Surface species of nematic mixture E7 in hard confinement: spectroscopic investigations cannot distinguish among the E7 components interacting with the support surface

ABSTRACT

Properties of surface species of the nematic mixture E7 in contact with inorganic oxides (especially those containing more or less aluminium ions) are in detail investigated by infrared spectroscopy and thermogravimetry. The absorption infrared peaks were decomposed into Gaussian components, the procedure allowing an easier comparison with the behaviour of related composites. We worked at enough small concentrations of the E7 relatively to support this ratio permitting the (partial) elimination of the species belonging to the bulk. Species put here in evidence are species that are hydrogen bonded to the surface of OH groups, molecules randomly oriented on the surface, some species bonded by involvement of π electrons of the CN group to the aluminium ions, thus implying a strong interaction to the support. Supramolecular assemblies of E7 molecules are thus followed up.

GRAPHICAL ABSTRACT

KEYWORDS:

• Liquid crystals
• infrared spectroscopy
• thermogravimetry
• confinement

Acknowledgments

The authors thank the funding of the work by the Romanian Government Ministry of Research, Innovation and Digitization through National Core Founding Program (PN19-03 contract no. 21N/2019) and acknowledge the support of the PubArt project through the University Politehnica of Bucharest. Thanks are given to Prof. V. Parvulescu (University of Bucharest) for nitrogen absorption measurements.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the MINISTRY OF EDUCATION, ROMANIA Romanian Government Ministry of Research, Innovation and Digitization [PN19-03 contract no. 21N/2019].