Carbosilanes Crystallinity

Cr Cub, Cubv d E G HT Iso Isore l LamN LaniSm/col Lamsm/dis LC LT M N/N Rp Rh Rsi SmA Crystalline solid Spheroidic (micellar) cubic phase Bicontinuous cubic phase Layer periodicity Crystalline E phase Glassy state High temperature phase Isotropic liquid Re-entrant isotropic phase Molecular length Laminated nematic phase Correlated laminated smectic phase Non-correlated laminated smectic phase Liquid crystal/Liquid crystalline Low temperature phase Unknown mesophase Nematic phase/Chiral nematic Phase Perfluoroalkyl chain Alkyl chain Carbosilane chain Smectic A phase (nontilted smectic phase)... 

Attaching two different and incompatible chains, one an Rp-chain and at the opposite side an alkyl chain or any other chain which is incompatible with the Rp-chain (such as the carbosilane chain Rsi in compounds 188—190, Figs. 62-64) offers the possibility of creating liquid crystalline honeycombs with cells of different composition. If projected on a Euclidian plane, such a structure can be described as tiling by two or even more different color tiles (multi-color tilings) [42],... 

Moreover, polymers 6 and 8 were pyrolyzed in bulk. These pyrolysis experiments were performed in a slow stream of nitrogen and the samples were heated to 1000°C at a rate of 10°C min", remaining at this temperature for 30 minutes Both of the ceramic products were black powders and in X-ray powder diffraction studies they showed only broad peaks of low intensity, indicating the presence of mainly amorphous material To obtain crystalline materials, the ceramic products were heated slowly to 1400°C where they were held for 5 hours. The X-ray powder diffraction showed exclusively sharp peaks, characteristic of P-SiC, respectively. The increased ceramic yield obtained by pyrolysis of the metal modified carbosilane 8, as compared with the polycarbosilane 6, can be explained by an increased concentration of carbon as impurity, which was additionally evidenced by elemental analysis. 

Ponomarenko, S.A., Boiko, N.I., Shibaev, V.P., Richardson, R.M., Whitehouse, I.J., Rebrov, E.A., et al., 2000. Carbosilane liquid crystalline dendrimers from molecular architecture to supramolecular nanostructures. Macromolecules 33, 5549—5558. 

K. Lorertz, D. Holter, B. Stiihn, R. Miilhaupt, H. Frey, A mesogen-fimctionalized carbosilane dendrimer a dendritic liquid crystalline polymer. Adv. Mater. 8, 414—416 (1996)... 

S.A. Ponomarertko, L Boiko, V.P. Shibaev, R.M. Richardsort, LJ. Whitehouse, E.A. Retaov, A.M. Muzafarov, Carbosilane liquid crystalline dendrimets From molecular architectme to supramolecular nanostructures. Macromolecules 33, 5549-5558 (2000)... 

Dantlgraber, G. Baumeister, U. Diele, S. Kresse, H. LUhmann, B. Lang, H. Tschierske, C. Evidence for a new ferroelectric switching liquid crystalline phase formed by a carbosilane based dendrimer with banana-shaped mesogenic units. J. Am. Chem. Soc. 2002, 124, 14852-14853. 

Hahn, H. Keith, C. Lang, H. Reddy, R. A. Tschierske, C. First example of a third-generation liquid-crystalline carbosilane dendrimer with peripheral bent-core mesogenic units understanding of dark conglomerate phases . Adv. Mater. 2006,18, 2629-2633. 

Keith, C. Reddy, R. A. Baumeister, U. Hahn, H. Lang, H. Tschierske, C. Continuous transition from antiferroelectric to ferroelectric switching liquid crystalline phases in two homologous series of bent-core mesogenic dimers based on carbosilane spacer units. J. Mater. Chem. 2006,16, 3444-3447. 

Figure 10. Schematic diagram showing the branching structure within a carbosilane liquid crystalline dendrimer as the number of generations increases from 1 to 4.

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