The fractal nature of a nanofibrous network has been discovered by in‐situ measurements on fibers of N‐lauroyl‐L‐glutamic acid di‐n‐butylamide, which grow in isostearyl alcohol upon cooling; critical parameters are derived and discussed. Branching induced by crystallographic mismatch was identified as the nanofibers’ growth mechanism (see Figure for an SEM image; bifurcation positions are highlighted by dotted circles).

The architecture of three-dimensional interconnecting self-organized nanofiber networks from separate needlelike crystals of L-DHL (lanosta-8,24-dien-3beta-ol:24,25-dihydrolanosterol = 56:44) in di-isooctylphthalate has been achieved for the first time, on the basis of the completely new concept of branching creation by additives (branching promoters). [In this work, an additive, ethylene/vinyl acetate copolymer (EVACP), is used at a concentration of several 10 ppm.] We demonstrate that this novel technique enables us to produce previously unknown self-supporting supramolecular functional materials with tailormade micro- or nanostructures, possessing significantly modified macroscopic properties, by utilizing materials thus far considered to be "useless". In addition, both the self-organized structure and the properties of the new materials can be fine-tuned by altering the processing conditions. Our results show that the formation of the interconnecting 3D self-organized network structure is controlled by a new mechanism, so-called crystallographic mismatch branching mechanism, as opposed to the conventionally adopted molecular self-assembly mechanism. The principles and criteria for the selection of branching promoters are also discussed from the point of view of molecular structures.

The fractal structure of nanofiber networks formed in organogels is identified, using an in situ rheological method, together with a coupled supercritical fluid CO2 extraction/scanning electron microscopy technique. The rheological method allows us to have in-line measurements of the fractal growth of the nanofiber networks. In comparison with conventional light scattering techniques, the results obtained from this technique show much less scatter in data. Unlike conventional fractal aggregates, the growth of this type of fractal pattern is governed by a noncrystallographic branching mechanism, which occurs via self-mismatch nucleation and growth.

Supramolecular functional materials [1] with 3D fibrous network structures formed by interconnecting nanosized fibrils have important applications in, for example, drug delivery, coatings, lithography, catalyst supporters, scaffolds for tissue engineering, the engineering of nanostructural and self-supporting porous materials, and novel separation for macromolecules. [1±5] Macroscopic properties, in particular, the rheological properties of supramolecular functional materials are determined by the microstructure of fibrous networks. The fibrous networks with permanent interconnections will effectively entrap and immobilize liquid in the meshes and promote the formation of self-supporting rigid gels, which possess the elastic properties of ideal solids and the viscosity properties of a Newtonian liquid. [2,4,6] In contrast, systems consisting of nonpermanent or transient interconnecting (such as entangled) fibrils or needles reveal only viscous weak gels at low concentrations. [2] Significant efforts have been devoted to the identification of novel systems with a desirable microscopic structural organization that can enable formation of such functional materials. [2,4,5] One such route includes the screening of a large number of potential gelator/solvent systems capable of forming 3D self-organized interconnecting fibrous networks. [2, 4±7] However, through the lack of suitable of materials, screening is very difficult. Thus for a given system, it would be extremely desirable to construct or engineer interconnecting 3D fiber networks at the micro-or nanolevel with such organization that materials with the expected functionalities can be created. We aim to illustrate a completely new approach to engineering such materials by constructing permanent 3D interconnecting nanofibrous networks from a system consisting of separate fibers.The materials to be examined were obtained by dissolving lanosta-8,24-dien-3b-ol:24,25-dihydrolanosterol (L/DHL), 56:44 molar ratio, Sigma) in diisooctylphthalate (DIOP, 99 % purity, Aldrich) at approximately 125 8C, and then cooling the sample to approximately room temperature.Scanning electronic microscopy (SEM) coupled with a CO 2 super-critical fluid-extraction technique (Thar Design) was applied to examine the micro-and nanostructure of the fibrous networks. The latter technique is used to remove the liquid captured in the networks without disturbing their overall structure. [8] An opaque and viscous paste was obtained on cooling the aforementioned system (10 wt % L/DHL) to room temperature (Figure 1 a, inset). The system consists of only nonbranched fibers or needles, which are in temporary contact with each other (Figure 1 a).Our strategy is to create networks with permanent interlinking from such a system. An additive, ethylene/vinyl acetate copolymer (EVACP, (C 4 H 6 O 2 ¥C 2 H 4 ) n , M W ¼ ca. 100 000, 40 % in vinyl acetate), is introduced to achieve the microstructured architecture. Surprisingly, under identical COMMUNICATIONS

We cap silver, copper, and gold nanocolloids with long-chain alkylxanthates. In comparison to thiol capping, the particles are less hydrophobic and are stable in aqueous solutions for over a month, though being less stable than the corresponding oleate-capped particles. They can be transferred into relatively polar organic media (such as dichloromethane) but not into nonpolar solvents (such as dodecane). Unlike noncapped, thiol-capped, and oleate-capped colloids, they are temperature sensitive, as a result of the thermal decomposition of the xanthate molecule itself, and can be applied as thermally decomposable colloids. They demonstrate exceptional resistivity toward cyanide-induced corrosion by oxygen, when compared to noncapped or even to oleate-capped colloids. Xanthate capping enables the production of stable copper nanocolloids in aqueous solution under ambient conditions.