Formulations and uses thereof

Abstract

The invention relates to a composition comprising a fluorescent whitening agent or optical brightener of formula (l) or (II) and adjuvants for personal care applications. The structure of formula (l)

Description

TECHNICAL FIELD The present invention concerns the use of fluorescent whitening agents or optical brighteners for personal care products, for example in the whitening and the preservation thereof. BACKGROUND Fluorescent whitening agents (FWAs) or optical brighteners are chemical compounds that absorb light in the ultraviolet and violet region of the electromagnetic spectrum and re-emit light in the blue region. FWAs or optical brighteners are used to enhance the appearance of different materials, by causing a "whitening" effect, making materials appear a brighter white colour by increasing the overall amount of blue light emitted. Although expensive, FWAs or optical brighteners can be used at low cost due to their effectiveness at low loading levels. Current industry standard FWAs or optical brighteners, include DSPB (CAS 27344-41-8) and derivatives of the bis-benzoxazole type, such as the bis-benzoxazolyl-stilbene, OBI (CAS 1533-45-5), and the bis-benzoxazolyl-thiophene, OB (CAS 7128-64-5). These molecules have large conjugated aromatic systems of a high molecular mass, which have limited capability to be oxidised or hydrolysed, making them less biodegradable. In the personal care sector, FWAs or optical brighteners have been used to enhance the properties of product performance or the products themselves. Typically, this is achieved by either acting as whiteners or brighteners to improve the overall colour of the product itself or the colour of skin, hair, or teeth, or by acting as UV absorbers or filters, which can protect the product, or in the case of sunscreen, the user themselves. As an example, one application is in formulas for washing and conditioning white, grey, or blonde hair, where the FWA or optical brightener can not only increase the luminance and sparkle or shine of the hair, but can also correct dull, yellowish discoloration without darkening the hair. Another application is in pigments or dyes in the colour cosmetic space, particularly for face and eye powders, where the FWA or optical brightener adds an additional dimension to the colour which can brighten shadowed or dark areas of the skin. The use of fluorescent materials in cosmetics is known. For example, there are a number of reported uses of fluorescent pigments or dyes in cosmetics, particularly in colour cosmetics, principally to impart an additional dimension to the colour. For example, in EP370470 and US5635109, the fluorescent materials are used to intensify colour or shine imparted by a cosmetic composition, such as a nail lacquer, a lipstick, or a hair cuticle coat. Additionally, US6313181 describes cosmetic compositions comprising a fluorescent-effective amount of at least one fluorescent brightener, in combination with a cosmetically acceptable vehicle, where the compositions are used as colour cosmetics and skin treatment products, to replenish the skin's natural fluorescent glow. Two of the most commonly used optical brighteners in the personal care sector are DSBP and OB. DSBP is used in multiple personal care products, including soaps, shampoos, skin creams, and the like, with well-known brands such as Sanex™ and Clinique™ adding the compound to their products. OB is used as a colourant, in some skin conditioning products. The conventional FWAs or optical brighteners used in the personal care sector have several disadvantages, including that they are conventionally manufactured from fossil fuel derived sources, they are typically non-biodegradable, and they are typically toxic to the aquatic environment. There has therefore been a move to develop FWAs or optical brighteners that are biodegradable and produced from renewable sources. For example, CN114507230 describes a bicyclic pyridone derivative, as well as a synthesis method and application thereof. The bicyclic pyridone compound and the derivative thereof can be synthesised through cheap and low-toxicity citric acid, the production cost is low, and the synthesis process is simple. Additionally, CN110330496 and CN109438479, describe ultraviolet light absorption materials, and preparation methods and applications thereof. The UV absorbent materials are derived from pyridone compounds and have applications in a variety of fields, such as ultraviolet light absorption aqueous coatings, sunscreen cosmetics, and fluorescent brighteners. In CN110330496, the compounds are metal salts of a pyridine ketonic acid, enabling good solubility properties. In CN109438479 the compounds are functionalised with flexible alkyl chains and water-soluble groups to change the water solubility and the dispersibility of the absorber inside polymers. Our co-pending international application, PCT / EP2024 / 056098 (published as WO / 2024 / 184492) discloses biodegradable fluorescent whitening agents for use in laundry applications based on pyridone derivatives, which have fewer environmental drawbacks. The present invention seeks to overcome the aforementioned disadvantages and provide improved FWAs, or optical brighteners optimised for personal care applications, with comparable functionality and fewer environmental drawbacks. SUMMARY OF THE INVENTION According to a first aspect of the invention, there is provided a composition comprising a fluorescent whitening agent or optical brightener of formula (I) for use in personal care, comprising at least one fluorescent whitening agent or optical brightener of formula (I) and adjuvants, wherein the fluorescent whitening agent or optical brightener of formula (I) has the structure: Y^.0 o^n^y 'A' (I), wherein: A is C(R1R2)(CH2)n wherein R1 is H, CH2OH or COY, R2 is H or CH2OH and wherein n is 1 or 2, or wherein A is an optionally substituted aromatic or heteroaromatic ring fused with N and X wherein N and X are respectively bound to adjacent carbon atoms on the ring; Xis O, SorNR3; the or each Y is independently OM, OR3, O(CH2)qSO3M, NHOH, NHR3, NR32, or X'L, wherein, M is selected from an alkali metal or an alkaline earth metal; the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units; q is 1 to 5; and alternatively, NR32 represents a heterocyclic ring; when Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to at least one repeating unit of formula (I) having X' as defined above in place of Y. In particular embodiments, the FWA or optical brightener of formula (I) may be of formula (la): wherein Z may be O, or -NH; X may be S, O, or -NR3; the or each R1 may be independently H or -C(O)ZR3; and the or each R3 may be independently selected from hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units; wherein, when the or each R3 is a linear alkyl, it is a C7-C34 alkyl, and when the or each R3 is a branched alkyl, it is a C1-C34 alkyl. In particular embodiments, the FWA or optical brightener of formula (I) may be selected from formula (lb), or formula (Ic): wherein Z may be O, or -NH; X may be S, O, or -NR3; the or each R1 may be independently H or -C(O)ZR3; and the or each R3 may be independently selected from hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units. According to a second aspect of the invention, there is provided a composition comprising a fluorescent whitening agent or optical brightener of formula (II) for use in personal care, comprising at least one fluorescent whitening agent or optical brightener of formula (II) and adjuvants, wherein the fluorescent whitening agent or optical brightener of formula (II) has the structure: Y^.0 O^N^O R (II) wherein: R is H, CHR5R6, R5, R6, an alkylsulphonate, a polyether, an optionally substituted aromatic or heteroaromatic ring, CH2COY or CH(COY)((CH)nCOY) in which each Y is the same or different; the or each Y is independently OM, OR3, O(CH2)qSO3M, NHOH, NHR3, NR32, or X'L, wherein, M is selected from an alkali metal or an alkaline earth metal; the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units; q is 1 to 5; alternatively, NR32 represents a heterocyclic ring; when Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (II) having X' as defined above in place of Y; and R5 and R6 independently represent hydrogen, alkyl, alkenyl, vinyl, phenyl, hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl, aminomethyl, l-(dimethylamino)methyl, 2-(dimethylamino)ethyl, 5-aminopentyl, or cyano, optionally wherein R4 and R5 are the same or different, and n is 1 or 2. The composition may comprise a multiplicity of different FWA or optical brightener compounds, which may preferably be according to structures (I) and / or (II). In most preferred examples, the polymer composition may comprise a multiplicity of different FWA or optical brightener compounds, and all of the compounds may be according to structures (I) and / or (II). For example, the composition may comprise at least one, at least two, at least three or at least four different FWA or optical brightener compounds according to the invention. The adjuvants may be any cosmetically acceptable carriers or auxiliaries. The addition of further adjuvants or components may be necessary to further compatibilise the fluorescent whitening agent or optical brightener with the composition, or to modify the final composition's properties for a particular application, such as personal care, for example. The FWA or optical brightener may be biodegradable. According to a third aspect of the invention, there is provided a formulation of the composition according to the first or second aspect of the invention for use as a personal care product. The FWA or optical brightener may be formulated in combination with further adjuvants, additives, and / or components to alter and / or control the properties of the formulation or composition. The personal care product may be selected from any of, but not limited to, the following; leave on or off rinse off products, haircare products, skincare products, nail care products, oral care products, or UV-protection products. Examples of such products may include, but are not limited to, shampoos, conditioners, styling products, colour cosmetics, soaps, face and body washes, deodorant, skin creams, sunscreens, depilatories, nail varnishes, toothpastes, dental products, wax-based products, and the like. The aforementioned products may be provided in any suitable format, such as for example, as emulsions, dispersions (such as gels), balms, oils, solutions, aerosols, or powders. According to a fourth aspect of the invention, there is provided the use of the composition according to the first or second aspect, or the formulation according to the third aspect, in a personal care product. According to a fifth aspect of the invention, there is provided a personal care product comprising a fluorescent whitening agent or optical brightener as defined according to the first or second aspect of the invention. Any feature discussed in reference to one of the aspects of the present invention applies equally to all of the other aspects discussed herein. DETAILED DESCRIPTION Fluorescent whitening agents (also referred to as FWAs) and optical brighteners, are additives widely used in the personal care industry to enhance the whiteness, brightness, and visual appeal of various products, and / or the appearance of the surface to which they are applied. FWAs are compounds that absorb invisible ultraviolet (UV) light and re-emit it as visible blue light (wavelength 400 - 500 nm), making cosmetic products or bodily surfaces look whiter or brighter. This effect compensates for the natural yellowish cast of many cosmetic ingredients, or for the shadowed or dull or brassy tone of skin or hair, improving both perceived whiteness, lightness, brightness, or lustre. Current industry standard FWAs and optical brighteners, including OB and OB-1, have large conjugated aromatic systems of high molecular mass, which have limited capability to be oxidised or hydrolysed, making them less biodegradable. As a result, current industry standard FWAs are raising environmental concern as they are not only detected as pollutants in urban wastewaters (Marine Pollution Bulletin, 2022, 178, 113559) but also in indoor environments (Environ. Sci. Technol., 2022, 56,10131-10140. In the personal care industry, where products often either end up in wastewater or in landfill, it is key that FWAs and optical brighteners are environmentally friendly. Pyridone and citrazinic acid derivatives are known to achieve similar n-electron counts to the large conjugated aromatic systems of industry standards and also emit visible blue light in the 420 - 470 nm range, whilst also being bio-derivable. These derivatives, which have substantially lower molecular weights, achieve this effect through the incorporation of heteroatoms, such as nitrogen and oxygen. Therefore, the pyridone and citrazinic acid derivatives of the invention can be synthesised through cheap and low-toxicity starting materials, meaning that the production cost is low, and the synthesis process is simple. Properties of Fluorescent Whitening Agents According to the invention the composition comprises at least one compound of structure (I) or (II) as a fluorescent whitening agent or optical brightener. The excitation and de-excitation properties of the FWAs or optical brighteners in accordance with the invention may be mechanistically understood with reference to prior art studies, such as Sci. Adv., 2015, 5, 34795, which attributes the fluorescence in the 420 - 470 nm range of similar compounds to n*- n transitions in the same carbon-oxygen double bond, as is found in scaffolds based on pyridone and citrazinic acid. The carboxyl groups, particularly the carboxylic acid groups, present in the structures of the present invention are believed to contribute to the required number of n-electrons associated with fluorescence in the desired range. The FWA or optical brightener compounds contained within the formulations or compositions of the invention are advantageous over current industry standards as they provide comparable fluorescence using a smaller compound, with a lower molecular weight. Additionally, further functionalisation of the compound formulae to modulate end-application performance may be readily achieved, with little effect on the overall fluorescent behaviour of the fluorescent whitening agent or optical brightener. Additionally, the smaller molecular weight, can lead to a lower loading of the FWA or optical brightener in the final formulation or composition. Lower loadings can mitigate any potential adverse effects associated with the compound, which may be important in personal care products when seeking regulatory approval. Additionally, the FWAs or optical brighteners in the compositions in accordance with the invention have smaller fluorescent cores and are thus more biodegradable as they are more prone to biological attacks, whilst still providing enough stability to oxidation and hydrolysis to be of use in the intended applications. In embodiments of the invention, the molecular weight of the FWA or optical brightener compounds may be below about 1500 Da, below about 1250 Da, below about 1000 Da, below about 750 Da, below about 500 Da, below about 400 Da, below about 300 Da, or below about 250 Da. In embodiments of the invention, the molecular weight of the FWA and optical brightener compounds may be from about 250 Da to about 1500 Da, from about 250 Da to about 1250 Da, from about 250 Da to about 1000 Da, from about 250 Da to about 750 Da, from about 250 Da to about 500 Da, from about 250 Da to about 400 Da, or from about 250 Da to about 300 Da. In preferred embodiments, the molecular weight of the FWA and optical brightener compounds is below about 500 Da. In embodiments of the invention, the quantum yield of the FWA or optical brightener compounds may be at least about 30%, at least about 40%, at least about 50%, at least about 60%, or at least about 70%. In embodiments of the invention, the quantum yield of the FWA and optical brightener compounds may be from about 30% to about 100%, from about 30% to about 80%, from about 40% to about 80%, from about 50% to about 80%, from about 60% to about 80%, or from about 70% to about 80%. In preferred embodiments, the quantum yield of the FWA and optical brightener compounds is at least about 60%. As used herein, the term "quantum yield" will be understood to mean the ratio of the number of photons emitted to the number of photons absorbed. Therefore, the quantum yield is a dimensionless quantity representing the efficiency of a light-induced process, such as fluorescence. Advantageously, the FWAs or optical brighteners of the present invention exhibit much higher relative quantum yields than current industry standards. For example, only DSPB gives a comparable value of greater than 70%. As a result, the FWAs or optical brighteners contained within the formulations or compositions of the invention are advantageous over current industry standards as they provide comparable or enhanced fluorescence whilst using a smaller compound, with a lower molecular weight. Additionally, further functionalisation of the structures of the invention to modulate application performance may be readily achieved, with little effect on the fluorescent behaviour of the FWA or optical brightener. Additionally, the FWAs or optical brightener compounds contained within the formulations or compositions according to the present invention, have excellent chemical stability at over a broad range of pHs and have high thermal stability. The FWA or optical brightener may be stable at a pH of about 4 to about 9, about 5 to about 8, or about 6 to about 7. In the present invention the in-use pH of the FWA or optical brightener is preferably in the range from pH about 4.5 to about 7.5. A pH in this range is particularly beneficial for adsorption of FWA or optical brightener surfactants, to hair for example. In particular examples, such as shampoos, the pH may be from about 4.5 to about 7.5, whereas in conditioners, the pH may be from about 3.5 to about 5.5. Chemical Structure of Fluorescent Whitening Agents According to the invention, the FWA or optical brightener is of formula (I) or (II): When the FWA or optical brightener is of formula (I): A is C(R1R2)(CH2)n wherein R1 is H, CH2OH or COY, R2 is H or CH2OH and wherein n is 1 or 2, or wherein A is an optionally substituted aromatic or heteroaromatic ring fused with N and X wherein N and X are respectively bound to adjacent carbon atoms on the ring; Xis O, SorNR3; the or each Y is independently OM, OR3, O(CH2)qSO3l\ / l, NHOH, NHR3, NR32, or X'L, wherein, M is selected from an alkali metal or an alkaline earth metal; the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, a polyoxyalkylene chain having from 2 to 1000 repeating units; q is 1 to 5; and alternatively, NR32 represents a heterocyclic ring; and when Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (II) having X' as defined above in place of Y. When the FWA or optical brightener is of formula (II): R is H, CHR5R6, R5, R6, an alkylsulphonate, a polyether, an optionally substituted aromatic or heteroaromatic ring, CH2COY or CH(COY)((CH)nCOY) in which each Y is the same or different; the or each Y is independently OM, OR3, O(CH2)qSO3M, NHOH, NHR3, NR32, or X'L, wherein, M is selected from an alkali metal or an alkaline earth metal; the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units; q is 1 to 5; and alternatively, NR32 represents a heterocyclic ring; and when Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (II) having X' as defined above in place of Y; and R5 and R6 independently represent hydrogen, alkyl, vinyl, phenyl, hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl, aminomethyl, l-(dimethylamino)methyl, 5-aminopentyl, or cyano, optionally wherein R4 and R5 are the same or different, and n is 1 or 2. By "aromatic" compound, we mean a compound of the class of cyclic (ring-shaped) organic molecules characterised by a specific arrangement of alternating single and double bonds within the ring, leading to a stable, planar structure, and with a "delocalised" n-electron system, where electrons are not confined to specific bonds but rather spread out over the entire ring, contributing to the compound's stability through conjugation. These compounds typically comprise an aryl group. An aryl group is a monocyclic or polycyclic ring system having from 5 to 20 carbon atoms. The aryl group is preferably a "Cg-i2 aryl group" and is an aryl group constituted by 6, 7, 8, 9, 10,11 or 12 carbon atoms and includes condensed ring groups such as monocyclic ring group, or bicyclic ring group and the like. Specifically, examples of "C6-io aryl group" include phenyl group, biphenyl group, indenyl group, naphthyl group or azulenyl group and the like. It should be noted that condensed rings such as indan and tetrahydro naphthalene are also included in the aryl group. By "heteroaromatic" compound, we mean an aromatic compound which contains heteroatoms (e.g. O, N, S) as part of the cyclic conjugated n-system. These compounds typically comprise a heteroaryl group. A heteroaryl group is an aryl group having, in addition to carbon atoms, from one to four ring heteroatoms which are preferably selected from O, S, N, P and Si. A heteroaryl group preferably has from 5 to 20, more preferably from 5 to 14 ring atoms. Specifically, examples of a heteroaryl group include pyridine, imidazole, methylimidazole and dimethylaminopyridine. By "optionally substituted," we mean that a compound which can be substituted may be optionally substituted; that is, we do not mean that only the first species mentioned in the list may be optionally substituted. The term optionally substituted when used herein means unsubstituted or substituted with a suitable group. Suitable groups will be known to the skilled person. Generally, such groups would not significantly detrimentally affect the function of the substituted group or of a larger moiety to which the substituted group is attached. In some cases, the skilled person would expect the substituent to improve the function of the substituted group. As used herein, the term "alkali metal" refers to a Group 1 metal, which may be selected from lithium (K), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), or francium (Fr). As used herein, the term "alkaline earth metal" refers to a Group 2 metal, which may be selected from beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), or radium (Ra). As used herein, the term "alkyl" refers to a linear or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing no unsaturation, and having the specified number of carbon atoms, which is attached to the rest of the molecule by a single bond. In embodiments of the invention, an alkyl group is preferably a "C1-34 alkyl group", that is an alkyl group that is a linear or branched chain with 1 to 34 carbons. The alkyl group therefore has 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, T1, 28, 29, 30, 31, 32, 33, or 34 carbon atoms. Preferably, when a linear alkyl, it is a C7-C34 alkyl, a C8-C34 alkyl, or a C9-C34 alkyl, and when a branched alkyl, it is a C1-C34 alkyl. Specifically, examples of "C1-34 alkyl group" include, but are not limited to, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, l-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, 1-ethylbutyl group, 1-methylbutyl group, 2-methylbutyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, 2-ethylbutyl group, 2-methylpentyl group, 3-methylpentyl group, 3,5-dimethylhexyl group, 2-ethylhexyl group, 8-methylnonyl group, 4-methyldecyl group, 2,4,7-trimethyloctyl group, 4,6-dimethylnonyl group, and the like. As used herein, the term "alkenyl" refers to a linear or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing one or more carbon-carbon double bonds, and having the specified number of carbon atoms, which is attached to the rest of the molecule by a single bond. Alkenyl groups are preferably "C2-30 alkenyl", more preferably "C2-20 alkenyl", even more preferably "C2-15 alkenyl", even more preferably "C2-10 alkenyl", even more preferably "C2-8 alkenyl", most preferably "C2-6alkenyl" groups, respectively. As used herein, the term "alicyclic" refers to a saturated or partially unsaturated cyclic aliphatic monocyclic or polycyclic (including fused, bridging and spiro-fused) ring system which has from 3 to 20 carbon atoms, that is an alicyclic group with 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Preferably, an alicyclic group has from 3 to 15, more preferably from 3 to 12, even more preferably from 3 to 10, even more preferably from 3 to 8 carbon atoms, even more preferably from 3 to 6 carbons atoms. The term "alicyclic" encompasses cycloalkyl, cycloalkenyl and cycloalkynyl groups. It will be appreciated that the alicyclic group may comprise an alicyclic ring bearing one or more linking or non-linking alkyl substituents, such as -CH2-cyclohexyl. Specifically, examples of the C3-20cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl and cyclooctyl. As used herein, the term "heterocyclic" refers to an alicyclic group as defined above which has, in addition to carbon atoms, one or more ring heteroatoms, which are preferably selected from O, S, N, P and Si. Heteroalicyclic groups preferably contain from one to four heteroatoms, which may be the same or different. Heteroalicyclic groups preferably contain from 5 to 20 atoms, more preferably from 5 to 14 atoms, even more preferably from 5 to 12 atoms. Specifically, an example of a heterocyclic group is a morpholine or piperidine group. As used herein, the term "aryl" refers to a monocyclic or polycyclic ring system having from 5 to 20 carbon atoms. An aryl group is preferably a "C6-i2 aryl group" and is an aryl group constituted by 6, 7, 8, 9,10, 11 or 12 carbon atoms and includes condensed ring groups such as monocyclic ring group, or bicyclic ring group and the like. Specifically, examples of "Cb-io aryl group" include phenyl group, biphenyl group, indenyl group, naphthyl group or azulenyl group and the like. It should be noted that condensed rings such as indan and tetrahydro naphthalene are also included in the aryl group. As used herein, the term "alkaryl" (or "alkylaryl") refers to an aryl group as defined above bonded at any position to an alkyl group as defined above. The point of attachment of the alkylaryl group to a molecule may be via the alkyl portion and thus, preferably, the alkylaryl group is -CH2-Ph or -CH2CH2-Ph. An alkylaryl group can also be referred to as "aralkyl." As used herein, the term "alkyl amine" refers to an alkyl group as defined above bonded at any position to an amine group. Specifically, examples of "alkyl amine" include, but are not limited to, aminomethyl, l-(dimethylamino)methyl, 2-(dimethylamino)ethyl, or 5-aminopentyl. As used herein, the term "alkyl alcohol" refers to refers to an alkyl group as defined above bonded at any position to a hydroxyl group. As used herein, the term "alcohol polyol" refers to an organic group, such as an alkyl or alkenyl as defined above, containing multiple hydroxyl groups, for example, at least two, at least three, at least four, or at least five hydroxyl groups. As used herein, the term "alkyl ether" refers to an -O-alkyl group or -alkyl-O-alkyl group, where alkyl is as defined above. As used herein, the term "polyether" refers to a group comprising repeating chemical units linked together by ether groups (C-O-C). As used herein, the term "polyester" refers to a group comprising repeating chemical units linked together by ester groups (C(O)-O-C). As used herein, the term "sugar" refers to a chemical carbohydrate group, which comprises monosaccharides (such as glucose), and complex sugars (such as di-saccharides and poly-saccharides). The general formula of simple sugars is CnH2nOn, where n is typically between 3 and 7, for example glucose, whose formula is CgH^Og. As used herein, the term "polyoxyalkylene" refers to a polymer chain composed of repeating oxyalkylene (ether) units. Each of the alkylene units may be as defined above. The polyoxyalkylenes may be terminated with a hydrogen, a hydroxyl, an alkyl, an alkoxy, or an alkenyl group as described above. For example, when terminated by a hydroxyl, the polyoxyalkylene may by selected from polyethylene glycol (PEG), polypropylene glycol, and the like. As used herein, the term "PEG" refers to polyethylene glycol, a polymer formed of repeating units of ethylene glycol. The structure of PEG is commonly expressed as -(O-CH2-CH2)n-OH, where n is the number of repeating units. PEG groups can vary in size and molecular weight, resulting in different physical properties. For example, when terminated by an alkoxy group, the polyoxyalkylene may by selected from methyloxy-polyethylene glycol (MeO-PEG), ethoxy-polyethylene glycol (EtO-PEG), and the like. As used herein, the term "MeO-PEG" refers to a polyethylene glycol that is terminated with a methyl group. The structure of MeO-PEG is expressed as H-(O-CH2-CH2)n-OMe, where n is the number of repeating units. In embodiments of the invention, the compound may be a betaine. As used herein, the term "betaine" refers to a compound with a positively charged cationic functional group that bears no hydrogen atom, such as a quaternary ammonium or phosphonium cation (generally: onium ions), and with a negatively charged functional group, such as a carboxylate group that may not be adjacent to the cationic site. Thus, in embodiments of the invention when the compound is a betaine, any basic group, such as an amine, may be protonated as a quaternary ammonium cation, and any acidic group, such as a hydroxyl, may be deprotonated as an oxide. The side groups may be selected to compatibilise the FWA or optical brighteners for a target formulation. The core is the component that predominantly provides the fluorescence properties, and the side groups, which may be saturated (i.e. comprise no double bonds) or unsaturated (i.e. comprise double bonds), or linear or branched, are selected to compatibilise the compound with a particular formulation and / or application. Particular embodiments of the FWAs or optical brighteners will now be described. In embodiments when R3 is alkyl, it may be a linear or branched alkyl. In embodiments when R3 represents a linear or branched alkyl, R3 is preferably selected from, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, 1,1-dimethylpropyl, 1,3,3-trimethylpropyl, 2,5-dimethylhexyl, isopropyl, 3-methylpentan-2-yl, 3-methylpentan-3-yl, or tert-butyl. In some particular embodiments R3 may be a Ci-C34 alkyl. In embodiments when R3 is a polyoxyalkylene, it may be selected from PEG or MeO-PEG. In embodiments where R3 is PEG, it may have having from 2 to 1000 repeat units. More preferably, it has 2 to 20 repeat units. Still more preferably, it has 8 to 12 repeat units. Most preferably, it has 3 repeat units. In embodiments were R3 is MeO-PEG, it may have having from 2 to 1000 repeat units. More preferably, it has 2 to 20 repeat units. Still more preferably, it has 8 to 12 repeat units. Most preferably, it has 3 repeat units. In embodiments where R3 is a linear or branched polyether, it may be preferably selected from polycitronellols, or polycitronellol derivatives, such as isocitronellol. In embodiments where R3 is a branched alkyl alcohol polyol, it may be preferably selected from polyglycerol, polyglycerol derivatives. Each instance of R3 may be the same as, or different to, each other. Advantageously, this means that the compound may be balanced with respect to its compatibility with the formulation or composition, which enables enhancement of the composition for a particular personal care product. 5 In particular embodiments, such as formula (Ic), wherein A is an optionally substituted aromatic or heteroaromatic ring fused with N and X, the substituted aromatic or heteroaromatic ring may be substituted by at least one R1, at least two R1, at least three R1, or at least four R1. The or each R1 may be independently H or -C(O)ZR3, as previously defined. 10 In exemplary embodiments, the FWA or optical brightener compounds may be selected from: 6 7 8 In further exemplary embodiments, the FWA or optical brightener compounds may be selected from: 15 In some embodiments of the invention, Y may be X'L. In such embodiments, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (I) or (II). In such cases, the FWA or optical brightener may have the formula W-X'-L-(X'-W)m, wherein W is a FWA of formula (I) or (II) connected to m repeating units of formula (I) or (II) by linker L, wherein m is 1 or more. In such embodiments, m may be 1 or more, 2 or more, 3 or more, or 4 or more. In such embodiments, m may be 1 to 20, 2 to 20, 2 to 15, or 5 to 10. In such embodiments W may be the same or different FWA compound. Linker L may be constituted by any of alkylene, a polyol, an amine, a polyester, a polyoxyalkylene, triethanolamine, glycerol, a sugar, a carbohydrate, or derivatives thereof. For example, in embodiments when the linker L is a sugar, or a sugar derivative, it may be selected from sucrose, glucose, sorbitol, sorbitan, and the like. For further example, in embodiments when the linker L is a carbohydrate, it may be a polysaccharide. Advantageously, linkers such as those described above, offer unique advantages in personal care applications, primarily due to their biocompatibility, which minimises toxicity. Additionally, they are typically derived from natural sources and can be chemically modified to tailor the compound to a range of applications. Sugar-based linkers also often increase water solubility of the overall structure. In embodiments where the linker L is a polyester or a polyoxyalkylene, it may have from about 2 to about 1000 repeating units, from about 2 to about 30 repeating units, or from about 8 to about 20 repeating units. In particular embodiments, linker L may be derived from a polyol, in which case X' is the oxygen of the precursor alcohol; or the linker may be derived from an amine, in which case X' is the nitrogen of the precursor amine. In specific embodiments of the invention, the linker may be able to support multiple FWA compounds, examples of such linkers are given below, which may be combined in each position with compounds according to: (I) In embodiments where the linker L has multiple sites to which a FWA compound of formula (I) or (II) may be linked, the FWA compounds may occupy any site, and the remaining sites may be 5 functionalised with hydrogen (i.e. as an OH), an alkyl (i.e. as an OR), or a polyoxyalkylene (such as, PEG, for example). In specific embodiments where Y is X'L, the FWA or optical brightener compounds may be selected from, any of the following: 10 5 In embodiments according to the invention, the FWA or optical brightener, and compositions and formulations thereof, may be used in personal care or a personal care product. Typically, the use may be selected from haircare, skincare, dental care, or UV-protection. Examples products associated with these uses may include shampoos, conditioners, toothpastes, sunscreens, skin creams, eye creams, dental products, nail varnishes, wax-based products, and the like. 10 In dental care applications, the fluorescent whitening agent or optical brightener composition may be used for whitening and antimicrobial treatment of dental care products, denture care and oral care products, such as tooth paste, tooth cream, tooth gel, tooth powder, mouthwash concentrate, antiplaque mouthwashes, dental prosthesis cleaners or dental prosthesis adhesives. Advantageously, in some dental care applications the FWA or optical brightener is able to act in a multifunctional manner. For example, in toothpaste, the FWA or optical brightener is able to enhance whitening effect of teeth to provide instant whiter teeth, as well as contributing to antibacterial effect of toothpaste. In haircare or skincare applications, the fluorescent whitening agent or optical brightener composition may be used for whitening or brightening of the skin, and / or hair, as well as contributing to antimicrobial effects which could be used in cosmetic or personal care products to help with treatment, de-odorisation through microbial disruption, or preservation. Haircare or skincare products may be, for example, make-up, eye creams, lip care products, nailcare products, footcare products, sunscreens, skin-tanning preparations, depigmentation products, insect-repelling products, deodorants, hair-removal products, shaving products, fragrances, shampoos, conditioners, haircare products, or skin cleaning products such as soap and body wash. In some skincare embodiments, the FWAs or optical brighteners may be employed in a non-colour cosmetic but one that gives a brightening effect, this could be in the form of a transparent or translucent product, or another suitable type of skin treatment product. In such a skincare product, the FWA or optical brightener may be used alone as the primary component, for the purpose of evening or brightening skin tone, to disguise dark shadows, undereye circles, lines, and wrinkles on the skin, or to counteract the effects of reddening from rosacea, for example. Alternatively, they may be used in combination with additional skin care treatment actives for a range of personal care products, such as, but not limited to, those that improve or eradicate age spots, keratoses and wrinkles, analgesics, anaesthetics, anti-acne agents, anti-bacterials, anti-yeast agents, anti-fungal agents, anti-viral agents, anti-dandruff agents, anti-dermatitic agents, anti-pruritic agents, anti-emetics, animation sickness agents, anti-inflammatory agents, anti-hyperkeratolytic agents, antidry skin agents, anti-perspirants, anti-psoriatic agents, anti-seborrheic agents, anti-aging agents, antiwrinkle agents, anti-asthmatic agents and bronchodilators, sunscreen agents, anti-histamine agents, skin lightening agents, depigmenting agents, wound-healing agents, vitamins, corticosteroids, self-tanning agents, or hormones. In UV protection applications, the FWA or optical brightener may be used to help decrease the use of physical UV filters, such as TiOj, or in synergy with said filters to increase the UV absorption efficiency. In wax-based product applications, the FWA or optical brightener may be used in, but not limited to, candles, lipsticks, depilatory (hair removal) wax, or crayons. The wax may be selected from any suitable wax, such as for example a natural wax, mineral wax, or a synthetic wax. In embodiments where the wax is a natural wax it may be selected from, for example, beeswax, lanolin, shellac, carnauba wax, candelilla wax, soy wax, palm wax, and the like. In embodiments where the wax is a mineral wax, it may be selected from, for example, paraffin wax, or microcrystalline wax. Additionally in some embodiments of the invention, the FWAs or optical brighteners may act as a preservative, or a preservative booster. Particularly the FWAs or optical brighteners may extend the lifetime of the formulation or composition in which they are comprised. Advantageously, the UV absorbance properties of the FWAs or optical brighteners of the present invention affords protection to the personal care products, particularly to high value personal care products left on the shelf in light environments, such as perfumes and aftershaves. The FWAs or optical brighteners achieve this by absorbing damaging radiation. In embodiments of the invention, the amount of FWA or optical brightener to be used in any given formulation may be readily determined in accordance with the usual dosage. The amount of FWA or optical brightener may be varied depending upon the intensity of the fluorescence or UV absorbance and the desired effect, and can be up to about 50 wt.%, up to about 25 wt.%, up to about 20 wt.%, up to about 15 wt.%, up to about 10 wt.%, up to about 5 wt.%, or up to about 2 wt.%. In particular embodiments, the FWA or optical brightener may be present in the formulations or compositions from about 0 to about 15 wt.%, preferably from about 0 to about 10 wt.%, more preferably from about 0 to about 5 wt.%, and most preferably from about 0 to about 2 wt.%. In embodiments of the invention, the mode of application of the formulations or compositions of the invention will depend upon the final intended use. For example, in a colour cosmetic or makeup product, the formulation or composition will normally be applied on an as-needed basis, to the face, or optionally the body, for example as part of the user's daily makeup routine. In a non-colour cosmetic or other skincare treatment product, the composition can be applied daily, with or without makeup, simply to replenish the skin's natural glow and to cause unadorned skin to appear healthier and younger. It may also be applied to particular trouble spots, such as dark undereye shadows, in order to brighten their appearance. In some embodiments of the invention, the FWA or optical brightener may improve the appearance of a personal care product, for example, by making the product whiter. In some embodiments of the invention, the FWA or optical brightener may improve the effect of the personal care product, for example, whiter teeth, shinier hair, brighter skin, and the like. Thus, the FWA or optical brightener may enhance appearance. The appearance enhancing characteristics of the FWA, or optical brightener may depend on the control of specular versus diffuse reflectance in the formulations or composition. For example, gloss, i.e. a high specular reflectivity is usually undesirable in most face powders and the like where a matte or flat finish may be desirable. In contrast, for hair care formulations, lipsticks, nail enamels, and the like it is frequently desirable to increase gloss, i.e. the ratio of specular to diffuse reflectance. This diffuse reflectance can have some desirable effect in skin formulations, to either blur out blemishes, wrinkles, and fine lines via products such as foundation make-up, under-eye cream or serum, or to impart a general lustre, luminosity, radiance, glow or sheen to the skin via products such as face or skin cream, or dewy powders. In particular instances, the incorporation of the FWAs or optical brighteners in formulations or compositions for personal care use may have the effect of enhancing the lustre, shine, or colour intensity of the composition. In some embodiments, the FWAs or optical brighteners according to the invention may be antimicrobials. Advantageously, the compounds may exhibit an antimicrobial effect against pathogenic bacteria. They are therefore suitable, in particular, for the disinfection, deodorisation, and also the general and antimicrobial treatment of the skin and mucosae, and skin appendages, such as hair. They are therefore also suitable as antimicrobial active substances and as preservatives or preservative boosters in personal care compositions, such as, for example, shampoos, tooth paste, bath products, haircare compositions, liquid and solid soaps (based on synthetic surfactants and salts of saturated and / or unsaturated fatty acids), lotions and creams, deodorants, other aqueous or alcoholic solutions, e.g. cleansing solutions for the skin, moist cleansing wipes, oils or powders. In some embodiments, the FWA or optical brightener may be formulated in combination with further adjuvants, additives, and / or components to alter and / or control the properties of the formulation or composition. The present invention therefore provides a fluorescent whitening agent or optical brightener composition for use in personal care, comprising at least one fluorescent whitening agent or optical brightener and cosmetically acceptable carriers or auxiliaries. The formulations or compositions may additionally comprise colorants, fragrances, emollients, surfactants, humectants, thickeners, stabilisers, preservatives, pH adjusters and pH buffers, UV-absorbers, silicones, chelating agents, film-forming agents, natural extracts, antioxidants, disinfectants, and / or antimicrobials. Personal care products can come in different physical forms such as liquid solutions, solid bars, and sticks, semi-solid or emulsion-based mixtures, powders, aerosols, oils, gels, scrubs, and sheets. Therefore, the FWAs or optical brighteners may be incorporated into any kind of vehicle that is normally used for personal care compositions, such as, but not limited to, solutions, colloidal dispersions, emulsions (oil-in-water or water-in-oil), suspensions, powders, which may be sold as creams, lotions, gels, foams, mousses, sprays, etc. Methodology for formulation of different vehicle types is well known in the art and can be found for example in Remington's The Science and Practice of Pharmacy, 19th Edition, Volume II. Examples of solvents that are suitable not only as carriers for cosmetics but also as carriers for the FWAs or optical brighteners are, but not limited to, acetic acid, n-butanol, alkyl methicones, cyclohexane, cyclomethicone, diethylene glycol, triethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutylether, butylene glycol, glycerine, polysorbates, propylene glycol, dimethicone, dimethiconol, dipropylene glycol, 95 % ethanol, ethoxy diglycol, ethoxyethanol, dimethyl isosorbide, ethyl acetate, butyl acetate, dimethyl capramide, isododecane, 0.1N hydrochloric acid, isopropanol, methyl ethyl ketone, phenyltrimethicone, polycitronellol, mineral or vegetable oils, water and mixtures thereof. Additional solvents suitable for use with the formulation or compositions of the present invention are listed in the International Cosmetic Ingredient Dictionary, Fifth Edition, Edited by John A. Wenninger and G. N. McEwen, Jr., and published by the Cosmetic Toiletry and Fragrance Association, Washing ton D. C. (1993). In particular embodiments, the FWAs or optical brightener compositions may be formulated as a water-in-oil emulsion or oil-in-water emulsion, as an alcoholic or alcohol-containing formulation, as a vesicular dispersion of an ionic or non-ionic amphiphilic lipid, as a gel, solid stick or as an aerosol formulation. As a water-in-oil or oil-in-water emulsion, the carrier preferably comprises from about 5 to about 50% of an oil phase, from about 5 to about 20% of an emulsifier and from about 30 to about 90% of water. The oil phase can comprise any oil suitable for cosmetic formulations, such as, for example, one or more hydrocarbon oils, a wax, a natural oil, a silicone oil, a fatty acid ester or a fatty alcohol. Preferred mono- or polyols are ethanol, isopropanol, propylene glycol, hexylene glycol, glycerol, and sorbitol. In a particular embodiment, the formulation or composition is for use in dental care as an oral composition, for example, in the form of a gel, a paste, a cream or an aqueous preparation (mouthwash). In said embodiment the oral composition may further comprise compounds which release fluoride ions, which are effective against the formation of caries, e.g. inorganic fluoride salts, such as, for example, sodium fluoride, potassium fluoride, ammonium fluoride or calcium fluoride, or organic fluoride salts. For example, an antimicrobial, whitening soap may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 0.3 to 1% by weight of titanium dioxide; 1 to 10% by weight of stearic acid; 0.1 to 2.0% fragrance or essential oil blend; and balanced to 100% of soap base, such as, for example, the sodium salts of tallow fatty acid and coconut fatty acid, palm fatty acids, or glycerol. For example, a body skin cream may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 15 to 20% by weight of coco-caprylate; 0.5 to 5% by weight of polyglycerin; 1 to 3% by weight of glyceryl stearate; 0.5 to 3% by weight of starch; 1 to 2% by weight of cetearyl alcohol; 0.5 to 2% by weight of xanthan gum cellulose; 0.5 to 1.5% by weight of a preservative; 0.1 to 1.5% fragrance or essential oil blend; and balanced to 100% with water, and pH adjusted with citric acid or sodium hydroxide. For example, a face cream may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 5 to 10% by weight of clO-18 triglycerides; 2 to 4% by weight of glycerin; 5 to 8% by weight of octyldodecyl myristate; 4 to 7% by weight of shea butter ethyl ester; 1 to 3% by weight of polyglyceryl-6 distearate; 1 to 3% by weight of polyglyceryl-3 oleate; 1 to 2% by weight of starch acetate; 0.5 to 1% by weight of hydroxyethyl cellulose; 0.1 to 1% by weight of xanthan gum; 0.5 to 1.5% preservative; 0.1 to 1.0% fragrance or essential oil blend; and balanced to 100% with water. For example, a shampoo may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 1-5% by weight sodium lauroyl sarcosinate 0.5 to 1.5% by weight cocamidopropylbetaine 0.1 to 2.0% by weight polyquaternium-7 0.1 to 1.0% by weight carbomer 0.5 to 2.0% by weight preservative 0.1 to 2.0% fragrance of essential oil blend; and balanced to 100% of water, and pH adjusted with sodium hydroxide. For example, a conditioning shampoo (two in one) may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 1-5% by weight sodium lauroyl sarcosinate; 4.0% 0.5 to 1.5% by weight of cocamidopropylbetaine; 0.1 to 2.0% by weight polyquaternium-7 5 0.1 to 1.0% panthenol 0.1 to 1.0% argan oil 0.1 to 1.0% by weight carbomer 0.5 to 2.0% by weight preservative 0.1 to 2.0% fragrance or essential oil blend; and 10 balanced to 100% of water, and pH adjusted with sodium hydroxide. For example, a deodorant may have the following composition: 0.01 to 5% by weight of the FWA or optical brightener compound; 0.5 to 5.0% by weight propylene glycol; 15 40 to 70% by weight of ethanol; 40 to 80% by weight of butanol; 0.5 to 2.0% by weight of perfume oil; and balanced to 100 % of water. 20 For example, an oral composition (e.g. toothpaste) may have the following composition: 0.1 to 0.5% by weight of the FWA or optical brightener compound; 10 to 40% by weight of sorbitol; 5 to 20% by weight of glycerol; 0.5 to 1.5% by weight of sodium lauryl sulphate; 25 0.1 to 0.25% by weight of sodium methyl cocyltaurate; 0.25% by weight of polyoxypropylene / polyoxyethylene block copolymer; 0.10 to 1.5% by weight of flavouring; 0.1 to 0.5% by weight preservative; and balanced to 100 % of water. 30 Due to performance, health, and environmental concerns, fewer than 50 FWAs or optical brighteners are still in mass production for commercial uses. Those remaining have acceptable safety profiles in terms of their toxicity to the environment and human health. However, they remain of concern due to a variety of factors, including a lack of biodegradability, reproductive toxicity concerns, and potential irritation to sensitive skin. Biodegradability remains one of the most significant areas of concern as once discharged as wastewater, the FWAs or optical brighteners are released from water treatment plants into open or underground water. The industry standards frequently biodegrade slowly and may end up accumulating in the marine ecosystem, as well as being acutely harmful to aquatic organisms. The FWAs or optical brighteners, and compositions and formulations thereof, are derived from naturally derivable cores, such as citric acid and are therefore advantageously biodegradable. Advantageously, the FWAs and optical brighteners contained within the formulations or compositions in accordance with the invention are biodegradable. Preferably they contain at least one functional group which is not oxidised, or which is only partially oxidised, and thereby is oxidisable or further oxidisable. Preferably they contain at least one hydrolysable group. Therefore, the FWA or optical brightener may comprise at least one labile group. Inherently biodegradable fluorescent whitening agents may be defined as >20% but <60% biodegradability in water as measured by standard OECD 301A-F testing. A readily biodegradable fluorescent whitening agent or optical brightener may be characterised by the ability of the material to biodegrade quickly and completely in water (either >70% dissolved organic carbon removal, >60% theoretical carbon dioxide or >60% theoretical oxygen demand, depending on standard OECD 301A-F test methods) in a 10-day window within 28 days. Synthesis of Fluorescent Whitening Agents The FWAs and optical brighteners in accordance with the invention may be synthesised from readily available and bio-renewable starting materials, such as for example, citrazinic acid or citric acid. In some embodiments, the method of synthesis may be water-based or use green chemistry methods. As used herein, the term "bio-renewable" refers to materials and resources derived from natural sources, such as plants or animals, i.e. recently living organisms (biomass), that can be replenished at a rate that makes them available for future use. Examples of bio-renewable materials include, but are not limited to, algae, sugars, starches, corns, natural fibres, sugarcanes, beets, citrus fruits, woody plants, cellulosics, lignocelluosics, hemicelluloses, potatoes, plant oils, other polysaccharides such as pectin, chitin, levan, and pullulan, and a combination thereof. As used herein, the term "green chemistry" means the design of products and associated processes that reduce or eliminate the use of hazardous substances throughout the entire life cycle of a chemical product. The approach aims to prevent pollution at its source by developing chemicals and processes that are inherently safer for human health and the environment, promoting efficiency in resource and energy use. A general synthesis of the compounds of structure (I) from citric acid is shown below in Scheme 1, where X, A, and Y are as defined above. Scheme 1 As detailed above, in exemplary embodiments of structure (I), the compounds may be selected from, any one of, formula (la), formula (lb) or formula (Ic). A general synthesis for these compounds is shown below in Scheme 2, where Ri, R3, X and Z are as defined above: Esterification or Amidation Scheme 2 A general synthesis of the compounds of structure (II) from citrazinic acid is shown below in Scheme 5 3, where R, and Y are as defined above. 10 As shown above, the compounds may be synthesised by conventional methods such as heating citric acid with a second amine building block in the presence of water, with water itself as the major byproduct. Advantageously, water-based synthesis is safer, cleaner, more environmentally friendly, and highly scalable industrially. The skilled person would be able to readily adapt the above to access a range of chemical structures in accordance with structure (I) and (II). Further synthetic functionalisation of the core units to modify and / or improve substantivity of the resultant FWA or optical brightener compound in the desired formulation or composition or desired personal care application may be readily achieved by a second, facile reaction with either an alcohol or amine. Suitable groups will be known to the skilled person. Generally, such groups would not significantly detrimentally affect the function of the substituted group or of a larger moiety to which the substituted group is attached. In some cases, the skilled person would expect the substituent to improve the function of the substituted group. In particularly advantageous embodiments, the other reagents, such as the alcohol and amine can also be bio-derived or bio-renewable. For example, they may be derived from fatty alcohols. Advantageously, the synthesis of the compounds is highly tuneable, and enables easy alteration of the side groups, increasing the adaptability of compounds to different personal care applications by matching the side groups accordingly. The invention will now be more particularly described with reference to the figures and drawings in which: Figure 1 shows a graph of the UV absorption for three different FWA candidates according to the invention. Figure 2 shows an image that illustrates the foaming properties of FWA candidates according to the invention. Referring to Figure 1, there is shown a graph of the UV absorbance for three of the FWA or optical brightener molecules according to the invention, measured at a concentration of 0.1 mg / ml in water. EXAMPLES EXAMPLE 1: Synthesis of FWA Compounds Synthesis of Fluorescent Whitening Agent Core Units from Citric Acid with Structure I A mixture of citric acid (1 e.q.) and corresponding amine (1 e.q.) were dissolved / suspended in water (1 vol.). Water is then removed from the mixture under reduced pressure to give a pre-reaction residue. For FWA cores with a melting point <140°C, the residues are heated to 140°C with stirring and the water of reaction is allowed to distil for 16h. The resulting residue is then cooled to room temperature and slurried in fresh water (0.5 vol.). The desired product is then isolated by filtration, washed with water (0.25 vol.), and dried in a vacuum oven. For FWA cores with a melting point >140°C the initial residues are first suspended in mixed xylenes (3 vol.) before refluxing for 16h. The reaction is then cooled to room temperature and the xylenes decanted to waste before the resulting is slurried in fresh water (0.5 vol.). The desired product is then isolated by filtration, washed with water (0.25 vol.), and dried in a vacuum oven. Synthesis of Fluorescent Whitening Agent Core 1 In a representative reaction, a mixture of citric acid (384.2g, 2mol) and cysteine (242.2g, 2mol) were dissolved in water (600ml). Following removal of water under reduced pressure, the resulting white residue was heated to 130°C with an anchor stirrer to ensure efficient mixing. The reaction mixture was heated to 100°C to allow all water to distil. The molten mixture was then stirred for 2.5h and the water of reaction allowed to distil. The resulting resinous material was cooled <100°C before adding fresh water (620ml) to slurry the product. The mixture was then cooled to ambient temperature with vigorous stirring to disperse the product before filtration. The isolated solids were washed with fresh water (300ml) before drying in a vacuum oven to give the final product as a yellow powder in 85% yield (412.5g, 1.7mol). Analytical Data: HPLC purity: 99.8%; LCMS (+ve ion): m / z 242.2; 2H NMR (DMSO-d6, 400 = MHz, d): 6.59 (s, 1H), 6.52 (s, 1H), 5.46 (d, 1H), 3.92 (t, 1H), 3.60 ppm (d, lH^C^H) NMR (DMSO-d6, 75MHz, d): 169.2, 165.6, 160.7, 150.2, 142.7, 114.8, 97.9, 62.6 ppm. Esterification of Fluorescent Whitening Agent Core Unit with High-Boiling Alcohols (>100°C) A mixture of prepared FWA core (1 e.q.) was suspended in alcohol (1.1 e.q. per carboxylic acid group) with p-toluenesulphonic acid (0.08 e.q.). The resulting mixture was then heated to >100°C, with 130°C being the preferential reaction temperature, and the water of reaction allowed to distil over 16h. The excess alcohol was then removed under reduced pressure or azeotropic distillation where appropriate. For alcohols with high boiling points and no azeotrope the desired esters were purified either by column chromatography or by precipitation from acetone. Esterification of Fluorescent Whitening Agent Core Units with Low-Boiling Alcohols (<100°C) A mixture of prepared FWA core (1 e.q.) was suspended in alcohol (3 vol.) and heated to reflux before stirring for 24h. The reaction was then allowed to boil dry to remove the water of reaction. Fresh alcohol (3 vol.) was then added to reaction and the reflux continued for a further 24h. The reaction mixture was then cooled, and the solvent removed at reduced pressure to give the target ester in near quantitative yield. Amidation of Functionalised Fluorescent Whitening Agents In a typical procedure, a mixture of FWA core (1 e.q.) and desired amine side chain (2 e.q. per acid group) were heated to 130°C under a blanket of nitrogen. Once at temperature, the water of reaction was allowed to distil until such a time no further distillation was observed. Completion of reaction was confirmed by HPLC, before cooling the reaction to room temperature. Crude mixtures were then diluted with IM NaOH and extracted with DCM (3 x 20 vol.). The solvent was then removed under reduced pressure to give the desired product. Purification was achieved either by column chromatography or recrystallisation from MTBE / Ethanol (1:1) where appropriate. Amidation of Fluorescent Whitening Agent Core with a Peptide Coupling Catalyst In a representative example, FWA core (1 e.q.) was dissolved in DCM (10 vol) with triethylamine (2 e.q. per acid group) and the desired amine (1.05 e.q. per acid group). Propanephosphonic acid anhydride (T3P, 50% in THF 1.5 e.q. per acid group) was then added to the mixture before stirring at ambient temperature for 16h. Where the desired amide precipitated from the reaction mixture, solids were isolated by filtration and dried in a vacuum oven to give the isolated product without further purification. Where the amide product did not precipitate, the reaction mixture was washed with IM NaOH (10 vol.) before concentrating the organic phase under reduced pressure. Purification of the crude products was then achieved by column chromatography, or crystallisation from MTBE / EtOH, where appropriate. Synthesis of Fluorescent Whitening Agent Core Units from Citric Acid with Structure II A mixture of desired amine compound (1 e.q.) and citric acid (1.05 e.q.) are stirred under reduced pressure (<100 mbar) before heating to >100°C to melt and the resulting water of reaction allowed to distil. The reaction is monitored by the evolution of water, while modulating the reaction pressure to control foaming. Once no further distillation is observed, completion is confirmed by HPLC analysis. Sulphuric acid is then charged to the mixture and distillation under reduced pressure is continued. Once no further distillation is observed, completion is again confirmed by HPLC before cooling to room temperature. The crude product is then dissolved in organic solvent (3 vol.) and washed with saturated brine (3x1 vol.), before removing the solvent under reduced pressure to give the final product. Example Synthesis of Fluorescent Whitening Agent Core Unit Structure II from Dodecylamine A mixture of dodecylamine (55.6 g, 0.3 mol, 1 e.q.) and citric acid (60.5 g, 0.315 mol, 1.05 e.q.) were processed as per the above procedure to give the final product as a beige wax in 92% yield (89.6 g, 0.277 mol). Analytical Data: HPLCpurity: 97.3%; LCMS (-ve ion): m / z 322.2; }H NMR (DMSO-d6, 700 = MHz, d): 6.49 (s, 1H), 3.34 (m, 2H), 1.50 (m, 2H), 1.23 (m, 20H), 0.85 (s, IHy^CfH} NMR (DMSO-d6, 700MHz, d): 173.93, 171.02, 166.56, 141.17, 120.84, 38.80, 38.22, 31.32, 29.07, 29.02, 28.87, 28.73, 28.55 ppm. Example Synthesis of Fluorescent Whitening Agent Core Unit Structure II from Benzylamine A mixture of benzylamine (32.2 g, 0.3 mol, 1 e.q.) and citric acid (60.5 g, 0.315 mol, 1.05 e.q.) were processed as per the above procedure to give the final product as a light orange-brown powder in 81.7% yield (60.2 g, 0.245 mol). Analytical Data: HPLCpurity: 96.7%; LCMS (-ve ion): m / z 244.1; }H NMR (DMSO-d6, 700 = MHz, d): 7.26 (m, 5H), 6.53 (s, 1H), 4.66 (s, 2H), 3.68 (s, 2H); ^CfH) NMR (DMSO-d6, 700MHz, d): 173.87, 169.15, 165.99, 141.06, 135.86, 128.52, 127.67, 121.34, 41.71, 34.48 ppm. EXAMPLE 2: Relative Quantum Yield of FWA The relative quantum yield of the FWA in solution was calculated against quinine sulphate in 0.5M sulfuric acid (¢=0.55), and is shown in Table 1, with a comparison to the industry standard, DSPB. Compound numbers reference the compounds noted above. 5 Table 1: Fluorescence properties of the FWA core (I) compared to DSPB Structure or Compound Number Excitation, lex(nm) Emission, lem(nm) Relative quantum yield, (¢) Benchmark (DSPE CAS 27344-41-8 J) 350 429 0.78 HO^.0 JUL O^N^s 0^ / OH Compound 1 350 418 0.72 ho^o Xl 0 NO Compound 2 344 418 0.61 HO^O JUL O^N^o H0^—1 %H Compound 3 329 411 0.47 HO^O Compound 4 350 452 0.19 ho^° Xi O^N^nh 0 Compound 5 383 453 0.20 HO^O JU O^"N N" 0 Compound 6 384 430 0.28 HO^O HO^O Jul JUl o N hIH 0 N fc|H OH HO Compound 7 315 484 0.14 Jul O^nUh Compound 10a 350 453 0.15 EXAMPLE 3: Modulation of FWAs Through Changes in Side Chains Emission of blue light via fluorescence for optical brighteners based on formula (I) is the results of the 5 n*- n transitions of the carbon-oxygen double bond, found in the pyridone scaffolds based on pyridone. The carboxyl groups of the described FWA cores are believed to have a minimal contribution to this system, it is therefore possible to modify the structure of the described FWAs with minimal impact on the fluorescent behaviour. 10 Table 2: Comparison of varying core side chains, highlighting the minimal changes in fluorescence emission wavelength within the desired blue range of 420 - 470nm Structure Emission lem at lex 350nm (nm) HO^O Jul 418 o / z—Z o 431 0 s—' 431 0 S—' 433 zz 422 O o=\ zz 421 / o o o ^=° «zS / Z—Z ^7 o 433 ^o o^ q HH o o Z o \=o «-0 1 z—Z o 435 ^O O—k p p h n o o ( o o-f) d4 427 p? o z 430 >■? o r 456 Ar w 451 bP p < 428 0 '^^sVf / -Q 439 zz 439 0 "O'y S^Xx?-0 j-b 445 HO ^0 0^ n 'N^S 418 0¾ OH O ^x^O s^N s— / 0 O-\.^ 433 yV S—' p X°^X--\ 431 0 ^X^O ^N s— / p o"X--\ 423 H 0 ^x^O yN s— / 0 N-^\ _ H v— 423 H 0 ^x^O -_Ns S-^ 0 N-"\ H --- 422 0 ^O' ^Nx s— / 0 o-" 434 HO ^° 0^ HO^ ^N^o 419 ^OH 0, ^OH N^ O 435 0% N^ o 439 H 1 1 433 X P Q o 431 cr'N'x) 437 o —Z \ 444 EXAMPLE 4: Modifications FWA Physical Properties Through Side Chain Variation Sensory properties and manufacture processing of different cosmetic products can be influenced by 5 different physical properties such as but not limited to melting point, pouring point, viscosity at certain temperatures, solubility within other cosmetic ingredients. It is therefore advantageous to be able to modify the physical behaviour of FWAs to meet some desired sensory properties and processing conditions. Thermal behaviour of various FWA structures has been assessed by Differential Scanning Calorimetry (DSC), and the results are shown below in Table 3. 10 Table 3: Comparison of Physical Thermal Properties of Different FWA Candidates by DSC Structure Physical Form Melting Point (°C) HO^O fji O^N^s Os / OH Yellow powder 246.3 o r Beige powder 76.0 J cA° Yellowgreen waxy powder 34.4 0 coccoYo Yellow waxy solid 86.1 r ZI L Beige solid 194.3 o^ZT zx Off-white solid 184.7 0 .°^^Aq»0 s^o-'V-o.__ 'b"" Amber oil <20 HO^O fjl Yellow powder 270.5 o r Brown oil <20 o \=o M-o / z—Z o Beige solid 45.7 / q / / \=o / z—Z o Yellow waxy solid 87.1 0 ----“Yr S- / White solid <20 0 ccoXr S— / White solid 108.1 / o o o \=o / z—Z o Yellow oil <20 Q Q HU o o / Yellow oil 88.3 w? o o 0 / Yellow solid 124.3 O^OH Beige wax ~50 (broad) o \ ° \ °z $ / °z ( O \ / Viscous brown oil <20 H °Yn^n" 1 1 Brown gel <20 T z>° O o / —\ / 7 o Orangebrown powder 83.3 o o o / Viscous amber oil <20 H 1 1 O^N^O "o Red-brown gel <20 The results in Tables 2 and 3 highlight that FWAs based on formula (I) can be heavily modified to fit the desired properties in cosmetic formulations or processing, while advantageously having little effect on the desired wavelength of emitted fluorescence. 5 EXAMPLE 5: Biodegradability Assessment Biowin™ software was used to provide predictions of biodegradability. This method of prediction of biodegradability is available as part of the Estimation Program Interface (EPI) Suite™ of software provided by the United States Environmental Protection Agency (EPA). Environ. Sci. Technol., 1994, 28, 459-465, shows an example of the group contribution method for predicting probability and the 5 rate of aerobic biodegradation. This is the type of method used by Biowin™. Biowin 3 and Biowin 5 models are of particular relevance to the present invention. The predicted biodegradability of some of the compounds according to the present invention were assessed using these models. If the Biowin 3 (ultimate survey model) result is >= 2.75 (i.e. "weeks" or faster) and the 10 Biowin 5 (MITI linear model) probability is >= 0.5, then the prediction is YES (readily biodegradable). If this condition is not satisfied, the prediction is NO (not readily biodegradable). The results are provided below in Table 4. Table 4: Biowin predicted biodegradability score Structure or Compound Biowin 3 Biowin 5 Interpretation of Biowin 3 &5 prediction. Benchmark (DSPB) CAS 27344-41-8 0.0223 2.1266 [very poor] Recalcitrant based on Biowin criteria, confirmed experimentally as "neither readily nor inherently biodegradable", see ECHA (https: / / echa.europa.eu / registration-dossier / - / registered-dossier / 14744 / 5 / 3 / l) HO^O xi O^N^s 0=7 OH Compound 1 3.3411 0.528 Readily biodegradable according to Biowin criteria (Biowin 3 >2.75 AND Biowin 5 >0.5). HO^^O °^nX,s Compound 2 3.0738 0.4851 Expected to be biodegradable: Biowin 3 above threshold, Biowin 5 close to it. HO^O Xjl O^N^o ^OH Compound 3 3.0757 0.8247 Readily biodegradable according to Biowin criteria. HO.,0 / a cr n'Jnh Compound 4 3.1359 0.5691 Readily biodegradable according to Biowin criteria. HO^O Xa CT'N nH & Compound 5 2.8703 0.2286 Expected to be moderately biodegradable: Biowin 3 is above threshold, Biowin 5 is significantly better than benchmark. HO^O Xa o^n^n-d Compound 6 2.7195 0.2601 Expected to be moderately biodegradable: Biowin 3 score is within 2.25-2.75 range, Biowin 5 is significantly better than benchmark. HO^O Xa O^N^nh o 0=^ OH Compound 7a 2.8609 0.4664 Expected to be biodegradable: Biowin 3 above threshold, Biowin 5 close to it. HO^O Xa CjN NH HO Compound 7b 2.8609 0.4664 Expected to be biodegradable: Biowin 3 above threshold, Biowin 5 close to it. Xa Compound 9a 2.7757 0.6909 Readily biodegradable according to Biowin criteria. Xa Compound 10a 2.8378 0.7749 Readily biodegradable according to Biowin criteria. Xa 0 Oh Compound 10b 2.7758 0.7902 XI. O^h Compound 10c 2.7138 0.8056 XI o-n-nh Compound lOd 2.6518 0.821 ho^o O^N^O Compound 11a 3.1474 0.5010 Readily biodegradable according to Biowin criteria. O^N^O Compound 12 2.7414 0.3759 Expected to be moderately biodegradable: Biowin 3 score is within 2.25-2.75 range, Biowin 5 is significantly better than benchmark. O^N^O 1 Compound 13 2.4180 0.4898 Expected to be moderately biodegradable: Biowin 3 score is within 2.25-2.75 range, Biowin 5 close to threshold. H kO^N^O ^OH %H Compound 14 2.7630 0.6302 Readily biodegradable according to Biowin criteria. ii \ 4 H ___N N Compound 15 2.5907 0.4369 Expected to be moderately biodegradable: Biowin 3 score is within 2.25-2.75 range, Biowin 5 is significantly better than benchmark. EXAMPLE 6: Evaluation of FWA in Hair A 0.5%w / w solution of each FWA sample was prepared as followed: 0.25g of sample was dispersed in 5 50mL of tap water, when one or more free carboxylic acid is present in the sample structure, the corresponding mole equivalent of Sodium hydroxide was added as a IM solution. It was noted that at this concentration, DSPB remained opalescent. Three different coloured types (dark / mid brown, dark blond natural, light blond bleached) of 5 European hair swatches (1g, 15cm each) were tested. Each hair swatch was added to a test tube, then the FWA sample solution was added using a Pasteur pipette until the solution was half-way up the hair. The hair swatch was left in solution for a period of 30 min at room temperature. The hair swatch was removed and squeezed to eliminate the bulk of the solution, then rinsed with fresh water and squeezed dry again. The hair was then dried on a radiator overnight. The swatches are examined under 10 ambient light and compared to a blank (same wetting / drying procedure with water) for appearance change. The results of the hair test are shown in Table 5. Table 5: Hair Test Results Structure or Compound Number Hair appearance vs blank for dark / mid brown hairs and dark natural blond hairs Hair appearance vs blank for light blond bleached hairs Visual evaluation under UV .,.¾. Benchmark (DSPB) CAS 27344-41-8 Moderate Very poor (staining caused by poor dispersion at high loading) High fluorescence but poor dispersion at high loading HO^O fjl O^N^s 0^ / OH Compound 1 Good Good, increase in whiteness of sample Reasonable fluorescence throughout sample HO^O XX °^N^s Compound 2 Excellent Excellent, significant increase in whiteness of sample Good fluorescence throughout sample HO^O Xi O^N^o —1 ^OH Compound 3 Very good Very good, notable increase in whiteness of sample Reasonable fluorescence throughout sample HO^O ru Compound 4 Moderate Moderate, some in whiteness of sample Excellent fluorescence throughout sample HO^O JUL O^N^NH b Compound 5 Moderate Very poor, yellow staining of sample at high loading Excellent fluorescence throughout sample HO^O Xx o^n^n-d Compound 6 Moderate Poor, mild yellow staining of sample at high loading Excellent fluorescence throughout sample HO^O HO^O JUL JUL O^N^NH O^N^NH OH HO Compound 7 Moderate Very poor (staining caused by poor dispersion at high loading) High fluorescence but poor dispersion at high loading JUL 0 nCnh Compound 10a Very good Very good, notable increase in whiteness of sample Excellent fluorescence throughout sample O^OH O^N^O Compound 11a Moderate Moderate, some in whiteness of sample Reasonable fluorescence throughout sample Compounds of the invention were further evaluated in hair through Hair Tress testing. Hair tresses (Bleach Blonde Product Test Light, Banbury Postiche Ltd, SWDM / 2629, lg, 6") were placed 5 inside a test tube. Solutions of FWAs in DI water (0.5% w / w) were made up and added to test tubes using a Pasteur pipette. Approximately 18 ml solution was used to cover approximately half of the hair. The tresses were left for 30 minutes before running through fingers to remove excess solution. The tresses were then rinsed in cold tap water for 30 seconds before being dried with a hair dryer (Remington Power Dry 2000, eco heat setting with one fan speed setting). The tresses were combed 5 with fingers to aid the drying process and smooth out the hairs. A blank tress was also prepared by washing in cold tap water for 30 seconds and drying as per the other tresses. A reference of 4,4-bis(2-sulfostyryl)biphenyl (DSBP, 0.5% w / w) was also prepared as per the methods for the FWAs. The tresses were then placed on a black background and assessed in ambient light by 11 panel 10 members. The panel members were instructed to rank the tresses in order of brightness, from most to least, and the results are shown below in Table 6. Table 6: Hair Tress Panel Screen Structure Brightness ranking from panel tests Visual evaluation under UV (365 nm) DSBP (Benchmark) CAS: 27344-41-8 .- >. ..V x'’ s,--" 2 High fluorescence and good dispersibility. Appears more yellow compared to TSCL FWAs o o o / 3 High fluorescence and good dispersibility. Appears more blue than DSBP 5 Moderate fluorescence, good dispersibility o Xo" 1 Low fluorescence, moderate dispersibility Blank 4 No fluorescence 15 Compounds of the invention were further evaluated in hair through Shampoo testing. A shampoo was made, with the following formulation, as shown in Table 7: Table 7: Shampoo Formulation Component Inclusion (wt.%) Water Balanced to 100 Sodium lauroyl sarcosinate 5 Cocamidopropyl Betaine 1.5 Polyquaternium-7 0.2 Carbomer 0.5 Panthenol 0.5 Gluconolactone, sodium benzoate, calcium gluconate 1 Sodium hydroxide q.s. 5 Hair tresses (Bleach Blonde Product Test Light, Banbury Postiche Ltd, SWDM / 2629, lg, 6") were placed inside a test tube. Solutions of FWAs in shampoo (0.5% w / w) were made up and added to test tubes using a Pasteur pipette. Approximately 18 ml solution was used to cover approximately half of the hair. The tresses were left for 5 minutes before running through fingers to remove excess solution. The tresses were then rinsed in cold tap water for 30 seconds before being dried with a hair dryer 10 (Remington Power Dry 2000, eco heat setting with one fan speed setting). The tresses were combed with fingers to aid the drying process and smooth out the hairs. A blank tress was also prepared by washing in cold tap water for 30 seconds and drying as per the other tresses. A reference of Blueberry mica powder (0.5% w / w, The Soapery) was also prepared as per the methods for the FWAs. 15 The tresses were then placed on a black background and assessed in ambient light by 11 panel members. The panel members were instructed to rank the tresses in order of brightness, from most to least, and the results are shown in Table 8. Table 8: Shampoo Testing Structure Brightness ranking from panel tests Appearance in long wavelength UV (365 nm) Mica (Benchmark) 2 No fluorescence. Contains: 77019, 77891, 77007, 77491, 77742 \ / o o o / 4 Moderate fluorescence, good dispersibility. o o o / 1 High fluorescence, good dispersibility. Blank 3 No fluorescence. EXAMPLE 6: Solution and Emulsion Testing Compounds of the invention were assessed for their foaming properties, and the results of these tests 5 are shown in Table 9. Solutions (1% w / w) were made up of the FWAs in DI water in 30 ml vials. The samples were shaken vigorously by hand for 10 seconds then were left to stand. Samples with free acid groups were adjusted to pH 7.5 with sodium bicarbonate (IM). A foam height measurement was taken with a ruler 10 at each time point. Table 9: Foam Test Results Structure TO T5 min T30 min 0 s-y __ ''O'-' Soluble but no foam No foam No foam TZ ^=° [ z—Z Not very soluble but slight foam No foam No foam o o o / Readily soluble but no foam No foam No foam 0 Readily soluble but no foam No foam No foam 0 S—' Slightly soluble but no foam No foam No foam zz Not readily soluble but foams Large amount remains Minimal / o o a4 Not readily soluble but foams Minimal foam Only one layer of surface bubbles remains 0 nVr» °~0 Not readily soluble, seem to hydrate slightly but no foam No foam No foam F o ) o \□ -,-w 6 3 o o—' Soluble with foam No foam No foam, slight sediment forming at bottom of vial .a o o / ° Soluble but no foam No foam No foam o / =( —' o o ° Soluble at pH 7.5 but still some sediment, 1.5 cm foam height 1.0 cm foam height 0.7 cm foam height O^OH 0^ N^% Soluble at pH 7.5 but still some sediment, 1.0 cm foam height 1.0 cm foam height, with denser foam up to 0.5 cm 1.0 cm foam height H °Yn^n-1 1 O^N^O Readily soluble with 0.3 cm foam 0.2 cm foam height No foam °Y°^q^0\ O^N^O Not readily soluble (oily) and no foam No foam No foam o \ — o \ °7 $ / °z ( O \ / Readily soluble with 0.6 cm foam 0.3 cm foam height 0.1 cm foam height As shown in Table 9, many of the FWAs of the invention are readily soluble. Some of the less soluble examples can be solubilised through use of a buffer or alternative solvent addition to improve their solubility. Foaming properties, including foam thickness and stability, can be controlled with FWAs compounds of the invention. For sensorial benefit, a high foaming compound may be preferred in hygiene applications such as shampoos, hand-, face- or body-soaps but may have to be balanced with ease of rinsing. For manufacture processing benefit or for coating and spreading benefit during use, a low foaming compound may be preferred in water-in-oil or oil-in-water cosmetic applications such as foundations, protective or body creams, lotions, serums, hair conditioners. Examples of samples with good foaming are shown in Figure 2. This image also shows the different types of foam that can be achieved with the sample on the left having a denser portion below the less dense portion. Foaming behaviour of the described FWAs, with respects to both foaming height and stability, can be heavily modulated through judicious choice of core and side chain. Compounds of the invention were assessed for their emulsification properties, and the results of these tests are shown in Table 10. To test the emulsification properties of the FWAs, grapeseed oil (20% w / w) was added to the foam test vials and shaken vigorously by hand for 30 seconds. Appearance was assessed and results are recorded in Table 10. Table 10: Emulsification Test Results Sample Appearance 0 s-v o--v,o,___ 0" Emulsion formed 3? °^ZI zx Separated immediately o o / ° Emulsion formed O—< KH o o <2 Emulsion formed xz \=o «zS / z—Z o Separated immediately 0 H S— / Separated quickly 0 -o^o^o^ro Emulsion formed zx Separated immediately o ) 3 T UH 0 3 ^O o^ Separated immediately h9 o o / ° Separated immediately 1 o ° / —x / 7 o Emulsion formed O^OH O^N^O Emulsion formed H °Yn^n-1 1 Emulsion formed o \ — ° \ ° $ / °z < O \ / Emulsion formed As shown in Table 10, some of the FWAs of the invention have the ability to form emulsions, so could contribute to the overall stability of a cosmetic product, modify its texture, or be easily incorporated into products with different properties. EXAMPLE 7: Contact Angle Test Summary Compounds of the invention were assessed for their contact angle properties, and the results of these tests are shown in Table 11. The contact angle of a droplet gives an indication on the surface tension between a solution and a surface. A lower surface tension means a lower contact angle and a droplet more spread on that surface, so a higher wetting of the surface. Stock solutions (1% w / w) were made up of the FWA in DI water. Samples were inverted several times to disperse the FWAs and any that were not readily soluble were reagitated before dispensing. A test surface was prepared by coating a melamine plate with a thin layer of vegetable oil, by dispensing the oil onto some blue roll then wiping the surface, ensuring an even coat. A blank reference of DI water was then placed down onto the test plate before individual aliquots (10 pL) of the stock solutions were placed next to it. Images of the samples were taken at TO and T5 min using a MicroCapture Plus digital microscope, and the changes in contact angle were recorded as shown in Table 11. Table 11: Contact Angle Testing Structure Wettability Change in contact angle (°) Deionised water Poor 0 Benzalkonium chloride Excellent 10 Ecosurf Excellent 20 Span 20 Excellent 30 0 s-v __ 0-" Mild 10 O 0“ O0 o o o / Moderate 20 o / =( ' o O ° Moderate 25 O^OH O^N^O Excellent 30 H °Yn^n" 1 1 Excellent 30 / \ o / o / O ? o / —\ / o Excellent 40 As shown in Table 11, FWA ingredients of the invention can be tailored to provide different wetting properties and could influence the deposition, spreading or penetration of a cosmetic formulation and its other ingredients, so modify the sensorial properties when such formulation is applied to a surface 5 of the body or hair.

Claims

1. A composition comprising a fluorescent whitening agent or optical brightener of formula (I) for use in personal care, comprising at least one fluorescent whitening agent or optical brightener of formula (I) and adjuvants, wherein the fluorescent whitening agent or optical brightener of formula (I) has the structure:wherein:A is C(R1R2)(CH2)n wherein R1 is H, CH2OH or COY, R2 is H or CH2OH and wherein n is 1 or 2, or wherein A is an optionally substituted aromatic or heteroaromatic ring fused with N and X wherein N and X are respectively bound to adjacent carbon atoms on the ring;Xis O, SorNR3;the or each Y is independently OM, OR3, O(CH2)qSO3M, NHOH, NHR3, NR32, or X'L, wherein,M is selected from an alkali metal or an alkaline earth metal;the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units;q is 1 to 5; andalternatively, NR32 represents a heterocyclic ring; andwhen Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (II) having X' as defined above in place of Y.

2. The composition according to Claim 1, wherein the fluorescent whitening agent or optical brightener of formula (I) is formula (la):whereinZisO, or-NH;Xis S, O, or-NR3;the or each R1 is independently H or -C(O)ZR3;and the or each R3 is independently selected from hydrogen, a linear or branchedalkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units;wherein, when the or each R3 is a linear alkyl, it is a C7-C34 alkyl, and when the or each R3 is a branched alkyl, it is a C1-C34 alkyl.

3. The composition according to Claim 1, wherein the fluorescent whitening agent or optical brightener of formula (I) is selected from, either, formula (lb), or formula (Ic):whereinZisO, or-NH;Xis S, O, or-NR3;the or each R1 is independently H or -C(O)ZR3;and the or each R3 is independently selected from hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a linear or branched polyether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units.

4. A composition comprising a fluorescent whitening agent or optical brightener of formula (II) for use in personal care, comprising at least one fluorescent whitening agent or optical brightener of formula (II) and adjuvants, wherein the fluorescent whitening agent or optical brightener of formula (II) has the structure:R (II)wherein:R is H, CHR5R6, R5, R6, an alkylsulphonate, a polyether, an optionally substituted aromatic or heteroaromatic ring, CH2COY or CH(COY)((CH)nCOY) in which each Y is the same or different;the or each Y is independently OM, OR3, O(CH2)qSO3M, NHOH, NHR3, NR32, or X'L, wherein,M is selected from an alkali metal or an alkaline earth metal;the or each R3 is independently hydrogen, a linear or branched alkyl, a linear or branched alkenyl, an aryl, an alkaryl, an aralkyl, a linear or branched alkyl alcohol, a linear or branched alkyl alcohol polyol, a hydroxyalkylamine, a linear or branched alkylamine, a polyhydric alcohol, a sugar, a linear or branched alkyl ether, a polyester having from 2 to 1000 repeat units, or a polyoxyalkylene chain having from 2 to 1000 repeating units;q is 1 to 5; andalternatively, NR32 represents a heterocyclic ring; andwhen Y is X'L, X' is O, S or NR3, and L is a linker moiety connected to least one repeating unit of formula (II) having X' as defined above in place of Y; and R5 and R6 independently represent hydrogen, alkyl, alkenyl, vinyl, phenyl, hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl, aminomethyl, 1-(dimethylamino)methyl, 5-aminopentyl, or cyano, optionally wherein R4 and R5 are the same or different, and n is 1 or 2.

5. The composition according to any one of Claims 1 to 4, wherein the fluorescent whitening agent or optical brightener surfactant is biodegradable.

6. The composition according to any one of Claims 1 to 5, wherein the adjuvants are cosmetically acceptable carriers or auxiliaries.

7. The composition according to Claim 6, wherein the adjuvants are selected from colorants, fragrances, emollients, surfactants, humectants, thickeners, stabilisers, preservatives, pH adjusters and pH buffers, UV-absorbers, silicones, chelating agents, film-forming agents, natural extracts, antioxidants, disinfectants, and / or antimicrobials.

8. The composition according to any one of Claims 1 to 7, wherein the fluorescent whitening agent or optical brightener is present in from about 0 to about 15 wt.%, from about 0 to about 10 wt.%, from about 0 to about 5 wt.%, or from about 0 to about 2 wt.%.

9. A formulation of the composition according to any one of Claims 1 to 8, for use as a personal care product.

10. The formulation according to Claim 9, comprising further adjuvants, additives, and / or components to alter and / or control the properties of the formulation or composition.

11. Use of the composition according any one of Claims 1 to 8, or the formulation according to any one of Claims 9 to 10, in a personal care product.

12. The use according to Claim 11, in a haircare product, skincare product, dental care product, or a UV-protection product.

13. A personal care product comprising a fluorescent whitening agent or optical brightener composition according to any one of Claims 1 to 8.T +44(0)30 0300 2000A

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