Synthesis of bio-based supramolecular gelators to act as thickeners in industrial applications

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Project background (identification of the problem and its importance and relevance to sustainability) Following a recent increase in social and environmental pressures, along with new regulations to control microplastic release into the environment; industry has put a huge focus on ensuring formulations are made from readily biodegradable, sustainable materials. Thickeners are a key component of many formulations however they are often formed of high molecular weight polymers, such as poly (acrylic acid), which are favoured for their ability to form gels at a very low weight percent. Unfortunately, these high molecular weight polymers have poor biodegradability, and are often sourced from petrochemicals, whilst bio-based polymer alternatives, such as hydroxyethyl cellulose, are costly and require heavy extraction. Thus, the challenge arises to create an alternative to high molecular weight polymers, that are bio-degradable, designed with consideration of sustainability, and that perform equally at a similar weight percentage. Proposed solution and methodology It is proposed that by designing low molecular weight structures (<2000Da) with the ability to self-assemble though supramolecular, non-covalent interactions, gels can be formed with similar properties to the polymer-based systems. When a low molecular weight gelator (LMWG) is mixed with a solvent and a stimulus is applied, non-covalent interactions (such as hydrogen-bonds, pi-pi stacking or van-der-waals forces) can lead to the formation of fibrils, which entangle together and entrap solvent molecules within the matrix forming a gel. Since the backbone of these fibrils are non-covalent, they can be broken by applying another physical or chemical stimulus, which could be tailored to conditions in waste-treatment. One of the main challenges is to design LMWG's that can form gels in polar solvents such as water and propylene glycol, as the preferred solvents in personal-care formulations. Solvent effects are complex within these systems and therefore the behaviour of gelators in different solvent systems is difficult to predict. A key part of the project will focus on expanding an existing structure-property database to improve machine learning and prediction. The project will begin with the synthesis of literature-reported gelators, aiming to obtain these structures via 'green' synthetic pathways. Using the chemistry acquired from the previous study, the project will then move toward the design of LMWGs from bio-based, waste, feedstocks such as terpenes, vanillin and macroalgae. Extensive testing of the properties of each gelator in different solvent systems and formulations will be carried out, comparing to polymer-based formulations. Rheological screening, spectroscopic imagery and toxicology studies will all be key components of this work.