@phdthesis{Berdzinski2014,
  author    = {Berdzinski, Stefan},
  title     = {Photoinduzierte radikalische Polymerisation in ionischen Fl{\"u}ssigkeiten und der Einfluss der Radikalrekombination},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-72582},
  school      = {Universit{\"a}t Potsdam},
  pages     = {VIII, 114},
  year      = {2014},
  abstract  = {Die vorliegende Arbeit behandelt Untersuchungen zum Einfluss ionischer Fl{\"u}ssigkeiten sowohl auf den Rekombinationsprozess photolytisch generierter Lophylradikale als auch auf die photoinduzierte Polymerisation. Im Fokus standen hierbei pyrrolidiniumbasierte ionische Fl{\"u}ssigkeiten sowie polymerisierbare imidazoliumbasierte ionische Fl{\"u}ssigkeiten. Mittels UV-Vis-Spektroskopie wurde in den ionischen Fl{\"u}ssigkeiten im Vergleich zu ausgew{\"a}hlten organischen L{\"o}sungsmitteln die Rekombinationskinetik der aus o-Cl-HABI photolytisch generierten Lophylradikale bei unterschiedlichen Temperaturen verfolgt und die Geschwindigkeitskonstanten der Radikalrekombination bestimmt. Die Charakterisierung des Rekombinationsprozesses erfolgt dabei insbesondere unter Verwendung der mittels Eyring-Gleichung ermittelten Aktivierungsparameter. Hierbei konnte gezeigt werden, dass die Rekombination der Lophylradikale in den ionischen Fl{\"u}ssigkeiten im Gegensatz zu den organischen L{\"o}sungsmitteln zu einem großen Anteil innerhalb des L{\"o}sungsmittelk{\"a}figs erfolgt. Weiterhin wurden f{\"u}r den Einsatz von o-Cl-HABI als Radikalbildner in den photoinduzierten Polymerisationen mehrere m{\"o}gliche Co-Initiatoren {\"u}ber photokalorimetrische Messungen untersucht. Hierbei wurde auch ein neuer Aspekt zur Ketten{\"u}bertragung vom Lophylradikal auf den heterocyclischen Co-Initiator vorgestellt. Dar{\"u}ber hinaus wurden photoinduzierte Polymerisationen unter Einsatz eines Initiatorsystems, bestehend aus o-Cl-HABI als Radikalbildner und einem heterocyclischen Co-Initiator, in den ionischen Fl{\"u}ssigkeiten untersucht. Diese Untersuchungen beinhalten zum einen photokalorimetrische Messungen der photoinduzierten Polymerisation von polymerisierbaren imidazoliumbasierten ionischen Fl{\"u}ssigkeiten. Zum anderen wurden Untersuchungen zur photoinduzierten Polymerisation von Methylmethacrylat in pyrrolidiniumbasierten ionischen Fl{\"u}ssigkeiten durchgef{\"u}hrt. Dabei wurden Einflussparameter wie Zeit, Temperatur, Viskosit{\"a}t, L{\"o}sungsmittelk{\"a}figeffekt und die Alkylkettenl{\"a}nge am Kation der ionischen Fl{\"u}ssigkeiten auf die Ausbeuten und Molmassen sowie Molmassenverteilungen der Polymere hin untersucht.},
  language  = {de}
}
@article{SangoroIacobAgapovetal.2014,
  author    = {Sangoro, Joshia R. and Iacob, C. and Agapov, A. L. and Wang, Yangyang and Berdzinski, Stefan and Rexhausen, Hans and Strehmel, Veronika and Friedrich, C. and Sokolov, A. P. and Kremer, F.},
  title     = {Decoupling of ionic conductivity from structural dynamics in polymerized ionic liquids},
  series = {Soft matter},
  volume    = {10},
  journal   = {Soft matter},
  number    = {20},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1744-683X},
  doi       = {10.1039/c3sm53202j},
  pages     = {3536 -- 3540},
  year      = {2014},
  abstract  = {Charge transport and structural dynamics in low molecular weight and polymerized 1-vinyl-3-pentylimidazolium bis(trifluoromethylsulfonyl) imide ionic liquids (ILs) are investigated by a combination of broadband dielectric spectroscopy, dynamic mechanical spectroscopy and differential scanning calorimetry. While the dc conductivity and fluidity exhibit practically identical temperature dependence for the non-polymerized IL, a significant decoupling of ionic conduction from structural dynamics is observed for the polymerized IL. In addition, the dc conductivity of the polymerized IL exceeds that of its molecular counterpart by four orders of magnitude at their respective calorimetric glass transition temperatures. This is attributed to the unusually high mobility of the anions especially at lower temperatures when the structural dynamics is significantly slowed down. A simple physical explanation of the possible origin of the remarkable decoupling of ionic conductivity from structural dynamics is proposed.},
  language  = {en}
}
@article{StrehmelBerdzinskiStrauchetal.2014,
  author    = {Strehmel, Veronika and Berdzinski, Stefan and Strauch, Peter and Hoffmann-Jacobsen, Kerstin and Strehmel, Bernd},
  title     = {Investigation of molecular solvents and ionic liquids with a dual probe},
  series = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics},
  volume    = {228},
  journal   = {Zeitschrift f{\"u}r physikalische Chemie : international journal of research in physical chemistry and chemical physics},
  number    = {2-3},
  publisher = {De Gruyter},
  address   = {Berlin},
  issn      = {0942-9352},
  doi       = {10.1515/zpch-2014-0453},
  pages     = {155 -- 169},
  year      = {2014},
  abstract  = {A dual probe was investigated by UV-Vis, fluorescence, and ESR spectroscopy. It comprises the pyrene chromophore and the paramagnetic 2,2,6,6-tetramethylpiperidinyl-N-oxyl radical that are covalently linked together via an ester bridge. The dual probe was used to investigate molecular solvents of different polarity as well as ionic liquids bearing either imidazolium or pyrrolidinium cations and various anions, such as bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, tris(pentafluoroethyl)trifluorophosphate, or dicyanamide. The dual probe does not show solvatochromism that is typical for some pyrenes. Furthermore, the dual probe is considerable less mobile compared to 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) without additional substituent as detected by ESR spectroscopy. This is caused by the bulky pyrenyl substituent bound at the dual probe resulting in a reduced mobility of the dual probe.},
  language  = {en}
}
@article{StrehmelBerdzinskiRexhausen2014,
  author    = {Strehmel, Veronika and Berdzinski, Stefan and Rexhausen, Hans},
  title     = {Interactions between ionic liquids and radicals},
  series = {Journal of molecular liquids},
  volume    = {192},
  journal   = {Journal of molecular liquids},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0167-7322},
  doi       = {10.1016/j.molliq.2013.12.007},
  pages     = {153 -- 170},
  year      = {2014},
  abstract  = {Ionic liquids were investigated with both stable radicals on the basis of 2,2,6,6-tetramethylpiperidine-1-yloxyl (TEMPO) and photogenerated lophyl radicals. The ionic liquids are composed either of bis(trifluoromethylsulfonyl)imide (NTf2) as anion and various cations or they contain an imidazolium ion in combination with various anions. The cations include imidazolium, pyrrolidinium, piperidinium, polymethine or ammonium ions. Furthermore, BF4-, PF6-, triflate, camphorsulfonate, lactate, tosylate or tris(pentafluoroethyl) trifluorophosphate (FAP) are the counter ions in the imidazolium salts. The structural variation of the ionic liquids results in differences in glass formation, semiaystallinity, or crystallinity, as well as in viscosity differences. Furthermore, a vinyl substituent at the imidazolium ion and a methacryloyloxyethyl substituent at the ammonium ion result in polymerizable ionic liquids that were converted via a radical mechanism in amorphous polymerized ionic liquids with a glass transition temperature, which is significantly higher compared to the ionic liquids. An additional substituent at TEMPO causes additional hydrogen bond formation or additional Coulomb interactions with the individual ions of the ionic liquids compared to TEMPO. This influences the mobility of these radicals in the ionic liquid expressed by differences in the average rotational correlation time (T-rot). The mobility of the radicals in the ionic liquids as function of the temperature describes ionic liquids either as continuum in analogy to molecular solvents using the Stokes-Einstein model, that is the case for 1-butyl-3-methylimidazolium NTf2, or as medium where free volume effects are important for the mobility of a solute in the ionic liquid using the model of Spernol, Gierer, and Wirtz. The 1-butyl-3-methylimidazolium BF4- fits well into the latter. Furthermore, the isotropic hyperfine coupling constant (A(iso)(N-14)) of the stable radicals gives information about micropolarity of the ionic liquids only if the mobility of the radical is high enough in the ionic liquid. In addition to the rotational mobility of the stable radicals, the photogenerated lophyl radicals give information about translational diffusion of radicals and solvent cage effects in the ionic liquids. The application of the Eyring equation results mostly in the expected negative values of the activation entropy for the transition state that is typical for bimolecular reactions. Only few examples show a less negative or positive activation entropy for the bimolecular reaction, which may be attributed to radical recombination within the solvent cage to a high extent. The results obtained during investigation of radicals in ionic liquids are important to understand the radical processes in ionic liquids that may occur for example in dye sensitized solar cells, photo or thermally induced reactions or radical polymerizations in ionic liquids.},
  language  = {en}
}