Supramolecular Arrangement and Rheological Properties of Bisamide Gels

Journal Article (2023)
Author(s)

E. Ghanbari (TU Delft - ChemE/Advanced Soft Matter)

Zian Chen (Student TU Delft)

P. Padmanabhan (TU Delft - ChemE/Delft Ingenious Design)

S.J. Picken (TU Delft - ChemE/Advanced Soft Matter)

Jan Van Esch (TU Delft - ChemE/Advanced Soft Matter)

Research Group
ChemE/Advanced Soft Matter
Copyright
© 2023 E. Ghanbari, Zian Chen, P. Padmanabhan, S.J. Picken, J.H. van Esch
DOI related publication
https://doi.org/10.1021/acs.langmuir.3c01100
More Info
expand_more
Publication Year
2023
Language
English
Copyright
© 2023 E. Ghanbari, Zian Chen, P. Padmanabhan, S.J. Picken, J.H. van Esch
Research Group
ChemE/Advanced Soft Matter
Issue number
31
Volume number
39
Pages (from-to)
10913-10924
Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Abstract

We report a systematic study of the gelation behavior of nBA gelators in xylene, with odd and even n-methylene spacers between the amide groups (n = 5-10) and 17 carbons at each end. The melting temperatures (Tm0) of nBA gels are obtained from fitting our DSCN(T) model to the experimental DSC data. The found Tm0 of nBA gels is about 35 °C lower than Tm0 of the pure nBA gelators. This is reasonably well explained by a simple model combining theories of Flory-Huggins and Gibbs free energy of melting (FHM model). We attribute this depression to an increase in entropy upon melting of the gel due to mixing with the solvent. The odd-even alternation in Tm0 of nBA gels, which was also found for the nBA gelators, indicates that the solid structures inside the gels are somewhat similar. This was studied using XRD: similar 00l reflections were found in the XRD patterns of all nBA gels and their nBA gelators. For even nBA gels, the same reflections in the 19-25° (2θ) region confirm that the sheetlike supramolecular structure of the gels is analogous to the lamellar structure of the solid gelators. For odd nBA gels, a slight difference in the reflections around 20-25° (2θ) implies a somewhat different side-by-side packing of odd nBA gels compared to the solid state. This variation is found for all the odd gels, and indeed, they show distinctly different morphologies compared to the even nBA gels. The possible effect of this on the rheological properties is discussed using some inspiration from the Halpin-Tsai model for composites where nBA gels are considered to be analogous to composite materials. The change of the storage modulus (G') with the shape factor of woven fibers and sheets in nBA gels (20 wt %) indicates that a rheological odd-even effect might indeed be present.