[Show abstract][Hide abstract] ABSTRACT: Asymmetrically substituted amphiphilic sulfamide, N-tetradecyl-N'-(6-dimethylaminohexyl)-sulfamide (3c) having a dimethylamino group at one end of the side chain, showed a strong ability to form two-dimensional (2-D) sheet-like assemblies by the 2-D hydrogen-bond networks between sulfamide moieties. Upon protonation of the amino group with acid, the cationic ammonium form of 3c induced effective hydrogelation (minimum gelation concentration: 0.5wt%) to yield a translucent, self-standing hydrogel. Infrared (IR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies confirmed formation of the fibrous assemblies of the hydrogen-bond-directed 2-D nanosheets in the hydrogel. A novel mode of three-dimensional (3-D) networks was formed by branching and recombination of hydrogen-bond networks and knit-like linkages between the assemblies. The storage and loss moduli of the hydrogel (2wt%) were measured to be in the range of 10(2) and 10(3)Pa, showing relatively high mechanical stability.
Journal of Colloid and Interface Science 07/2013; 408(1). DOI:10.1016/j.jcis.2013.07.012 · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Guanosine derivative 1 forms hydrogen-bond-directed giant vesicles. On a silicon substrate, the vesicles retain their shape and internal water phase even after removal of external water under vacuum. Dry manipulation of the micrometer-sized vesicles was carried out via AFM-tip-induced partition and fusion of the vesicles. For larger vesicles (5-10 μm), external solutions were successfully injected through a microcapillary inserted into the vesicle in air.
Journal of the American Chemical Society 09/2012; 134(38):15684-7. DOI:10.1021/ja307231u · 12.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: By mixing a small volume of THF containing guanosine derivative 1 and tetraethylenegrycol dodecyl ether (TEGDE) with water and subsequently removing TEGDE by gel permeation chromatography, micrometer-sized giant unilamellar vesicles (GUV) of 1 were successfully prepared. The vesicle membrane was a 2-D sheet assembly of thickness 2.5 nm, composed of a 2-D inter-guanine hydrogen-bond network. The GUV dispersion showed high stability because of a large negative zeta potential, which allowed repeated sedimentation and redispersion by centrifugation and subsequent gentle agitation. TEGDE-triggered fusion of GUVs took place within 350 ms, which proceeded by fusion of the vesicle membranes in contact. These unique static and dynamic properties of the GUV membrane assembled by the 2-D hydrogen-bond network are discussed.
[Show abstract][Hide abstract] ABSTRACT: Sulfamide derivatives showed high ability to form hydrogen-bond-directed two-dimensional (2-D) sheet assemblies of nanometer thickness. Further, fine-tuning of the side chain structures and preparation conditions allowed for the formation of micrometer-sized giant vesicles of 4b in water by the simple injection method. IR and XRD studies indicated that 4b having tetradecyl and oxyethylene-terminated alkyl side chains formed hydrogen-bond-directed 2-D nanosheet pairs. SEM, AFM, and TEM observation of the dried vesicles revealed that the vesicle membrane was composed of several lamellar-stacked layers of 2-D nanosheets and showed a characteristic patchwork-like pattern on the surface.
[Show abstract][Hide abstract] ABSTRACT: A novel asymmetrically substituted sulfamide forms hydrogen bond-directed amphiphilic 2-D sheet assemblies and shows high ability to induce gelation of a variety of solvents including polar water, nonpolar dodecane and aqueous/organic biphasic systems, and this high and wide gelation ability is realized by adjusting the mode of association of the amphiphilic sheet assemblies.