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Nikitin A.N.,Institute on Laser and Information Technologies | Hutchinson R.A.,Queens University | Buback M.,University of Gottingen | Hesse P.,University of Gottingen
Macromolecular Chemistry and Physics | Year: 2011

Pulsed laser polymerization (PLP) with subsequent analysis of molecular mass distribution (MMD) is used to determine the rate coefficient of chain transfer to an agent A, ktrA, by varying pulse repetition rate such that the contributions of PLP-induced and chain-transfer-induced peaks to the MMD change to a significant extent. It is shown by simulation that the relative heights of these peaks may be used to estimate ktrA. The method is applied to evaluation of the rate coefficient of chain transfer to dodecyl mercaptan with butyl methacrylate polymerizations at -11, 0, 20 and 40°C. The Arrhenius parameters for this coefficient are determined to be: A(k trA) = (2.2 ± 0.6) × 106 L · mol -1 · s-1 and Ea(ktrA) = (22.1 ± 0.7) kJ · mol-1.(Figure Presented) © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Nazarov M.M.,Institute on Laser and Information Technologies | Shkurinov A.P.,Moscow State University | Garet F.,University of Savoy | Coutaz J.-L.,University of Savoy
IEEE Transactions on Terahertz Science and Technology | Year: 2015

We excite surface plasmons (SPs) at the surface of highly doped Si using a prism coupler, and we study the propagation properties of these SPs in order to characterize the terahertz (THz) response of the doped semiconductor. Thanks to the long interaction length of the propagating SP with the substrate material, the method is more sensitive than classical THz time-domain spectroscopy in reflection or in transmission. Moreover, we propose a new technique based on measuring the SP signal, for which the delicate problem of accurately measuring the phase of the signal is solved. All of these different experiment techniques allow us to determine reliably the dielectric function of highly doped Si in the THz range. It appears that the experimentally determined values differ strongly from the ones calculated with a Drude model. © 2011-2012 IEEE.


Nikitin A.N.,Institute on Laser and Information Technologies | Hutchinson R.A.,Queens University | Hesse P.,University of Gottingen | Hesse P.,BASF
Macromolecular Chemistry and Physics | Year: 2013

The pulsed laser polymerization-high termination rate limit-size-exclusion chromatography (PLP-HTRL-SEC) technique is used to estimate the mode of termination (δ) for n-butyl methacrylate (n-BMA) polymerization at 30 °C. It is found that molecular mass distributions measured in these experiments are influenced by an unknown side reaction such as retardation or chain transfer that results in a marked decrease of intensity of the PLP peak. A new approach is developed to evaluate δ, with numerical experiments used to demonstrate the robustness of the methodology in the presence of retardation or chain transfer to agent. Application to the experimental n-BMA polymerization at 30 °C leads to an estimate for δ of 0.60 ± 0.03. The pulsed laser polymerization-high termination rate limit-size-exclusion chromatography (PLP-HTRL-SEC) method is extended to estimate the mode of termination (δ) even in the presence of side reactions such as retardation or chain transfer to agent. By applying this method for n-BMA polymerization at 30 °C, δ is estimated to be 0.60 ± 0.03. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Nikitin A.N.,Free University of Berlin | Nikitin A.N.,Institute on Laser and Information Technologies | Wulkow M.,CiT GmbH | Schutte C.,Free University of Berlin
Macromolecular Theory and Simulations | Year: 2013

The modeling approach called "numerical fractionation" has been incorporated into a PREDICI model to simulate crosslinking copolymerization. In order to take inhomogeneities of the considered copolymerization into account, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain-length dependence of the termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m-divinylbenzene crosslinking copolymerization at low crosslinker content has been simulated. The chain-length dependence of the termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for a correct description of the gel points. The modeling approach called "numerical fractionation" has been incorporated into a PREDICI model to simulate crosslinking copolymerization. The kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. The styrene/m-divinylbenzene copolymerization at low content of the crosslinker is simulated. The chain-length dependence of the termination is found to accelerate the gel point in monovinyl/divinyl copolymerization. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kosarev I.N.,Institute on Laser and Information Technologies
Physics of Plasmas | Year: 2015

Interaction of femtosecond laser pulses with the intensities 1021, 1022W/cm2 with CH plastic foils is studied in the framework of kinetic theory of laser plasma based on the construction of propagators (in classical limit) for electron and ion distribution functions in plasmas. The calculations have been performed for real densities and charges of plasma ions. Protons are accelerated both in the direction of laser pulse (up to 1 GeV) and in the opposite direction (more than 5 GeV). The mechanisms of forward acceleration are different for various intensities. © 2015 AIP Publishing LLC.

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