Self-Assemblies of Chiral D-Glucamine Appended π-Chromophores: Effect of Borate Solution, Hydrogel Network Formation, and Linear/Nonlinear Rheological Behaviors.

This study investigated the influence of molecular structure on optical and rheological properties of self-assembled networks. Three amphiphilic derivatives were synthesized by functionalizing chiral D-glucamine (glu) with different π-chromophores: perylene diimide (PDI-glu), dibrominated perylene diimide (Br2-PDI-glu), and naphthalene diimide (NDI-glu). The synthesized derivatives consisted of hydrophilic glu moieties and hydrophobic π-surfaces as the core, which drove their self-assembly properties in water. Photophysical properties of assemblies were characterized using UV-vis, photoluminescence (PL), circular dichroism (CD), and time-correlated single-photon counting (TCSPC) spectroscopic techniques. Hydrogels, which were prepared successfully in borate solution (1 M, pH = 8.5), revealed the formation of robust fibrillar networks attributed to the combination of π-π surface stacking interactions and dynamic cross-linking through intermolecular syn-diol interaction between the glucamine and the borate ion. The rheological performances of networks were extensively investigated in both linear and nonlinear viscoelastic regimes. To gain deeper insight into their microstructural response, 3D Lissajous-Bowditch curves were analyzed and key nonlinear parameters ( G M ' , G L ' , η M ' , and η L ' ) were calculated. From those moduli, the strain-stiffening (S) and shear-thinning (T) parameters were derived for each network, providing the quantitative relation between the structure of the chromophore and the rheological responses.