Kinetics-dominated structure and stimuli-responsiveness in the assembly of colloidal nanotubes

Abstract

In this paper, we discuss the molecular assembly kinetics of stimuli-responsive hydrogels prepared from imogolite, which is a rigid rod-like colloidal inorganic nanotube, and dicarboxylic acids. Here, the “stepwise” agglomeration of imogolite in the hydrogels gave loosely connected imogolite frameworks that induced thixotropy in hydrogels. In contrast, “simultaneous” aggregation of imogolite nanotubes led to densely packed frameworks without thixotropy in the hydrogels. The results of this study on imogolite nanotube assembly explain the self-organization mechanism of rod-like colloidal nanotubes in accordance with thermodynamic reaction kinetics. Furthermore, this study also explains the nano-architectonics of non-Newtonian fluids, enabling the design of supramolecular assemblies with non-Newtonian properties such as thixotropy. Our results describe for the first time the relationship between the microscopic molecular reaction kinetics and the macroscopic non-Newtonian properties, which have been extensively investigated.