Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structure. 5. Solid State <sup>13</sup>C NMR Characterization of Motion and Conformations of Methylene and Mesogen Groups in Different Mesophases of TPP(<i>n</i> = 12 and 15)

Cheng, Jin; Yoon, Yeocheol; Ho, Rong‐Ming; Leland, Mark; Guo, Mingming; Cheng, Stephen Z. D.; Chu, Peng-Cheng; Percéc, Virgil

doi:10.1021/ma970177m

Cited by 17 publications

(25 citation statements)

References 19 publications

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“…One of the advantages of solid-state 13 C NMR is that it can give a quantitative population estimate of the ordered (alltrans) and disordered (mixture of trans and gauche) alkyl tail conformations. 1,36,[44][45][46][47][48] Figs. 8a and 8b show CP/MASS/DD and Bloch decay spectra of C12PhBA during heating at different temperatures, respectively.…”

Section: Hydrogen Bonding Associations and Molecular Mobility In The ...mentioning

confidence: 99%

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Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

et al. 2006

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A series of symmetrically tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamides (CnPhBA, where n is the number of carbon atoms in the alkyl chains, n = 10, 12 and 16), was synthesized in order to investigate the effect of alkyl chain length on supra-molecular ordered structures induced by hydrogen (H)-bonding and micro-phase separation. These bisamides consist of a rigid aromatic bisamide core with three flexible alkyl chains at each end of the core. Major phase transitions and their origins in CnPhBA bisamides were studied with differential scanning calorimetry, one-dimensional (1D) wide angle X-ray diffraction (WAXD), infrared spectroscopy, and solid-state carbon-13 nuclear magnetic resonance experiments. The structures of these compounds in different phases were identified using 2D WAXD from oriented samples and were also confirmed by selected area electron diffractions in transmission electron microscopy from stacked single crystals and by computer simulations. All of the CnPhBA bisamides in this series formed a highly ordered oblique columnar (W OK ) phase and a low-ordered oblique columnar (W OB ) phase, similar to a recent report on C14PhBA.1 The two main driving forces in the formation of these two supra-molecular columnar structures were identified: One was the H-bond formation between N-H and CLO groups, and the other was the micro-phase separation between the bisamide cores and the alkyl chains. With increasing the length of alkyl tails, the isotropization temperature decreased, while the disordering temperature of the alkyl tails increased. The 2D lattice structures perpendicular to the columnar axis also increasingly deviated from the pseudohexagonal packing with increasing the alkyl tail length. However, the alkyl tail length did not have a significant influence on the packing along the columnar axis direction. Utilizing polarized optical microscopy, the phase identifications were also supported by the observation of texture changes and molecular arrangements inside of the micro-sized domains.

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Section: Hydrogen Bonding Associations and Molecular Mobility In The ...mentioning

confidence: 99%

“…1,36,[44][45][46][47][48] Figs. 8a and 8b show CP/MASS/DD and Bloch decay spectra of C12PhBA during heating at different temperatures, respectively.…”

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Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

et al. 2006

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“…Furthermore, TPP( m = 12) possesses two crystalline phases, K 1 and K 2 , which do not exist in TPP( n = 7). The transition thermodynamic properties (temperatures and heats of transitions) are also different in these TPPs. − Molecular dynamics in different phases, surface-induced phase structures, , and structural and morphological development in TPPs 8,9 have also been investigated.…”

Section: Introductionmentioning

confidence: 99%

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 7. Phase Structures in a Series of Copolyethers Containing Odd and Even Numbers of Methylene Units of Different Compositions

et al. 1999

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A series of liquid crystalline copolyethers have been synthesized from 1-(4-hydroxy-4‘-biphenyl)-2-(4-hydroxyphenyl)propane with 1,7-dibromoheptane and 1,12-dibromododecene [coTPPs(7/12)], which represents copolyethers containing both odd and even numbers of methylene units. The molar ratio of odd to even methylene units in this series ranges from 1/9 to 9/1. The coTPPs(7/12) exhibit multiple phase transitions during cooling and heating in differential scanning calorimetry experiments. For all these thermal transitions, a small undercooling and superheating dependence is observed upon cooling and heating at different rates. Three types of phase behaviors can be classified in coTPPs(7/12) on the basis of the structural analyses by wide-angle X-ray diffraction on powder and fiber samples and by electron diffraction experiments in transmission electron microscopy. At room temperature, highly ordered smectic and smectic crystal (SC) phases are identified in coTPPs(7/12: 1/9 and 2/8), which is similar to the homopolymer TPP(m = 12). The coTPPs(7/12: 3/7, 4/6, and 5/5) possess a hexagonal columnar (ΦH) phase in which the molecular and columnar axes are parallel to the fiber direction and perpendicular to the hexagonal lateral packing. The coTPPs(7/12: 6/4, 7/3, and 8/2) possess a tilted hexagonal columnar (ΦTH) phase with a single tilt angle which increases with the increasing composition of the seven-numbered methylene units. However, in coTPP(7/12: 9/1), a ΦTH phase with multiple tilt angles is found. Upon heating, phase structures in most coTPPs(7/12) involving the columnar phases enter directly into the nematic (N) phase, while the coTPP(7/12: 1/9) exhibits a highly ordered smectic F (SF) phase before it reaches the N phase. One exception is found in coTPP(7/12: 2/8), wherein the transformation from the SF to ΦH occurs prior to the N phase. Combining the copolymer phase behaviors observed with the corresponding homopolymers TPP(n = 7) and TPP(m = 12), a phase diagram describing transition temperatures with respect to the composition can be constructed.

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“…These solid-state 13 C NMR experiments provided information on the fraction of ordered (all-trans) and disordered (mixture of trans and gauche) conformations in the alkyl chains and the mobility of each carbon in a-6TTF12 in different phases at various temperatures. [61][62][63][64][65] These results show that the alkyl chains are frozen in the amorphous state after the high temperature transition and are nearly crystalline (90% trans conformation) at the low temperature transition. By combination of DSC (Figure 2), 1D WAXD (Figure 3), and solid-state 13 C NMR ( Figures S2 and S3 in the Supporting Information) results, it can be concluded that a-6TTF12 exhibited two ordered phases below T i .…”

Section: Resultsmentioning

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Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules

et al. 2009

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A series of swallow-shaped tetrathiafulvalene (TTF)-based liquid crystal (LC) molecules (a-6TTFn, where 6 represents the number of carbon atoms in the two tails of a-6TTFn and n is the even number of carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen, n = 6-12) was designed and synthesized. One of this series of swallow-shaped asymmetric TTF molecules (abbreviated as a-6TTF12) having 12 carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen served as an example in this study. Major phase transitions and their origins in a-6TTF12 were studied with combined techniques of differential scanning calorimetry (DSC), one-dimensional (1D) wide-angle X-ray diffraction (WAXD) and solid-state carbon-13 ( 13 C) nuclear magnetic resonance (NMR) experiments. a-6TTF12 formed a highly ordered liquid crystalline (Φ LC ) phase at higher temperatures and a crystalline (Φ Cr ) phase at lower temperatures. On the basis of the experimental results, it was found that the highly organized columns in the Φ LC phase partially lost their long-range positional order compared with the Φ Cr phase at lower temperatures due to the distinct molecular packing of alkyl chains during the transition from Φ LC T Φ Cr . Furthermore, it was realized that there are two main driving forces in the formation of the ordered columnar phases. One was the π-π interaction among the TTF-based mesogens, and the other was the nanophase separation between the rigid TTF-based mesogens and the flexible alkyl chains. The structure, molecular packing symmetry, and morphology of a-6TTF12 in different phases were identified using 2D WAXD together with selected area electron diffraction (SAED) from transmission electron microscopy (TEM). Bright-field TEM images of polyethylene-decorated films of a-6TTF12 allow us to confirm its molecular self-organization which was first identified by SAED as well as by 2D WAXD from oriented films. Morphological observations utilizing cross-polarized optical microscopy (POM) on the micrometer length scale validated the phase transitions and molecular orientation in the macroscopically oriented film.

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Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structure. 5. Solid State ¹³C NMR Characterization of Motion and Conformations of Methylene and Mesogen Groups in Different Mesophases of TPP(n = 12 and 15)

Cited by 17 publications

References 19 publications

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 7. Phase Structures in a Series of Copolyethers Containing Odd and Even Numbers of Methylene Units of Different Compositions

Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules

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Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structure. 5. Solid State 13C NMR Characterization of Motion and Conformations of Methylene and Mesogen Groups in Different Mesophases of TPP(n = 12 and 15)

Cited by 17 publications

References 19 publications

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Phase behaviors and supra-molecular structures of a series of symmetrically tapered bisamides

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 7. Phase Structures in a Series of Copolyethers Containing Odd and Even Numbers of Methylene Units of Different Compositions

Self-Assembled Columnar Structures of Swallow-Shaped Tetrathiafulvalene-Based Molecules

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Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structure. 5. Solid State ¹³C NMR Characterization of Motion and Conformations of Methylene and Mesogen Groups in Different Mesophases of TPP(n = 12 and 15)