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Heist LM, Poon CD, Samulski ET, Photinos DJ, Jokisaari J, Vaara J, Emsley JW, Mamone S, Lelli M. Benzene at 1GHz. Magnetic field-induced fine structure. J Magn Reson 2015; 258:17-24. [PMID: 26160011 DOI: 10.1016/j.jmr.2015.06.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 06/04/2023]
Abstract
The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the (13)C satellite doublets Δν'. This difference, Δ(Δν)=Δν'-Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the (13)C and (2)H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.
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Affiliation(s)
- L M Heist
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
| | - C-D Poon
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
| | - E T Samulski
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA.
| | - D J Photinos
- Department of Materials Science, University of Patras, Patras 26504, Greece
| | - J Jokisaari
- NMR Research Group, University of Oulu, 90014 Oulu, Finland
| | - J Vaara
- NMR Research Group, University of Oulu, 90014 Oulu, Finland
| | - J W Emsley
- Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
| | - S Mamone
- Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
| | - M Lelli
- Centre de RMN à Très Hauts Champs, Institut de Sciences Analytiques (CNRS/ENS Lyon/UCB Lyon 1), Université de Lyon, 69100 Villeurbanne, France
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Christopoulos DK, Terzis AF, Vanakaras AG, Photinos DJ. Helix formation in linear achiral dendronized polymers: A computer simulation study. J Chem Phys 2006; 125:204907. [PMID: 17144740 DOI: 10.1063/1.2378630] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a molecular simulation study of the structure of linear dendronized polymers. We use excluded volume interactions in the context of a generic coarse grained molecular model whose geometrical parameters are tuned to represent a poly(paraphenylene) backbone with benzyl ether, Frechet-type dendrons. We apply Monte Carlo sampling in order to investigate the formation of packing-induced chiral structures along the polymer backbone of these chemically achiral systems. We find that helical structures can be formed, usually with defects consisting of domains with reversed helical handedness. Clear signs of helical arrangements of the dendrons begin to appear for dendritic generation g=4, while for g=5 these arrangements dominate and perfect helices can be observed as equilibrium structures obtained from certain types of starting configurations.
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Affiliation(s)
- D K Christopoulos
- Department of Materials Science, University of Patras, Patras 26504, Greece
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Affiliation(s)
- A. G. Vanakaras
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - S. C. Mcgrother
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - G. Jackson
- b Department of Chemistry , University of Sheffield , Sheffield , S3 7HF , UK
- c Department of Chemical Engineering , Imperial College , London , SW7 2BY
| | - D. J. Photinos
- a Department of Physics , University of Patras , Patras , 26500 , Greece
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Affiliation(s)
- A. G. Vanakaras
- a Department of Physics , University of Patras , Patras , 26110 , Greece
| | - D. J. Photinos
- a Department of Physics , University of Patras , Patras , 26110 , Greece
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Affiliation(s)
- Y. Marinova
- a Institute of Solid State Physics, Bulgarian Academy of Sciences , 72 Tzarigradsko chaussee, 1784 , Sofia , Bulgaria
| | - J. Kosmopoulos
- b Department of Physics , University of Patras , Patras , 26500 , Greece
| | - W. Weissflog
- c Inst. fur Physikalische Chemie, Martin-Luther-Universität Halle-Wittenberg , Mühlpforte 1, 06108 , Halle , Germany
| | - A. G. Petrov
- a Institute of Solid State Physics, Bulgarian Academy of Sciences , 72 Tzarigradsko chaussee, 1784 , Sofia , Bulgaria
| | - D. J. Photinos
- b Department of Physics , University of Patras , Patras , 26500 , Greece
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Affiliation(s)
- A. F. Terzis
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - A. G. Vanakaras
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - D. J. Photinos
- a Department of Physics , University of Patras , Patras , 26500 , Greece
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Vanakaras AG, Terzis AF, Photinos DJ. On the Molecular Requirements for the Stabilisation of Thermotropic Biaxial Ordering in Rod-Plate Nematics. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587250108025760] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- A. G. Vanakaras
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - A. F. Terzis
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - D. J. Photinos
- a Department of Physics , University of Patras , Patras , 26500 , Greece
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Affiliation(s)
- A. F. Terzis
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - A. G. Vanakaras
- a Department of Physics , University of Patras , Patras , 26500 , Greece
| | - D. J. Photinos
- a Department of Physics , University of Patras , Patras , 26500 , Greece
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Abstract
Systematic efforts to synthesize fullerene-containing liquid crystals have produced a variety of successful model compounds. We present a simple molecular theory, based on the interconverting shape approach [Vanakaras and Photinos, J. Mater. Chem. 15, 2002 (2005)], that relates the self-organization observed in these systems to their molecular structure. The interactions are modeled by dividing each molecule into a number of submolecular blocks to which specific interactions are assigned. Three types of blocks are introduced, corresponding to fullerene units, mesogenic units, and nonmesogenic linkage units. The blocks are constrained to move on a cubic three-dimensional lattice and molecular flexibility is allowed by retaining a number of representative conformations within the block representation of the molecule. Calculations are presented for a variety of molecular architectures including twin mesogenic branch monoadducts of C60, twin dendromesogenic branch monoadducts, and conical (badminton shuttlecock) multiadducts of C60. The dependence of the phase diagrams on the interaction parameters is explored. In spite of its many simplifications and the minimal molecular modeling used (three types of chemically distinct submolecular blocks with only repulsive interactions), the theory accounts remarkably well for the phase behavior of these systems.
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Affiliation(s)
- S D Peroukidis
- Department of Materials Science, University of Patras, Patras 26504, Greece
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Galindo A, Haslam AJ, Varga S, Jackson G, Vanakaras AG, Photinos DJ, Dunmur DA. The phase behavior of a binary mixture of rodlike and disclike mesogens: Monte Carlo simulation, theory, and experiment. J Chem Phys 2003. [DOI: 10.1063/1.1598432] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Vanakaras AG, Bates MA, Photinos DJ. Theory and simulation of biaxial nematic and orthogonal smectic phases formed by mixtures of board-like molecules. Phys Chem Chem Phys 2003. [DOI: 10.1039/b306271f] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Photinos DJ, Luz Z, Zimmermann H, Samulski ET. Oblate hexaalkoxytriphenylene solutes in a prolate nematic solvent: a deuterium NMR study of alkyl chain ordering. J Am Chem Soc 2002. [DOI: 10.1021/ja00076a054] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Photinos DJ, Poon CD, Samulski ET, Toriumi H. NMR study of the effects of electric dipole interactions on the ordering of chain solutes in the nematic phase. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100199a066] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Karahaliou PK, Vanakaras AG, Photinos DJ. Tilt order parameters, polarity, and inversion phenomena in smectic liquid crystals. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 65:031712. [PMID: 11909086 DOI: 10.1103/physreve.65.031712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2001] [Revised: 10/09/2001] [Indexed: 05/23/2023]
Abstract
The order parameters for the phenomenological description of the smectic-A to smectic-C phase transition are formulated on the basis of molecular symmetry and structure. It is shown that, unless the long molecular axis is an axis of twofold or higher rotational symmetry, the ordering of the molecules in the smectic-C phase gives rise to more than one tilt order parameter and to one or more polar order parameters. The latter describe the indigenous polarity of the smectic-C phase, which is not related to molecular chirality but underlies the appearance of spontaneous polarization in chiral smectics. A phenomenological theory of the phase transition is formulated by means of a Landau expansion in two tilt order parameters (primary and secondary) and an indigenous polarity order parameter. The coupling among these order parameters determines the possibility of sign inversions in the temperature dependence of the spontaneous polarization and of the helical pitch observed experimentally for some chiral smectic-C* materials. The molecular interpretation of the inversion phenomena is examined in the light of this formulation.
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Affiliation(s)
- P K Karahaliou
- Department of Physics, University of Patras, Patras 26500, Greece
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Photinos DJ, Samulski ET. Electric dipole interactions of chain molecules in nematics: The analysis of segmental ordering in α, ω‐dibromoalkanes. J Chem Phys 1993. [DOI: 10.1063/1.464433] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lal M, Klein ML, Zerbi G, Van Beest BWH, Chachaty C, Clarke JHR, Nordio PL, Tiddy GJT, Kremer K, Ryckaert JP, Brereton MG, Michopoulos Y, Samulski ET, Yarwood J, Price SL, Boublik T, Windle AH, Burrows HD, Sellers S, Luckhurst GR, Zannoni C, Emsley JW, Pastor RW, Osguthorpe DJ, Moro GJ, Brown D, Stone AJ, Reynolds CA, Teixeira-Dias JJC, Yu K, Hamley IW, Photinos DJ. General discussion. ACTA ACUST UNITED AC 1992. [DOI: 10.1039/ft9928801775] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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