Publisher DOI: 10.1016/j.molliq.2022.119212
arXiv ID: 2205.02299v1
Title: Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals -- A study by broadband dielectric spectroscopy and advanced calorimetry
Language: English
Authors: Yildirim, Arda 
Krause, Christina 
Huber, Patrick  
Schönhals, Andreas 
Keywords: Physics - Soft Condensed Matter; Physics - Soft Condensed Matter; Physics - Mesoscopic Systems and Quantum Hall Effect; Physics - Materials Science;; Physics - Chemical Physics
Issue Date: 28-Apr-2022
Publisher: Elsevier
Source: Journal of Molecular Liquids 358: 119212 (2022-05-04)
Abstract (english): 
Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n=5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a γ-relaxation due to localized fluctuations as well as two glassy dynamics the α core and α alkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n=8 from a rigid constrained (n=5,6) to a softer system (n=10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition.
ISSN: 1873-3166
Institute: Material- und Röntgenphysik M-2 
Document Type: Article
Project: Ionische Flüssigkristalle in Nanoporösen Festkörpern: Selbstorganisation, molekulare Mobilität und elektro-optische Funktionalität 
SFB 986: Teilprojekt C10 - Photonische Metamaterialien mit anpassbarer und schaltbarer Anisotropie durch Funktionalisierung von porösen Festkörpern mit Flüssigkristallen 
Funded by: Deutsche Forschungsgemeinschaft (DFG) 
More Funding information: The German Science Foundation (DFG) is acknowledged for financial support (SCHO 470/21-1, SCHO 470/25-1 and Project number 430146019).
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