fixative resins to high humidity, the kinetic measurements of stiffness and tackiness were also performed at 90% RH.
Commentary on errors in an earlier article on the nature of the chemical bond. Keywords (Audience): First-Year Undergraduate / General
Sorption of Polymer JR, a cationic cellulose ether, by human hair is greatly decreased in the presence of added electrolytes. This reflects the competition between cations of the added salt and the quaternary ammonium groups of the polymer for sorption sites in the substrate. In this respect the hair can be regarded as a “strong-acid” ion-exchanger, and it displays a selectivity to ions similar to that observed for conventional resin exchangers. Cations can be ranked in order according to their ability to decrease the sorption of Polymer JR as follows:
La ⁺⁺⁺ > Al ⁺⁺⁺ < Fe ⁺⁺⁺ < Ca ⁺⁺ < Fe ⁺⁺ < Cs ⁺ < Na ⁺ < Li ⁺ .
Salts also promote desorption of Polymer JR that is already sorbed by hair. However, selectivity is less evident in desorption than in sorption and is only observed at relatively low concentrations of salt. About half of the sorbed polymer is readily removed by salt solutions; the rest appears to be tightly attached to the substrate.
The effect of oil viscosity, as well as the type and concentration of emulsifiers, on the deposition of nonionic silicone oils from oil-in-water emulsions on both untreated and cationically modified human hair was investigated. The emulsifiers in the ionic emulsions consisted of a mixture of either sodium octadecyl sulfate (SODS) or cetyltrimethylammonium bromide (CTAB) in conjuction with the two nonionic, ethoxylated nonylphenol surfactants employed in neutral emulsion systems. At constant oil viscosity, the rates of deposition were found to decrease with increasing nonionic surfactant concentration. At constant surfactant concentration, increasing oil viscosity gave rise to increasing rates and extent of deposition. Incorporation of ionic surfactants into the emulsifier systems results in corresponding changes in the zeta potentials of oil droplets, and consequently leads to shifts in the rates of deposition on untreated (negatively charged) or cationically modified keratin surfaces. The deposition data are discussed in relation to oil droplet size, zeta potential, and viscosity.
The interaction of a water-soluble cationic substituted cellulose ether with sodium dodecyl sulfate (SDS) has been examined through a study of precipitation patterns and measurements of surface tension, foaming, and electrophoretic mobility. In addition, the effect of this polycation in the subsolution underlying a spread monolayer of sodium docosyl sulfate (SDCS) has been investigated using force/area measurements. Addition of SDS to the polymer in solution results in progressive reduction of both its solubility and electrophoretic mobility, with maximum precipitation being close to the point of zero mobility. Increasing the surfactant concentration beyond this point results in resolubilization of the precipitate and increasing electrophoretic mobility in the opposite sense. Surface tension studies show that addition of the polymer, itself weakly surface active at the air/water interface, can result in large reductions in the surface tension of an SDS solution. Correspondingly, substantial increases in foam stability can result. The presence of the polymer in the subsolution results in penetration/adsorption into a monolayer of SDCS and a pronounced change in its force/area characteristics. The results are interpreted in terms of a highly surface-active polymer/surfactant complex resulting from “head to head” adsorption of the surfactant onto the polymer. Resolubilization occurs by “tail to tail” adsorption of a second layer of surfactant ions to form a polyanion.
The sorption of a cationic cellulose ether by bleached hair as a model keratinous substrate has been studied by a radiotracer method. The sorption process is characterized by a rapid initial uptake of polymer, followed by a much slower increase that can take a week or more to reach equilibrium. The sorbed amount is over 6% of the weight of the substrate for a solution concentration of one percent. The data are consistent with a mechanism involving penetration of polymer into the hair shaft. Surfactants cause a reduction in the amount of polymer sorbed. Among those studied were a nonionic ethoxylated secondary fatty alcohol, the anionic sodium lauryl sulfate, and the cationic myristyldimethylbenzylammonium chloride. Amounts of reduction caused by these materials varied widely, the greatest effect being with the cationic.
The sorption of tryptophan onto human hair from aqueous solution at pH 6 and room temperature was determined spectrophotometrically by depletion analysis. The sorption isotherm may be described by a modified B.E.T. equation, and the results indicate a multimolecular sorption which is probably caused by London forces between the tryptophan indole group and the aromatic keratin side-chains.
An irreversible penetration of [ ¹⁴ C] polyethylenimine into a human hair was demonstrated by radioactive-tracer technique. Under ambient conditions, 1% of the imine diffused into the hair in an hour. Desoprtion of the imine was rather slow; most of the imine could not be washed out by an untagged imine solution in 24 hr indicating a possible strong interaction between the imine and the hair. The results are assumed to be applicable to the untagged imine. The swelling rate of hair in distilled water and the swelling behavior of hair in the imine were studied by light micro scopic observation. When dry hair was wetted with deionized water, a 36 ± 7% swelling was found in 24 hr. The degree of hair swelling by the imine was much greater at pH 7 than at higher pH.
The effect of pH, concentration, and temperature on the swelling of the hair in the imine and some aspects of the permanent-waving mechanism by using the imine have been postulated and discussed.
Some of the limitations inherent in the use of directly measured contact angles for.the determination of filament wetta bility are discussed, and an alternate approach based on the Wilhelmy balance principle is presented. Mathematical interpretation of data obtained allows for determination of wettable cross-sectional areas in addition to wettability values. The technique has been utilized to demonstrate the effects of several process variables on the surface character of synthetic fibers.
The rate-limiting step in the heterogeneous reaction between the disulphide cross-links of hair keratin and alkaline mercaptan solutions was found to be diffusion of the mercaptan species through the fibre. Mercaptan diffusion rate and fibre swelling proved to be highly pH dependent over the pH range 2-11, the pH dependence varying markedly with the ionic character of the additional functional group attached to the mercaptan. Classically held concepts of electrostatic interactions and heterogeneous disulphide bond cleavage were used to interpret the diffusion and swelling results.
A principal difference between the interaction of cationic and anionic surfactants with polyglycol ethers has been found from measurements of surface tension, conductivity, dye solubilization, and the effects of change in pH of the media. Due to this experimental background, the following hypothesis of interaction between ionic surfactants and polygylcol ethers in water is stated. In water, only weak reversible hydrophobic bonding between cationic surfactants and polyglycol ethers is formed, increasing with hydrophobic character of the hydrophobic surfactant group and a decrease in temperature. Unlike cationic surfactants, complexing of anionic surfactants with polyglycol ethers is very marked. Here, besides hydrophobic bonding, electrical forces seem to be very important. The interactions are probably due to a partially positive charge transfer to the ether oxygen group and, consequently, an increased attraction of the hydrophilic group of the anionic surfactant.
The theory of diffusional release of a solute from a polymeric matrix where the initial loading of solute is less than or greater than the solubility limit has been reviewed and extended. The conceptual model for the saturated case proposed by Higuchi has been refined to remove the inaccuracies caused by the “pseudosteady-state” assumption. A finite external mass transfer resistance has also been incorporated into the present analysis. For all solute loadings, the asymptotic release profile is seen to be a linear plot of total amount of solute released versus the square-root of time which has a finite intercept on the square-root of time axis because of the external resistance. The dependence of the slope and intercept on solute loading and other system parameters can be predicted for all cases with the models presented. Experimental release rates of an organic dye from a silicone polymer into acetone were measured for a range of solute loadings in order to test the applicability of these equations. All system parameters except the external mass transfer coefficient were measured by independent experiments. The experimental release data were described very well by the computed results.
A simple method to quantify hair damage during combing or brushing has been developed. The method involves collecting hair fragments that are chipped from hair during combing and quantitatively measuring the amount of protein using a colorimetric procedure capable of detecting as little as 5 Ixg of protein per mi. Using this procedure on hair tresses in the laboratory and on live heads (half-head tests), we were able to demonstrate significant differences in protein loss during post-shampoo combing of undamaged and chemically damaged hair previously treated with various shampoos/conditioners. The method is applicable to different types of hair tested, namely, Caucasian, Asian, Oriental and Negroid.
copolyol with low hydrophilic-lipophilic balance (HLB), and amodimethicone. In this work, the condi- tioning effects of these silicones are discussed in terms of the surface deposition and alteration in hair surface characteristics by measuring the kinetic frictional coefficient of hair fibers in relation to the chemical types and the molecular weight of silicones. The improvement in surface kinetic characteristics was primarily noted with dimethicones with high molecular weight. Dimethicone copolyol with low HLB lowered the kinetic friction of the wet hair surface by forming liquid crystals. Amodimethicone improved manageability of hair by adsorbing strongly onto the damaged, and therefore more polarized, hair cuticles, which facilitated hair styling without blow-drying.
Synopsis-THIOGLYCOLIC ACID (TGA)-CUMENE HYDROPEROXIDE (CHP) and BISULFITE--CHP systems are described for po)ymerizing METHYL METHACRYLATE (MMA) in HUMAN HAIR. An ethanol-water solvent system was employed. Diffusion rate control appears to predominate over a variety of reaction conditions. The influence of reagent concentrations and so)vent effects on the reaction is also describe:). POLY- MERIZATION is shown to occur more rapidly into either reduced-oxidized or bleached hair than into chemically unaltered hair. Partial hydrolysis of the hair fibers containing polymethyl methacrylate (PMMA) provides filament-like fragments, consisting primarily of PMMA, which were examined microscopically.
Silicones, especially dimethicone and dimethiconol of higher molecular weights, have gained acceptance as conditioning agents and are used in several commercial products, frequently in conjunction with quats. In this work, the conditioning benefits of the silicones, as assessed by improvement in wet and dry combing, were investigated as a function of molecular weight as well as amount deposited on bleached hair. In addition, the combing performance of a quat was evaluated for the purpose of comparison, and its influence on the silicones, as pertaining to deposition and combing performance, was assessed. All the silicones improved wet and dry combing performance substantially over untreated hair. Their performance was greater than that of the quat for wet combing but was comparable for dry combing. The higher molecular weight gums showed slightly improved dry combing performance over the lower molec- ular weight fluids, but there was no significant difference between them for wet combing. Presence of the quat increased the amount of silicone depositing on the hair. A synergistic effect of the two was seen in that a significantly greater wet combing performance was displayed than was observed for the silicone or the quat alone. This phenomenon occurred for all of the silicones tested and was not observed for dry combing performance.
Samples of hair from five different female Caucasians were selected, while attempting to eliminate or minimize variables introduced by factors, suggested in previous literature, related to genetics, malnutrition, and cosmetic alteration, to analyze for 18 amino acids. The objective was to determine if human hair from such a similarly sampled group differs in composition from individual to individual. Significant differences were found for 9 of the 18 amino acids analyzed at the α = 0.01 level, however, the percent deviations for 16 of the amino acids were within ± 6%. Comparison of these samples of hair with pooled dark brown hair, from female Causasians, and purchased from a hair dealer, indicated a note-worthy difference only in the cystine content. Comparison of these data from human hair with that from 64's Merino wool indicates substantial differences between cystine, glycine, tyrosine, and phenylalanine. Statistically significant differences were suggested for other amino acids between Merino wool and human hair; however, the magnitude of the numerical differences, in these instances, was substantially lower than for the above mentioned four amino acids. Weathering effects in human hair were also explored, suggesting degradation to the amino acid residues of cystine, tyrosine, hysine, and histedine by the elements.
Bogaty (5) has suggested that hair frequently assumes a helical coil configuration in the course of its being combed into style. Curl holding, previously described, has generally not taken these torsional configurations into consideration in analysis of test results. This paper will present a new performance test, Twist Retention Analysis (TRA), for evaluating hair fixatives, utilizing torsional measurements of hair/resin composites under humid conditions. Evaluation is automated with the use of a Torsional Braid Analyzer. It will be demonstrated that Twist Retention Analysis is a precise measurement of the set holding capacity of hair fixatives, permitting the use of a small sample size in order to obtain statistically significant conclusions.
SPRAY k-ILMS are described. The scanning electron microscope is an invaluable tool for studying the COATABILITY of hair spray films on individual or small groups of hair libors. Coatability can be improved by addition of certain SURFACTANTS to hair spray formulations and can be correlated qualitatively to hair spray properties such as luster, ap- Iearance, and flaking. Coatability does not correlate well with curl retention, another important property of hair sprays, which is much more dependent on the physical properties of the resin. Previ- ous methods for evaluating curl retention were inadequate; therefore, a STATISTICAL APPROACH was developed. The method described is reliable, conclusions can be validated with a high degree of confidence and with these benefits, formulations can be optimized.