Gelation properties of amino-acid-based bis-urea compounds in organic solvents and in the presence of surfactants

ABSTRACT

Self-assembled systems based on low-molecular-weight gelators (LMWGs) and micelle-forming surfactants are stabilized by non-covalent and non-interfering interactions. The simultaneous self-assembly of LMWGs and surfactants in a solution could lead to the formation of fibrillar networks with encapsulated surfactant micelles. In this study, the gelation properties of amino-acid-derived low-molecular-weight bis-urea compounds in water, various organic solvents, and surfactant solutions, including anionic surfactants sodium dodecyl sulfate and dodecylbenzene sulfonic acid, cationic surfactant cetrimonium bromide, and nonionic surfactants polysorbate 80 and octyl-β-d-glucopyranoside, were investigated. In the presence of surfactants, the nature of the linker of the bis-urea compounds influences the aggregation between gelator molecules. Compounds with cyclic and aromatic linkers effectively form gels at surfactant concentrations above a critical micelle concentration (CMC). The different fiber morphologies observed for surfactant gels based on imaging analysis suggest that the structure of the bis-urea compounds influences self-assembly. Rheological measurements revealed the solid-like nature of the gels and their high thermal stability. The viscoelastic nature of the surfactant gels offers potential use in various commercial applications, including home care products.

KEYWORDS:

• Amino-acid-based bis-urea compounds
• surfactants
• supramolecular gels
• rheology modifiers
• self-assembly

Acknowledgments

This research is funded by the Natural Sciences Research Institute (NSRI) of the University of the Philippines, Diliman (CHE-20-1-03) and the UP System Balik PhD Program (OVPAA-BPhd-2017-05). We also gratefully acknowledge the following institutions who aided in the analysis necessary to complete this study: the AFM Imaging Service Facility, and the Analytical Services Laboratory (ASL) of the Institute of Chemistry, University of the Philippines Diliman; the Materials R&D and Consulting Facility at the Department of Mining, Metallurgical, and Materials, University of the Philippines Diliman; and Chemrez Technologies.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/1539445X.2023.2222388.

Additional information

Funding

The work was supported by the Natural Sciences Research Institute (NSRI), University of the Philippines [CHE-20-1-03]; UP System Balik PhD Program [OVPAA-BPhd-2017-05].