Photoisomerization induced scission of rod-like micelles unravelled with multiscale modeling

Gabriel Heerdt; Ionut Tranca; Albert J Markvoort; Bartłomiej M Szyja; Nelson H Morgon; Emiel J M Hensen

doi:10.1016/j.jcis.2017.09.036

Photoisomerization induced scission of rod-like micelles unravelled with multiscale modeling

J Colloid Interface Sci. 2018 Jan 15:510:357-367. doi: 10.1016/j.jcis.2017.09.036. Epub 2017 Sep 12.

Authors

Gabriel Heerdt¹, Ionut Tranca², Albert J Markvoort³, Bartłomiej M Szyja⁴, Nelson H Morgon⁵, Emiel J M Hensen⁶

Affiliations

¹ Department of Physical-Chemistry, Institute of Chemistry, University of Campinas, Barão Geraldo, P.O. Box 6154, 13083-970 Campinas, São Paulo, Brazil. Electronic address: gabheerdt@gmail.com.
² Laboratory of Inorganic Materials Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. Electronic address: i.tranca@fz-juelich.de.
³ Computational Biology Group, Department of Biomedical Engineering, and Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, The Netherlands. Electronic address: A.J.Markvoort@tue.nl.
⁴ Division of Fuels Chemistry and Technology, Faculty of Chemistry, Wrocław University of Science and Technology, Gdańska 7/9, 50-344 Wrocław, Poland. Electronic address: b.m.szyja@pwr.edu.pl.
⁵ Department of Physical-Chemistry, Institute of Chemistry, University of Campinas, Barão Geraldo, P.O. Box 6154, 13083-970 Campinas, São Paulo, Brazil. Electronic address: morgon@iqm.unicamp.br.
⁶ Laboratory of Inorganic Materials Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. Electronic address: e.j.m.hensen@tue.nl.

PMID: 28961434
DOI: 10.1016/j.jcis.2017.09.036

Abstract

Hypothesis: In photorheological fluids, subtle molecular changes caused by light lead to abrupt macroscopic alterations. Upon UV irradiation of an aqueous cetyltrimethylammonium bromide (CTAB) and trans-ortho-methoxycinnamic acid (trans-OMCA) solution, for instance, the viscosity drops over orders of magnitude. Multiscale modeling allows to elucidate the mechanisms behind these photorheological effects.

Experiments: We use time-dependent DFT calculations to study the photoisomerization, and a combination of atomistic molecular dynamics (MD) and DFT to probe the influence of both OMCA isomers on the micellar solutions.

Findings: The time-dependent DFT calculations show that the isomerization pathway occurs in the first triplet excited state with a minimum energy conformation closest to the after photoisomerization predominant cis configuration. In the MD simulations, with sub-microsecond timescales much shorter than the experimental morphological transition, already a clear difference is observed in the packing of the two OMCA isomers: contrary to trans-OMCA, cis-OMCA exposes notable part of its hydrophobic aromatic rings at the micelle surface. This can explain why trans-OMCA adopts rod-like micellar packing (high viscosity) while cis-OMCA spherical micellar packing (low viscosity). Moreover, lowering of the OMCA co-solute concentration allowed us to perform full simulation of the breakup process of the rod-like micelles which are stable prior to isomerization.

Keywords: MD simulations; Micelle transition; Photorheology; Rotational barriers; Time-dependent DFT.