Self-assembly techniques, gelation

Figure 27 Self-assembly of alkylated metallocycle 93 from 120° donor, and 91 from 120° acceptor, 92. SEM images of 93 after its subsequent ordering via gelation technique in (a) acetone/water (v/v 2/1) and (b) CH2CI2 (v/v 2/1) from an initial concentration of 5.0 X M. Adapted with permission from Ref. 14CC4231. Copyright 2014 Royai Society of Chemistry.

Viscosimetry is a cheap technique and is very convenient for comparing gelators in terms of their ability to self-assemble in solution. Nevertheless, it should be restricted to Newtonian liquids (that is, liquids for which the viscosity does not depend on the shear rate (Section 2.4)), because from the capillary wall to its center the shear rate is not constant. For non-Newtonian fluids, proper viscosity calculations require corrections of the raw data once the dependency of their viscosity with the shear rate is known (Section 3.2). Unfortunately, for a given viscosimeter, the range of accessible shear rates is rather limited and it is often difficult to run measurements at very low shear rates where diluted solutions are usually expected to present a Newtonian plateau. 

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