Electrogelation: Controlled Fast Formation of Micrometer-Thick Films from Low-Molecular Weight Hydrogelators

The controlled electrochemical deposition of hydrogels from low-molecular weight hydrogelators (LMWHGs) allows for the defined formation of thin films on electrodes. Here, the deposition of fibrillar networks consisting of N,N ',N ''-tris-(4-carboxyphenylene)-1,3,5-benzenetricarboxamide (BTA) onto ultraflat gold electrodes has been studied. This process, also termed electrogelation, is based on a local change in the pH due to electrolysis of water at the electrode. The protonation of the BTA sodium salt leads to self-assembly into supramolecular fibrillar structures mainly via hydrogen bonding of the uncharged molecules. The resulting hydrogel film was characterized in terms of its thickness by atomic force microscopy (AFM). Two different AFM-based techniques have been used: ex situ imaging of dried films and in situ nanoindentation of the hydrated hydrogel films. The deposition process was studied as a function of gelator concentration, applied potential, and gelation time. These parameters allow control of the film thickness to a high degree of accuracy within a few tenths of nanometers. Film formation takes place in a few seconds at moderate applied potentials, which is beneficial for biomedical applications. The results obtained for the BTA presented here can be transferred to any type of pH-responsive LMWHG and many reversibly formed hydrogel films.

Automated summary

This study investigates the controlled electrochemical deposition of hydrogel films on ultraflat gold electrodes by studying the deposition of fibrillar networks. The resulting hydrogel film, formed through self-assembly of supramolecular fibrillar structures, was characterized in terms of its thickness. The film thickness was controlled by adjusting gelator concentration, applied potential, and gelation time. This research has potential applications in the field of biomedicine.