The beta-sheet self-assembly of an n-type NDI-dipeptide into a transparent, self-supporting hydrogel at low concentrations is described. The nanostructure of the gel is stabilized by the intermolecular pi-pi association of the NDI units and pi-pi interdigitation of the fluorene groups.

n-Type 1D nanostructures are formed from the beta-sheet assembly of dipeptides bearing a 1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI) side chain into either helical nanofibers or twisted nanoribbons. Amyloid-like 1-D helical nanofibers and twisted nanoribbons assemble in an aqueous solution depending on the placement of the NDI group. beta-Sheet-type hydrogen bonding and pi-pi association play important roles in directing the assembly process. A delicate balance between electrostatic repulsion and hydrophobic interactions is critical for self-assembly. Fluorescence lifetime and anisotropy experiments indicate that the nature of the intermolecular organization and packing within the nanostructures critically impacts intermolecular energy migration pi-electron delocalization.

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Roll up: A peptide-dendron hybrid (PDH) is capable of self-assembling into either a soluble nanotube or an amyloid-like fibrillar network. The structures interconvert on adjusting the salt concentration or pH value. Their hydrophobic interfaces efficiently encapsulate hydrophobic molecules in water which can then be released by lowering the pH value.

We prepared novel semi‐interpenetrating polymer network (semi‐IPN) materials by mixing poly(ester urethane), synthesized by the polymerization reaction between poly(ethylene glycol adipate) and toluene diisocyanate in the presence of 2,2‐bis(hydroxyl methyl) propionic acid as an extender, with nitrokonjac glucomannan (NKGM) in tetrahydrofuran and then by crosslinking and curing the mixture at 60°C for 1.5 h. Miscibility and the properties of the sheets were studied by Fourier transition infrared spectroscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry (DSC), and scanning electron microscopy. The results indicate that strong interactions between poly(ester urethane) and NKGM in the semi‐IPN sheets occurred, leading to good miscibility between the two polymers in the whole region of component ratios. When the content of NKGM was 10%, the tensile strength and breaking elongation of the semi‐IPN sheet were simultaneously enhanced to 35 MPa and 960%, respectively, compared with pure polyurethane. The DSC curves showed a low softening temperature for the poly(ester urethane), which resulted in the high elongation. By changing the NKGM amount from 10 to 90%, we prepared a series of composite materials from an elastomer to tough plastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2224–2228, 2003