title: Ultrasound-induced gelation of fluorenyl-9-methoxycarbonyl-l-lysine(fluorenyl-9-methoxycarbonyl)-OH and its dipeptide derivatives showing very low minimum gelation concentrations.
abstract: Four l-Lysine(Lys)-l-glutamic acid(Glu) dipeptide derivatives (1-4) and their precursor-a single fluorenyl-9-methoxycarbonyl(Fmoc)-l-Lys(Fmoc)-OH amino acid (5) were demonstrated as gelators to gelate a variety of alcohols and aromatic solvents under the sonication conditions. Compared to the routine heating-cooling protocol, the ultrasound substantially brought down the minimum gelation concentrations (MGCs) of the resulting organogels. The Fourier transform infrared spectroscopy (FT-IR) and fluorescence studies revealed that the π-π stacking and hydrogen bonding act as major driving forces for the self-assembly of these lysine-based gelators into supramolecular fibrous three dimensional (3D) network, where the more the Fmoc protecting groups, the gelators are more responsive to ultrasound-stimulus and more conducive to an ordered molecular arrangement reinforcing the intermolecular forces. Moreover, the ultrasound-triggered organogels of 5 exhibited the thixotropic property. Upon imposing a mechanical shear, its gels with the fibrous 3D network structure were unraveled into sols. However, after standing quiescently over time, these sols returned to the gels showing a more ordered lamella-like packing structure as evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses.
authors.affiliation: School of Materials Science and Engineering, Beijing Institute of Technology, No. 5 South Street Zhongguancun, Beijing 100081, China; Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, No. 5 South Street Zhongguancun, Beijing 100081, China. Electronic address: genghuimin1003@163.com.
authors.forename: Huimin
authors.initials: H
authors.lastname: Geng
authors.affiliation: School of Materials Science and Engineering, Beijing Institute of Technology, No. 5 South Street Zhongguancun, Beijing 100081, China; Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, No. 5 South Street Zhongguancun, Beijing 100081, China. Electronic address: yelin@bit.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: Ye
authors.affiliation: School of Materials Science and Engineering, Beijing Institute of Technology, No. 5 South Street Zhongguancun, Beijing 100081, China; Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, No. 5 South Street Zhongguancun, Beijing 100081, China. Electronic address: zhay@bit.edu.cn.
authors.forename: Ai-Ying
authors.initials: AY
authors.lastname: Zhang
authors.affiliation: School of Materials Science and Engineering, Beijing Institute of Technology, No. 5 South Street Zhongguancun, Beijing 100081, China; Beijing Engineering Research Center of Cellulose and Its Derivatives, No. 5 South Street Zhongguancun, Beijing 100081, China. Electronic address: shaoziqiang@263.net.
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Shao
authors.affiliation: School of Materials Science and Engineering, Beijing Institute of Technology, No. 5 South Street Zhongguancun, Beijing 100081, China; Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications, No. 5 South Street Zhongguancun, Beijing 100081, China. Electronic address: sainfeng@bit.edu.cn.
authors.forename: Zeng-Guo
authors.initials: ZG
authors.lastname: Feng
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D005449:Fluorenes / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006860:Hydrogen Bonding; D008239:Lysine / Q000031:analogs & derivatives*; D008958:Models, Molecular; D013010:Sonication; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D004151:Dipeptides; D005449:Fluorenes; D005782:Gels; D008239:Lysine
keywords: Lysine-based short peptides; Organogels; Self-assembly; Ultrasound-induced gelation