Columnar superstructures

Size and shape Certain steric effects can be achieved using characteristically wedge-shaped dendrons. Thus, self-assembling dendrons have been connected to supramolecular aggregates with defined dimeric or hexameric structures. Such aggregates can form columnar superstructures which reveal liquid-crystalline properties. Spherical superstructures arise from the self-assembly process when conical dendrons are used14 14,161 Similar... 

In contrast, recent kinetic investigation of the polymerization of spacerless G2 dendron-substi-tuted styrene and methylmethacrylate, respectively, in solution lead to the unexpected conclusion that above a certain critical monomer concentration a strong increase in the rate of the free radical polymerization is observed [21]. The results can be explained by self-organization of the growing polymer chain to a spherical or columnar superstructure in solution, depending on the degree of polymerization (DP, Fig. 2). The rate constants and low initiator efficiency lead one to conclude that the self-assembled... 

C.D. Simpson, J. Wu, M.D. Watson, K. Mullen, From graphite molecules to columnar superstructures-an exercise in nanoscience. J. Mater. Chem. 14, 494-504 (2004)... 

J.-H. Lee, S.-M. Choi, B.D. Pate, M.H. Chisholm, Y.-S. Han, Magnetic uniaxial alignment of the columnar superstructure of discotic metallomesogens over the centimeter length scale. J. Mater. Chem. 16, 2785-2791 (2006)... 

Kim, H. S. Choi, S. M. Lee, J. H. Busch, R Koza, S. J. Verploegen, E. A. Pate, B. D. Uniaxially oriented, highly ordered, large area columnar superstructures of discotic supramolecules using magnetic field and surface interactions. Adv. Mater. 2008, 20, 1105-1109. 

Dicopper complexes, 28, have been synthesized and characterized by Lai et al. [71], These complexes melt to give birefringent fluid phases with columnar superstructures. 

Figure 7 Schematic representation of the columnar superstructures suggested by the X-ray data for (LP2, LU2) , (left) and (MP2, MU2) (right) each spot represents a PU base pair spots of the same type belong to the same supramolecular strand the dimensions are compatible with an arrangement of the PTP and UTU components along the strands indicated the aliphatic chains stick out of the cylinder, more or less perpendicularly to its axis. For (LP2, LU2) , a single helical strand and the full triple helix are, respectively, represented on the bottom and at the top of the column. For (MP2, MU2) , the representation shown corresponds to the column cut parallel to its axis and flattened out.

In this new type of nematic phase reported about ten years ago [18,19], its columnar superstructure acts as calamitic molecules do in their nematic phase and also displays a Schlieren texture, which is responsible for its name. X-ray diffraction studies [18,19] have proved the nematic array of columns. This method of mesophase induction constitutes an attractive and novel principle [9,14,17,18] for the design of tailor-made thermotropic nematogens from discotic starting materials by spontaneous supramolecular self-organisation. 

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