Process Dependent Complexity in Multicomponent Gels

Abstract

Mixing low molecular weight gelators (LMWGs) can be used to combine favorable properties of the individual components within a multifunctional gel. Such multicomponent systems are complex enough in themselves but the method of combining components is not commonly considered something to influence self-assembly. Herein, two multicomponent systems comprising of a naphthalene-based dipeptide hydrogelator and one of two modified naphthalene diimides (NDIs), one of which forms gels, and the other does not, are investigated. These systems are probed, examining the structures formed and their gel properties (when preparing a solution from either a mixed powder of both components or by mixing pre-formed solutions of each component) using rheology, small angle neutron scattering (SANS), and absorbance spectroscopy. It is found that by altering the method of preparation, it is can either induce self-sorting or co-assembly within the fibers formed that underpin the gel network.

Keywords: co-assembly; gels; low molecular weight gelators; self-assembly; self-sorting.

Figure 1

Cartoon illustrating hypothetical examples of the different levels of complexity in a two‐component system from the primary assembly up to the tertiary assembly level.

Figure 2

Chemical structure of the molecules used in this study.

Figure 3

Cartoon showing the two different methods of preparation investigated in this study. The different colors represent different molecules used.

Figure 4

SANS from a) P* (brown) and S* (red) solutions and b) P (turquoise) and S (blue) solution. UV‐Vis absorption spectra of 1‐NapFF (black) (c) P* (brown) and S* (red) gels and (d) P (turquoise) and S (blue) gels. c) NDI‐F solution at pH 6 (pink) and d) NDI‐GF gel (purple) spectra were also shown.

Figure 5

Photographs of solutions at pH 11 and their corresponding gels.

Figure 6

Rheological strain sweeps at frequency of 10 s⁻¹ a,b) SANS data c,d) for S (blue), P (turquoise), S* (red) and P* (brown) gels. G′ are the solid shapes and G″ are the empty shapes. Rheological experiments were measured at 10 rads⁻¹ in triplicate and error was calculated from their standard deviation.

Figure 7

Hydrogel temperature sweeps for a) P (turquoise data) and S (green data) b) P* (red data) and S* (brown data). G′ are the solid shapes and G″ are the empty shapes. Tests performed at 0.5% strain and 10 rads⁻¹.