title: Photosensitive microgels containing azobenzene surfactants of different charges.
abstract: We report on light sensitive microgel particles that can change their volume reversibly in response to illumination with light of different wavelengths. To make the anionic microgels photosensitive we add surfactants with a positively charged polyamine head group and an azobenzene containing tail. Upon illumination, azobenzene undergoes a reversible photo-isomerization reaction from a trans- to a cis-state accompanied by a change in the hydrophobicity of the surfactant. Depending on the isomerization state, the surfactant molecules are either accommodated within the microgel (trans-state) resulting in its shrinkage or desorbed back into water (cis-isomer) letting the microgel swell. We have studied three surfactants differing in the number of amino groups, so that the number of charges of the surfactant head varies between 1 and 3. We have found experimentally and theoretically that the surfactant concentration needed for microgel compaction increases with decreasing number of charges of the head group. Utilization of polyamine azobenzene containing surfactants for the light triggered remote control of the microgel size opens up a possibility for applications of light responsive microgels as drug carriers in biology and medicine.
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany. santer@uni-potsdam.de.
authors.forename: Selina
authors.initials: S
authors.lastname: Schimka
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany. santer@uni-potsdam.de.
authors.forename: Nino
authors.initials: N
authors.lastname: Lomadze
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany. santer@uni-potsdam.de.
authors.forename: Maren
authors.initials: M
authors.lastname: Rabe
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany. santer@uni-potsdam.de.
authors.forename: Alexey
authors.initials: A
authors.lastname: Kopyshev
authors.affiliation: Institute of Chemistry, Technical University Berlin, 10623 Berlin, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Lehmann
authors.affiliation: Institute of Chemistry, Technical University Berlin, 10623 Berlin, Germany.
authors.forename: Regine
authors.initials: R
authors.lastname: von Klitzing
authors.affiliation: Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
authors.forename: Artem M
authors.initials: AM
authors.lastname: Rumyantsev
authors.affiliation: Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991, Russia.
authors.forename: Elena Yu
authors.initials: EY
authors.lastname: Kramarenko
authors.affiliation: Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany. santer@uni-potsdam.de.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Santer