Effects of molecular flexibility and head group repulsion on aramid amphiphile self-assembly

Abstract

Strongly interacting amphiphilic molecules self-assemble in water. The flexibility of the amphiphiles and their head group repulsion mediate their nanostructure geometry.

Geometric Transformations Afforded by Rotational Freedom in Aramid Amphiphile Nanostructures

“…Previously, we confirmed that a bathochromic shift indicates a reduced intermolecular interaction for self-assembled AA nanostructures. 31,40 However, we also confirmed from solution WAXS that the hydrogen bonding network among D-AAs is activated when bathochromic shifts occur at high concentrations (Figure 3b). Hence, we consider that the different packing preference at low and high concentrations is caused by the conformational changes of D-AA, which lead to the shifts and changes in the UV−vis spectra's peak ratios.…”

“…14 However, changes in pH conditions can influence this due to the positively charged surface chemistry. 31 In this study, we maintain the same hydrophilic headgroup of two AAs in order to eliminate any morphological changes that may be related to the headgroup chemistry. Unlike the assembly of CatAAs, the assembly of D-AAs in water shows explicit dependence on the concentration and temperature by conventional transmission electron microscopy (TEM) and cryogenic TEM (cryo-TEM) (Figure 1b).…”

Domain-Specific Phase Transitions in a Supramolecular Nanostructure

“…In all cases, we verified that nanoribbon morphologies with consistent dimensions are observed (Figure S7). 43 The site-specific dynamics of each spin-labeled nanoribbon in aqueous suspension were assessed by EPR. The NLSL and CSCA programs were used to fit the spectra with a microscopic order-macroscopic disorder (MOMD) model, which describes the EPR spectra of nitroxyl radicals with local ordering in the slow-motion regime.…”

“…Literature values for the β-sheet hydrogen bond and slipped parallel benzene π−π interaction strengths are labeled on the energy axis. 43,44 Nanoribbon schematics adapted from Biophys J., 119 (10), the activation energy of diffusion are relatively low. Nitroxide EPR spectral line shapes are highly sensitive to the intermediate time scale conformational motion characteristic of ordered/viscous liquids and flexible polymer chains and can be influenced by these rotations even if they are of low amplitude.…”

“…Error bars are calculated from the Arrhenius plot slope error (FigureS28). Literature values for the β-sheet hydrogen bond and slipped parallel benzene π−π interaction strengths are labeled on the energy axis 43,44. Nanoribbon schematics adapted from Biophys J., 119(10), Lindemann W. R. et al, Global Minimization Toolkit for Batch-Fitting and χ 2 Cluster Analysis of CW−EPR Spectra, 1937−1945, Copyright (2020), with permission from Elsevier.…”