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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: liquid crystals;molecular dynamics;Calorimetry;Columnar mesophase;Self-assembly;self-confinement effect
Issue Date: 17-Jan-2022
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 where the molecules of HATn self-assemble and stack up in columns exhibiting one-dimensional high charge carrier mobility along the column axes. 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 phase behavior was studied by DSC 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 αcore and αalkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. Possible molecular assignments for all observed relaxation processes are proposed 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.
DOI: 10.15480/336.4096
Institute: Material- und Röntgenphysik M-2 
Document Type: Dataset
Project: Ionische Flüssigkristalle in Nanoporösen Festkörpern: Selbstorganisation, molekulare Mobilität und elektro-optische Funktionalität 
SFB 986: Maßgeschneiderte Multiskalige Materialsysteme - M3 
Funded by: Deutsche Forschungsgemeinschaft (DFG) 
More Funding information: DFG SCHO 470/21-1, SCHO 470/25-1
License: CC0 1.0 (Public Domain Dedication) CC0 1.0 (Public Domain Dedication)
Appears in Collections:Research Data TUHH

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