Substantivity and Retention

We have touched briefly on how reduced vapour pressures can lead to reduced rates of evaporation. This means that physicochemical properties not only influence perfume volatility per se but also affect other aspects of fragrance behaviour, such as substantivity and retention. These terms are used within the industry to denote perfume longevity in use, usually with respect to a particular substrate and/or surface (e.g. skin, hair, cloth, etc.). 

To understand perfume behaviour on these surfaces and/or matrices, we must consider the range of attractive or repulsive forces between the perfume components and the surface itself. The situation is complicated by the way in which perfume is delivered to the surface. For example, for a perfume ingredient in a soap bar to be substantive it must first be efficiently delivered to the skin during washing, it must then survive rinsing and, finally, it must be retained for some time on the skin. Definitions of substantivity and of retention vary, but here retention is used to indicate the affinity a perfume has for a substrate when delivered to it, whilst substantivity also includes delivery barriers. 

In fact, several well known models in the literature allow solubilities in water to be estimated reasonably well from a knowledge of log P (and according to the functional groups present). For example, Hansch et al. (1968) has published several linear free energy relationships (LFERs) between molal solubility and log P for various classes of monofunctional molecules. The correlation coefficients for the LFERs (a measure of goodness of fit ) were in the range 0.93-0.99, indicating that solubility estimations, at least for some classes of material, are likely to be relatively accurate. 

We may conclude from the above that values of log P appear to give some guidance to the tendency of perfume ingredients to move from aqueous systems to (presumably) less polar surfaces (skin, hair, etc.). 

Analogous partition data are available for solvents other than octanol, e.g. olive oil, and these may be more pertinent in certain situations. However, log P values based on octanol/water partition are easily accessible for thousands of substances and, for most of the compounds found in perfumery, may be estimated reasonably well using one of the mathematical prediction models described in the literature [the two most well known are those due to Rekker (1977), and to Leo et al. (1971)]. Additionally, it is often true that for many materials partition coefficients determined in different solvent-water systems often correlate strongly with one another. 

We have touched briefly on how reduced vapour pressures can lead to reduced rates of evaporation. This means that physicochemical properties 

In fact, several well-known models in the literature allow solubilities in water to be estimated reasonably well from knowledge of logP (and according to the functional groups present). For example, Hansch et al. (1968) has published several linear free-energy relationships (LFERs) 

In the last decade, a significant number of applications for patents have been filed in the perfume arena that protect perfume formulations designed for longevity and substantivity (see under Patents in 

References). Such patents can encompass a wide perfume formulation space because the scope of their claim is defined in terms of the parameters described above, rather than by compound name. Particular mention may be made of the patents disclosing Enduring Perfumes and their inverse Blooming Perfumes (assigned to Procter Gamble), which recognised the importance of log/3 and boiling points, and pioneered their use in the patent literature. 

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The Q is put into QSAR by describing the structure of a compound in a quantitative way, the simplest examples of quantitative descriptors being the mass of the compound or the number of atoms present. When the compound is described using physical, as opposed to structural, properties the relationship becomes a PAR. Correlations of this type have been used in the perfumery industry to describe and predict the substantivity and retention of fragrance ingredients that is, the ability of a compound to stick to and remain bound to surfaces such as hair, skin or cloth (see Chapter 11 for more details). 

I would like now to discuss a third major area of TSCA -- the recordkeeping, retention, and reporting of information under Section 8 of TSCA. The basic purpose of this information gathering mechanism of TSCA is to assist EPA in acquiring information necessary for the Agency s various regulatory activities under the Act. Section 8 is not a substantive regulatory provision. It functions as an adjunct to other provisions to provide EPA with the information relevant to the evaluation of the health or environmental effects of chemical substances. 

For the levorotatory isomer the most important primary effects are Xi and X2. Hence for this enantiomer replacement of the carbonyl with a thiocarbonyl has a substantive impact on retention whereas replacing the H with Me on the aryl s 3 has almost no effect on retention. The dominant primary effect is still due to X2. 

A PAE resin mnst be retained on the surface of the paper fibre before it can impart wet strength to the paper. The cationic nature of PAE resins makes them naturally substantive to the anionic sites of paper fibres. Any factors that interfere with this initial mechanism will resnlt in poor retention of the PAE resin and, conseqnently, lower than expected levels of wet strength in the paper. 

Uses Antistat, humectant in cosmetics substantive protein moisturizer, fiim-former, conditioner for hair care, skin care protectant, foaming agent for detergents coating adhesive, pigment structuring agent, and fiber retention aid in paper/paperboard in contact with dry food... 

Silicone resins, particularly siloxysilicates, are utilized in conditioning formulations for several purposes. These materials have been reported to increase the deposition and substantivity of dimethicone or dimethiconol fluids. Substantivity increases markedly as the proportion of resinous silicone to dimethylsiloxane increases, the improvement being directly related to the decreased solubility of the resin. Multilayer deposition is reported to be limited thus buildup is not considered to be an issue (92,100,174). Siloxysilicate resins have also been utilized in conditioning formulations to impart mild set retention properties to the hair. In addition to daily use conditioning products, the silicone resins may be incorporated into hairsprays, mousses, gels, and so forth, to provide humidity resistance as well as improved set retention properties, without detracting from dry hair aesthetics. The silicone resins are frequently formulated into these products in conjunction... 

Chemical products used for mold-proofing can be applied to the surface of the paper or board at the size press, coater, water box or some other surface treatment. The obvious advantage here is 100% retention of the moldproofing agent onto the product and better efficiency. The disadvantage is exposure to biocide and in some cases no such feed point exists. Biocides may also be added to the pulp slurry. In this case, the product or blend of products must adhere to the fibers. This is referred to as the product s substantivity. 

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