60045
2021
2021
eng
866
875
10
586
article
Elsevier
San Diego
1
2020-10-20
2021-03-15
--
Quantification of ordering in active light driven colloids
Hypothesis:
Light driven diffusioosmosis allows for the controlled self-assembly of colloidal particles. Illuminating of colloidal suspensions built of nanoporous silica microspheres dispersed in aqueous solution containing photosensitive azobenzene cationic surfactant enables manufacturing self-assembled well-ordered 2D colloidal patterns. We conjectured that ordering in this patterns may be quantified with the Voronoi entropy.
Experiments:
Depending on the isomerization state the surfactant either tends to absorb (trans-state) into negatively charged pores or diffuse out (cis-isomer) of the particles generating an excess concentration near the colloids outer surface and thus resulting in the initiation of diffusioosmotic flow. The direction of the flow can be controlled by the wavelength and intensity of irradiation. Under irradiations with blue light the colloids separate within a few seconds forming equidistant particle ensemble where long range diffusioosmotic repulsion acts over distances exceeding several times the particle diameter. Hierarchy of ordering in the studied colloidal systems is distinguished, namely: i) ordering of individual separated colloidal particles; ii) ordering of clusters built of colloidal particles; iii) ordering within clusters of individual colloidal particles.
Findings:
The study of the temporal change in the Voronoi entropy for the light illuminated colloidal dispersions allowed quantification of ordering evolution on different lateral scales and under different irradiation conditions. Fourier analysis of the time evolution of the Voronoi entropy is presented. Fourier spectrum of the "small-area" (100 x 100 mu m) reveals the pronounced peak at f = 1.125 Hz reflecting the oscillations of individual particles at this frequency. Ordering in hierarchical colloidal system emerging on different lateral scales is addressed. The minimal Voronoi entropy is intrinsic for the close packed 2D clusters. (C) 2020 Published by Elsevier Inc.
Journal of colloid and interface science
10.1016/j.jcis.2020.10.053
33127053
0021-9797
1095-7103
outputup:dataSource:PubMed:2021
WOS:000606774800005
Santer, S (corresponding author), Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany.; Bormashenko, E (corresponding author), Ariel Univ, Dept Chem Engn, Fac Engn, POB 3, IL-40700 Ariel, Israel., edward@ariel.ac.il; santer@uni-potsdam.de
Priority Program 1726 "Microswimmers-From Single Particle Motion to Collective Behaviour", Germany; DFG German Research Foundation (DFG) European Commission [SA1657/8-1]; Russian Science FoundationRussian Science Foundation (RSF) [19-19-00076]
Bormashenko, Edvard
Santer, Svetlana
2023-07-20T04:21:23+00:00
sword
importub
filename=package.tar
97f442195d7ad36f8d5603a464eb9773
241597-5
1469021-4
false
true
Mark Frenkel
Pooja Arya
Edṿard Bormashenḳo
Svetlana A. Santer
eng
uncontrolled
Azobenzene containing cationic surfactants
eng
uncontrolled
Light induced diffusioosmotic flow
eng
uncontrolled
2D colloid ordering
eng
uncontrolled
Voronoi entropy
Chemie und zugeordnete Wissenschaften
Institut für Physik und Astronomie
Referiert
Import
38442
2015
2015
eng
65
72
8
79
article
Elsevier
Oxford
1
--
--
--
Making polymer brush photosensitive with azobenzene containing surfactants
We report on rendering polyelectrolyte brushes photosensitive by loading them with azobenzene-containing cationic surfactants. Planar poly( methacrylic acid) (PMAA) brushes are synthesized using the "grafting from" free-radical polymerization scheme followed by exposure to a solution of photosensitive surfactants consisting of positively-charged head groups and hydrophobic tails into which azobenzene moieties are inserted. In this study the length of the hydrophobic methylene spacer connecting the azobenzene and the charged head group ranges from 4 to 10 CH2 groups. Under irradiation with UV light, the photo-isomerization of azobenzene integrated into a surfactant results in a change in size, geometry, dipole moment and free volume of the whole molecule. When the brush loaded with photosensitive surfactants is exposed to irradiation with UV interference patterns, the topography of the brush deforms following the distribution of the light intensity, exhibiting surface relief gratings (SRG). Since SRG formation is accompanied by a local rupturing of polymer chains in areas from which the polymer material is receding, most of the polymer material is removed from the surface during treatment with good solvent, leaving behind characteristic patterns of lines or dots. The azobenzene molecules still integrated within the polymer film can be removed by washing the brush with water. The remaining nano-structured brush can then be re-used for further functionalization. Although the opto-mechanically induced rupturing occurs for all surfactants, larger species do not penetrate deep enough into the brush such that after rupturing a leftover layer of polymer material remains on the substrate. This indicates that rupturing occurs predominantly in regions of high surfactant density.
Polymer : the international journal for the science and technology of polymers
10.1016/j.polymer.2015.09.023
0032-3861
1873-2291
wos:2015
WOS:000365042500008
Santer, S (reprint author), Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany., santer@uni-potsdam.de
VolkswagenStiftung, Germany; DFG [SA1657/8-1]; International Max Plan
Research Graduate School on Multiscale Bio-systems (Potsdam, Germany);
Helmholtz Graduate School on Macromolecular Bioscience (Teltow,
Germany); National Science Foundation [DMR-1404639]
Alexey Kopyshev
Nino Lomadze
David Feldmann
Jan Genzer
Svetlana A. Santer
eng
uncontrolled
Azobenzene containing cationic surfactants
eng
uncontrolled
Photosensitive polymer brushes
eng
uncontrolled
Opto-mechanically induced scission of
eng
uncontrolled
polymer chains
Institut für Biochemie und Biologie
Referiert
9424
2015
2015
eng
65
72
79
article
Elsevier Science
Oxford
1
--
2015-11-19
--
Making polymer brush photosensitive with azobenzene containing surfactants
We report on rendering polyelectrolyte brushes photosensitive by loading them with azobenzene-containing cationic surfactants. Planar poly(methacrylic acid) (PMAA) brushes are synthesized using the “grafting from” free-radical polymerization scheme followed by exposure to a solution of photosensitive surfactants consisting of positively-charged head groups and hydrophobic tails into which azobenzene moieties are inserted. In this study the length of the hydrophobic methylene spacer connecting the azobenzene and the charged head group ranges from 4 to 10 CH2 groups. Under irradiation with UV light, the photo-isomerization of azobenzene integrated into a surfactant results in a change in size, geometry, dipole moment and free volume of the whole molecule. When the brush loaded with photosensitive surfactants is exposed to irradiation with UV interference patterns, the topography of the brush deforms following the distribution of the light intensity, exhibiting surface relief gratings (SRG). Since SRG formation is accompanied by a local rupturing of polymer chains in areas from which the polymer material is receding, most of the polymer material is removed from the surface during treatment with good solvent, leaving behind characteristic patterns of lines or dots. The azobenzene molecules still integrated within the polymer film can be removed by washing the brush with water. The remaining nano-structured brush can then be re-used for further functionalization. Although the opto-mechanically induced rupturing occurs for all surfactants, larger species do not penetrate deep enough into the brush such that after rupturing a leftover layer of polymer material remains on the substrate. This indicates that rupturing occurs predominantly in regions of high surfactant density.
Polymer : the international journal for the science and technology of polymers
10.1016/j.polymer.2015.09.023
0032-3861
online registration
Keine öffentliche Lizenz: Unter Urheberrechtsschutz
Alexey Kopyshev
Nino Lomadze
David Feldman
Jan Genzer
Svetlana A. Santer
eng
uncontrolled
Azobenzene containing cationic surfactants
eng
uncontrolled
Photosensitive polymer brushes
eng
uncontrolled
Opto-mechanically induced scission of polymer chains
Biowissenschaften; Biologie
Institut für Physik und Astronomie
Referiert
Universität Potsdam