Spring-2014-尿素衍生物小分子凝胶Urea derivatives as low-molecular-weight gelators.pdfVIP

J Incl Phenom Macrocycl Chem (2013) 77:33–48 DOI 10.1007/s10847-013-0299-9 REVIEW ARTICLE Urea derivatives as low-molecular-weight gelators Masamichi Yamanaka Received: 31 January 2013 / Accepted: 16 February 2013 / Published online: 27 February 2013 Springer Science+Business Media Dordrecht 2013 Abstract This paper reports an overview of low-molec- research, cosmetics, and medical instruments, have been ular-weight gelators (LMWGs) that have a ureide moiety realized [ 1]. Gels are classified into two groups: chemical as a hydrogen-bonding site. Various mono-, bis-, tris-, and gels, which have covalent cross-linking, and physical gels, tetrakis-urea compounds can form supramolecular gels which have noncovalent cross-linking. Supramolecular with organic solvents. The author developed a C3-sym- gels constructed from the self-assemblies of small mole- metrical tris-urea molecule that can form a ubiquitous cules called low-molecular-weight gelators (LMWGs) are framework of LMWGs. The supramolecular organogel of a type of physical gel. The general processes for the for- the tris-urea molecule exhibited a chemical-stimuli- mation of supramolecular gels are as follows. An LMWG responsive reversible gel–sol phase transition. Supramo- is self-assembled in one dimension to produce supramo- lecular hydrogels are constructed from self-assemblies of lecular polymers [2, 3]. The resulting pseudo -polymers are amphiphilic urea derivatives. Sugar-connected amphiphilic bundled to form a fibrous aggregate that is tens to hundreds tris-urea was found to form a gel with water, and the of nanometers thick and has a high aspect ratio. Several hydrogels showed chemical-stimuli-responsive gel–sol such fibrous aggregates are