Co-Hydrogelation of Dendritic Surfactant and Amino Acids
in Their Common Naturally-Occurring Forms:
A Study of Morphology and Mechanisms1
Ning Lia, Mehran Asad Ayoubib, Huamei Chena, **, Jide Wanga, and Wei Wangc, *
aMinistry Key Laboratory of Oil and Gas Fine Chemical, College of Chemistry and Chemical Engineering,
Xinjiang University, Urumqi, 830046 China
bNovel Drug Delivery Systems Department, Iran Polymer and Petrochemical Institute, Tehran, P.O. Box 14975/112 Iran
cDepartment of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, N-5020 Norway
Correspondence to: *e-mail: wei.wang@uib.no
Correspondence to: **e-mail: chen-hua-mei@163.com
1Supplementary materials are available for this article at doi 10.1134/S1061933X19030098 and are accessible for authorized users
Received 2 March, 2018
Abstract—Sixteen different amino acids (AAs) presenting different side-chains as neutral nonpolar (Gly, Ala, Val, Leu, Ile, and Phe), neutral polar (Ser, Thr, Cys, Asn and Gln), acidic (Asp and Glu) and basic (Lys, Arg and His) could induce co-hydrogelation in 1% solutions of the dendritic surfactant, 3,3′-(octadecylazanediyl) dipropionic acid, at various concentration (1.6% ≤ Cco-hgel ≤ 20%). The amino acids Asp and Glu showed a strong favourable intercation with the surfactant, and, together with Leu and Gln, were identified as low-molecular-weight co-hydrogelators (Cco-hgel < 2%). Interpretation of XRD data indicated that all of the hydrogels exhibited lamellar structures with an occasional presence of AA crystallites. By using scanning electron microscopy, we found that the morphology of hydrogels comprises various particles (cloddy, platy, lath-/needle-like and amyloid-like fibrillar ones) and 3D structures (sheet-like and tubular ones). Furthermore, two mechanisms were identified for AA co-hydrogelation: (1) the interpenetration of AA crystallites and AA/surfactant lamellae, and (2) the formation of 3D solvent-trapping, mostly percolating structures.
DOI: 10.1134/S1061933X19030098