On the effects of different trans and cis populations in azobenzene liquid crystal elastomers: a Monte Carlo investigation

Skačej, Gregor (author), Querciagrossa, Lara (author), Zannoni, Claudio (author)

We investigate main-chain liquid crystal elastomers (LCEs) formed by photoresponsive azobenzene units with different populations of trans and cis conformers (from fully trans to fully cis). We study their macroscopic properties as well as their molecular organization using extensive Monte Carlo simulations of a simple coarse-grained model where the trans and cis conformers are represented by soft-core biaxial Gay−Berne particles with size and interaction energy parameters obtained by fitting a bare bone azobenzene moiety represented at atomistic level. We find that increasing the fraction of cis conformers, as could be obtained by near-UV irradiation, shifts the nematic−isotropic transition to a lower temperature, consistently with experiment, while generating internal stress in a clamped sample. An analysis of pair distributions shows that the immediate surroundings of a bent cis molecule are slightly less dense and more orientationally disordered in comparison with that of a trans conformer. Comparing nematic and smectic LCEs, actuation in the smectic phase proved less effective, disrupting the smectic layers to some extent but preserving orientational order of the azobenzene moieties.

• Language: English
• Keywords: liquid crystal elastomers, azobenzene, physical chemistry, actuation, Gay−Berne potential, Monte Carlo simulations, liquid chromatography, molecular structure, order, stress
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2023
• Number of pages: Str. 5805−5815
• Numbering: Vol. 5, iss. 8
• PID: 20.500.12556/RUL-152671
• UDC: 544.25
• ISSN on article: 2637-6105
• DOI: 10.1021/acsapm.3c00361
• COBISS.SI-ID: 160768771
• Publication date in RUL: 04.12.2023

Record is a part of a journal

• Title: ACS applied polymer materials
• Publisher: American Chemical Society
• ISSN: 2637-6105
• COBISS.SI-ID: 22011414

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: tekočekristalni elastomeri, azobenzen, fizikalna kemija