Janus type molecules

Fig. 47 (a) Examples of polyphilic molecules with star shaped molecular topologies and (b) their mesophase morphologies [295]. (c) Janus-type porphyrin 177 [277] and (d) modes of self assembly of the completely RF-substituted porphyrin 156 left, for structure see Fig. 42, Colortho G -29 °C Colortho199 °C Iso) and the partly fluorinated porphyrin 177 right, ColTeJp2mg, Cr -22 °C Co n,Jp2mg 163 °C Iso) Colortho = orthorhombic columnar 3D phases (b) Reproduced with permission [295], copyright 2008, The Royal Society of Chemistry (RSC) (d) reproduced with permission [277], copyright 2011, American Chemical Society (ACS)...

Percec et al. [41,42] studied and reviewed various complex self-assembled structures in detail that can be obtained from dendritic molecules. Especially multicompartment capsules obtained by the self-assembly of a library of amphiphilic Janus-type dendrimers are impressive. The chemical linkage of two dissimilar dendritic building blocks results in Janus dendrimers and produces a break in the spherical symmetry characteristic to dendrimers. Consequently, these stmctures spontaneously promote the self-assembly upon injection of its ethanol solution to form stable unilamellar vesicular nanostructures and other complex architectures (Eig. 6.17). Dendriniersom.es... 

A recent molecular design, Janus liquid-crystalline molecular materials in the form of segmented structures that contain two different types of mesogenic units has recently been reported [108,109]. Janus materials favor different types of mesophase structure, grafted onto the same scaffold, to create giant molecules that contain different hemispheres ( Janus refers to materials with two faces, such as lluorocarbon/hydrocarbon or hydro-philic/hydrophobic, etc., for example Janus amphiphilic dendrimers have been reported [110-114]). 

As previously noted, discrete assemblies based on 1-dimensional H-bonded motifs, also termed a-networks, may be obtained by covalently tethering the H-bonding recognition arrays or by their fusion to yield Janus molecules (Fig. 2). The information manifested in the relative orientation (120°) and juxtaposition of H-bonding donor/acceptor sites (DAD/ADA), in the specific case of 5 and 6, may generate three types of association a linear ribbon or tape, a H-bonded macrocycle and an intermediate wavy ribbon or crinkled tape [46]. These structures have been characterized in the solid state by X-ray crystallographic analysis. Homochiral crinkled tapes are formed in the course... 

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