Engineering mesophase stability and structure via incorporation of cyclic terminal groups

Abstract

We report on the characterisation of a number of liquid-crystalline materials featuring cyclic terminal groups, which lead to significant enhancements in the temperature range of the mesomorphic state. Materials with only short terminal chains are able to support lamellar mesophase formation by appending a large terminal cyclic unit at the end of a short spacer composed of methylene units. X-ray scattering experiments reveal that the layer spacings of the lamellar smectic phase are significantly larger when a cyclic end-group is present than for equivalent linear unsubstituted materials, but there is no effect on orientational order. Fully atomistic molecular dynamics simulations faithfully reproduce experimental layer spacings and orientational order parameters, and indicate that the cyclic terminal units spontaneously segregate into diffuse sub-layers and thus cause the increased layer spacing. This shape segregation predicted by molecular dynamics simulations is observed in the crystalline solid state by X-ray diffraction.

Metadata

Authors/Creators:

Mandle, Richard J. https://orcid.org/0000-0001-9816-9661
Abbott, Laurence C. (lca100@york.ac.uk)
Fritsch, Luma
Parker, Rachel R.
Hart, Sam
Whitwood, Adrian C.
Cowling, Stephen J. https://orcid.org/0000-0002-4771-9886
Moore, John N. https://orcid.org/0000-0002-8783-5195
Goodby, John W. (jwg500@york.ac.uk)

Funding Information: The authors wish to thank the EPSRC for funding through grants EP/M020584/1 and EP/K039660/1. LF acknowledges funding by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES), finance code 001. We thank Dr Chris Rhodes of the University of York for designing and constructing the LED photoreactor used in the synthesis of compound . We thank the referees for suggestions regarding the detection of segregation effects in X-ray scattering data. Funding Information: The authors wish to thank the EPSRC for funding through grants EP/M020584/1 and EP/K039660/1. LF acknowledges funding by the Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior, Brazil (CAPES), finance code 001. We thank Dr Chris Rhodes of the University of York for designing and constructing the LED photoreactor used in the synthesis of compound 2. We thank the referees for suggestions regarding the detection of segregation effects in X-ray scattering data. Publisher Copyright: © 2022 The Royal Society of Chemistry.

Dates: