Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry

Yildirim, Arda; Krause, Christina; Huber, Patrick; Schönhals, Andreas

doi:10.1016/j.molliq.2022.119212

Cited by 2 publications

(4 citation statements)

References 55 publications

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“…Recently, the behavior of a triphenylene-based hexagonal ordered system was investigated in dependence of the length of the alkyl chain. A destringed transition from a short to a long side chain behavior is found . It might be that a similar behavior applies here, but this will need further investigations including additional systems of ILCs.…”

Section: Resultssupporting

confidence: 57%

“…A destringed transition from a short to a long side chain behavior is found. 28 It might be that a similar behavior applies here, but this will need further investigations including additional systems of ILCs. For all ILCn, a step-like change in the heat flow is observed that indicates a thermal glass transition (see Figure 2b).…”

Section: ■ Introductionmentioning

confidence: 69%

“…Spheres: ILC n ; open circles: HATn in the columnar phase taken from ref , Rhombus: Janus polynorbornenes (taken from ref ); up-pointing triangles: poly( n -alkyl methacrylate); solid line: alkyl chain length in all trans configuration. Data for poly( n -alkyl methacrylate) and all trans configuration of alkyl chains are taken from ref .…”

Section: Resultsmentioning

confidence: 99%

“…A further possible assignment for the fast γ process is the Johari Goldstein (JG) relaxation process as a precursor of the α core relaxation process. The localized fluctuations for poly (n-alkyl methacrylates) 28 and Janus polynorbornenes 29 were assigned to the JG relaxation, where the γ relaxation slows down with increasing alkyl chain length.…”

Section: ■ Introductionmentioning

confidence: 99%

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Side Chain Length-Dependent Dynamics and Conductivity in Self-Assembled Ion Channels

Kolmangadi

Smales

et al. 2022

J. Phys. Chem. C

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We study the molecular mobility and electrical conductivity of a homologous series of linear shaped columnar ionic liquid crystals ILCn, (n = 8, 10, 12, 14, 16) using broadband dielectric spectroscopy (BDS), specific heat spectroscopy (SHS), and X-ray scattering. We aim to understand how the alkyl chain length influences the dynamics and electric conductivity in this system. Two dielectrically active relaxation modes are observed, the γ and the α core process, that correspond to the localized fluctuations of the alkyl chains and cooperative motions of the aromatic core in the columns, respectively. Both the γ relaxation and the α core process slow down with increasing alkyl chain length. SHS reveals one relaxation process, the α alkyl process that has a similar temperature dependence as that of the α core process for ILC12, 14, and 16 but shifts to higher temperature for ILC8 and 10. For ILC12, 14, and 16, the absolute values of DC conductivity increase by 4 orders of magnitude at the transition from the plastic crystalline to hexagonal columnar phase. For ILC8 and 10, the DC conductivity behavior is similar to ionic liquids, where the conductivity is coupled with structural relaxation. Small-angle X-ray investigations reveal that both the intercolumnar distance and the disorder coherence length increase with alkyl chain length; conversely, the DC conductivity decreases monotonically.

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Section: Resultssupporting

confidence: 57%

Section: ■ Introductionmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Side Chain Length-Dependent Dynamics and Conductivity in Self-Assembled Ion Channels

Kolmangadi

Smales

et al. 2022

J. Phys. Chem. C

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Engineering the glass structure of a discotic liquid crystal by multiple kinetic arrests

Yu,

Chen,

Fatina

et al. 2023

The Journal of Chemical Physics

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X-ray scattering has been used to characterize the columnar packing and the π stacking in a glass-forming discotic liquid crystal. In the equilibrium liquid state, the intensities of the scattering peaks for π stacking and columnar packing are proportional to each other, indicating concurrent development of the two orders. Upon cooling into the glassy state, the π–π distance shows a kinetic arrest with a change in the thermal expansion coefficient (TEC) from 321 to 109 ppm/K, while the intercolumnar spacing exhibits a constant TEC of 113 ppm/K. By changing the cooling rate, it is possible to prepare glasses with a wide range of columnar and π stacking orders, including zero order. For each glass, the columnar order and the π stacking order correspond to a much hotter liquid than its enthalpy and π–π distance, with the difference between the two internal (fictive) temperatures exceeding 100 K. By comparison with the relaxation map obtained by dielectric spectroscopy, we find that the δ mode (disk tumbling within a column) controls the columnar order and the π stacking order trapped in the glass, while the α mode (disk spinning about its axis) controls the enthalpy and the π–π spacing. Our finding is relevant for controlling the different structural features of a molecular glass to optimize its properties.

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Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry

Cited by 2 publications

References 55 publications

Side Chain Length-Dependent Dynamics and Conductivity in Self-Assembled Ion Channels

Side Chain Length-Dependent Dynamics and Conductivity in Self-Assembled Ion Channels

Engineering the glass structure of a discotic liquid crystal by multiple kinetic arrests

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