Supramolecular chemistry for the application to hair dye technology

Farquhar, Lloyd

Thesis

Supramolecular chemistry for the application to hair dye technology

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Creator

Farquhar, Lloyd

Rights statement

Strathclyde Thesis Copyright

Awarding institution

University of Strathclyde

Date of award

2023

Thesis identifier

T16650

Person Identifier (Local)

201653029

Qualification Level

Doctoral (Postgraduate)

Qualification Name

Doctor of Philosophy (PhD)

Department, School or Faculty

Strathclyde Institute of Pharmacy and Biomedical Sciences

Abstract

This thesis investigates the use of co-crystallisation and crystal engineering to create novel coloured co-crystalline materials (i.e. co-crystals or salts) which can be used to colour hair. Based on the limited previous work on supramolecular hair dyes, we attempted to increase the range of available colours. Firstly, the solution reactivity of p-phenylenediamine (PPD) was investigated through the use of UV/Vis, HPLC, LC-MS and NMR spectroscopy which was monitored over three months. The colour of the PPD solutions was observed to change from colourless to a deep red/black during this time which suggested that oxidation was possibly occurring which was confirmed through the use of HPLC, LC-MS and NMR. These techniques, particularly LC-MS allowed us to identify the nature of these oxidation products. Secondly, the effect small structural changes to PPD would have on the resultant colour was investigated using o-phenylenediamine (OPD), m-phenylenediamine (MPD) and 4 iodoaniline (4IODAN). The results showed small shifts by UV/Vis occurring over time which from the PPD work in the previous chapter was more likely a result of oxidation. The impact of ionisation was also investigated through ionic co-crystals of PPD which were unsuccessful, although formation of the HCl salt did result in a colour change in the solution state. Lastly, alizarin was screened for new multi-component forms that could extend the range of available colours. A new pyridine solvate as well as three new co-crystals were identified through solution crystallisation and ball milling experiments. An additional ALZ-PHN co crystal was identified through liquid-assisted grinding (LAG) experiments which was isostructural to the ACR co-crystal. UV/Vis analysis of these new crystalline materials identified did not show any shift in colour with respect to ALZ and as a result did not offer any advantage over pure ALZ.

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