Induction of Liquid Crystalline Phases: Formation of Discotic Systems by Doping Amorphous Polymers with Electron Acceptors

Abstract

9.869(1), b = 17.323(2), c = 16.083(3) A, = 94.85(1)", V = 2739.7(7) A', 2 = 4; 1606 independent reflections with I > 30(I): four-circle diffractometer, Cu,., 3" I 2 6 I 115". Lorentz, polarization, and adsorption corrections and corrections for linear decay were applied to the 3766 independent reflections collected. Anomalous dispersion corrections were applied for Co, K, and Na. The 35 non-hydrogen atoms were located using the SHELXTL Direct Methods programs and the hydrogen atom positions were located. Final cycles of least-squares refinement, which employed anisotropic thermal parameters for non-hydrogen atoms and isotropic parameters for hydrogen atoms, gave R, = 0.053, R, = 0.058. Further details of the crystal structure investigation may be obtained from the Director of the Cambridge Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road, Cambridge CB2 1 EW (England). by quoting the full literature citation.17) The twist angle T and the pyramidalization terms x, and xN were obtained from the primary torsion angles wl, w 2 , and w , as follows: T = (wl + w2)/2; xN = (w2 -0) + n) mod 2~; xc = (w, -IU, + n) mod 2x. Here we use the modified twist angle, ?: Z = (T) modn [3 a]. 7 maximizes at 2 90" and can be interpreted as the angle between the idealized positions ofthe pn orbitals on C and N. The pyramidalization terms maximize at 60". ['ayb'dl It has been found that doping electron-rich discoid polymers with electron acceptors introduces new functional behavior and, moreover, even allows the induction of mesophases in previously non-liquid-crystalline polymers. Induction of LiquidBecause of charge-transfer (CT) interactions, disc-shaped parts of side-group or main-chain polymers can be arranged in columns, which leads to discotic-columnar mesophases (Fig. 1). Although the functionalization of liquid crystals by doping has been extensively studied,"". b, dl induction of mesophases by mixing of non-liquid-crystalline substances has only been established for a few examples of rod-shaped, low molecular weight Induction of mesophases in amorphous discoid polymers is of special importance since, although numerous amorphous discoid polymers are known,f51 only a few liquid crystalline discotic polymers have been reported. [6* Polyacrylates[81 and polyesters['] containing disc-shaped, electron-rich triphenylene units were employed in these induction experiments. The induction agents were fluorenone derivatives["] with different acceptor strengths: 2,4,7-trinitrofluorenone (TNF) and 2,4,7-trinitrofluoren-9-ylidenemalonodinitrile (TNF-CN). Doping of the polymers was [ liquid crystalline discotic polymer achieved by mixing in solution." The functionalized polymers were characterized by polarization microscopy, differential calorimetry, and X-ray diffraction.["] induction of columnar mesophases in amorphous side-group polymers: The polymethacrylate 1 (T, = 30 "C) and the polyacrylate 2 (T, = -6 "C) were used as amorphous polymers containing electron-rich triphenylene side groups. [5". 81 When com...

Liquid crystallization of poly(styrene-co-maleic anhydride) induced by intermolecular hydrogen bonds

“…Recently, molecular architectures, through self-assembly, processes by specific molecular interactions, such as hydrogen-bond, 6 -10 ionic, [11][12][13] ionic-dipolar, 14 and charge-transfer interaction 15 have been recognized to be a new strategy for building the molecular structure of side-chain liquid crystalline polymers, supramolecular SLCP. Hydrogen bonding is one of the most important means of interaction for these processes due to its stability and directionality.…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…95,96 Ringsdorf et al 95 used charge-transfer interactions between electron-rich triphenylene and 2,4,7-trinitrofluorenone units to produce LC discotic polymers. Introduction of chirality into these charge-transfer polymeric complexes yields LC discotic polymers with helical order of the columns.…”

Isomorphism within the hexagonal columnar mesophase of molecular and macromolecular self- and co-assembled columns containing tapered groups

“…In an unrelated study involving main chain and side chain discotic liquid crystalline polymers, the induction of hexagonal columnar mesomorphism, its enhancement, and the induction of compatibility and mesomorphism in an incompatible polymer mixture via electron-donor acceptor interactions were reported. 4 , 24 The enhancement of mesomorphism of liquid crystalline polymers via non-covalent interactions was recently reviewed.…”