Stimuli-Responsive Designer Supramolecular Polymer Gel

• Published in: Chemistry an international journal Vol. 5; no. 1; pp. 691 - 702
• Main Authors: Douzapau, M., Roy Chowdhury, Srayoshi, Singh, Surajit, Ibukun, Olamilekan Joseph, Haldar, Debasish
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2023
• Subjects: Corrugated sheet; crystal structure; Cyclodextrins; Functional materials; gel; Hexanoic acid; host–guest complex; Hydrogen bonds; Hydrophobicity; Ions; Nanofibers; Polymer gels; Polymers; programmable; Rheology; Scanning electron microscopy; Scientific imaging; Self-assembly; Single crystals; Sol-gel processes; Stimuli; stimulus-responsive; supramolecular; Supramolecular compounds; Supramolecular polymers
• ISSN: 2624-8549; 2624-8549
• DOI: 10.3390/chemistry5010048

This paper reports a stimuli-responsive designer supramolecular polymer gel in dimethylsulphoxide (DMSO)/water (1:2) based on a dipeptide amphiphile and β-cyclodextrin (β-CD) The dipeptide amphiphile contains caproic acid at the N terminus and methyl ester at the C terminus. From X-ray single crystal diffraction, the amphiphile adopts a kink-like conformation. The amphiphile self-assembled to form a parallel sheet-like structure stabilized by multiple intermolecular hydrogen bonds. Moreover, the parallel sheet-like structure is also stabilized by edge-to-edge π–π stacking interactions. In higher-order packing, it forms a corrugated sheet-like structure stabilized by hydrophobic interactions. The dipeptide amphiphile interacts with β-cyclodextrin and forms gel through supramolecular polymer formation in (DMSO)/water (1:2) by a simple heating-cooling cycle. The sol-to-gel transformation is because of a host–guest complex between compound 1 and β-CD and the formation of supramolecular polymer accompanied by microstructure changes from nanofibers to microrods. The gel is temperature responsive with a Tgel of 70 °C. The supramolecular polymer gel is also responsive to stimuli such aspicric acid and HCl. The extensive spectroscopic studies show that the aromatic hydrophobic side chain of compound 1 forms a host–guest complex with β-CD. These results will be helpful for the design of advanced programable eco-friendly functional materials.