Analysing silicone quaternary compounds

As a result of ionic interactions, the positively charged quats become substantive to the hair and skin.1 Cationic surface active compounds have performed a variety of functions in personal care applications including conditioning, antimicrobial activities, emulsification, and improving both wet and dry comb. It is therefore not surprising that the silicone analogues of traditional quats are likewise important compounds in personal care vis-à-vis conditioning and softening. The structure of the compound and the balance of silicone, fatty and water-soluble groups determines the properties of silicone quats, as is the case with all other silicone compounds. In the instance of these compounds the cationic group is a water-soluble group. Silicone quats are not new materials, in fact one early patent goes back over 30 years. This patent2 issued in 1980 discloses hair care compositions containing one or more quaternary nitrogen derivatives of trialkylamino hydroxy organosilicon compounds have superior conditioning capability for hair. Specifically, the compounds disclosed have the structure shown in Figure 1a: Wherein:

•  R is a monovalent hydrocarbon radical having from 1 to a18 carbon atoms.
•  R’ is a divalent hydrocarbon radical having from 1 to 18 carbon atoms as a divalent hydrocarbonoxy radical having from 1 to 18 carbon atoms wherein the oxygen of said hydrocarbonoxy radical is in the form of an ether linkage.
•  X– is a halide anion
•  X has an average value from 2 to 20
•  Y has an average value of from 20 to 200.

While the ‘R’ definition is defined widely, in actuality the compounds disclosed all three ‘R’ groups are CH3 (Fig. 1b). The aqueous hair conditioning compositions described by Morlino are: