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  • 1.
    Bergenudd, Helena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Predicting the Limit of Control in the ATRP Process: Results from Kinetic Simulations2011Ingår i: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, Vol. 20, nr 9, s. 814-825Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kinetic simulations are reported, where the ATRP equilibrium constant K(ATRP) is varied and the rates and degree of control in different ATRP systems are evaluated. The apparent rate constant k(app) increases with increasing K(ATRP), but a maximum is reached. The limit of control is passed before the maximum, i.e. when K(ATRP) is increased further, apparent first-order kinetics and well-controlled molecular weights will no longer be obtained. The equilibrium constant at which the limit of control is reached varies linearly with the propagation rate constant. This enables the design of well controlled ATRP systems. The influence of the conversion and chain length dependence of the termination rate constant on the simulation results is discussed.

  • 2.
    Dahlgren, Björn
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Sabatino, Maria Antonietta
    Univ Palermo, Dipartimento Ingn, Viale Sci 6, I-90128 Palermo, Italy..
    Dispenza, Clelia
    Univ Palermo, Dipartimento Ingn, Viale Sci 6, I-90128 Palermo, Italy.;CNR, Ist Biofis IBF, Via U La Malfa 153, I-90146 Palermo, Italy..
    Jonsson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Numerical Simulations of Nanogel Synthesis Using Pulsed Electron Beam2019Ingår i: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, artikel-id 1900046Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a new method for numerical simulation of the radiation chemistry of aqueous polymer solutions exposed to a sequence of electron pulses is presented. The numerical simulations are based on a deterministic approach encompassing the conventional homogeneous radiation chemistry of water as well as the chemistry of polymer radicals. The multitude of possible reactions in the macromolecular system is handled by allowing for a large number of macromolecular species. The speciation of macromolecular species is done to account for variations in molecular weight, number of alkyl radicals per chain, number of peroxyl radicals per chain, number of oxyl radicals per chain, and number of internal loops. As benchmarking, previously published results from a series of experiments on pulsed irradiation of aqueous poly(N-vinylpyrrolidone) (PVP) solutions are used. The numerical simulations clearly show that the pulsed nature of the radiation must be accounted for. The simulations qualitatively reproduce the experimentally observed impact of initial gas saturation (air and N2O) and polymer concentration on the molecular chain length upon irradiation. The formation of double bonds as a function of dose as well as the impact of effective dose rate on the final chain length are also qualitatively reproduced in the simulations.

  • 3.
    Yang, Guanda
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.
    Nilsson, Fritjof
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Schubert, Dirk W.
    A Study of Finite Size Effects and Periodic Boundary Conditions to Simulations of a Novel Theoretical Self-Consistent Mean-Field Approach2019Ingår i: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, artikel-id 1900023Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a previous work, a very promising mathematical model for predicting the electrical conductivity below the electrical percolation threshold, for both isotropic and anisotropic composites, was published by Schubert. In this work, periodic boundary condition of the simulation is utilized. The results are also compared to the previous work and other theoretical models. The truncated fibers due to finite size of the simulation volume are considered as two individual pieces so that the real aspect ratios will also be taken into consideration. A comparison is made between two groups, in which the length and the radius of the carbon fibers are changed, respectively, under certain aspect ratios. With three different sizes of the simulation volumes, the influence on the results due to the finite size effect is calculated.

  • 4.
    Yang, Guanda
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Qu, Muchao
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Nilsson, Fritjof
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Novel Theoretical Self-Consistent Mean-Field Approach to Describe the Conductivity of Carbon Fiber-Filled Thermoplastics: PART II. Validation by Computer Simulation2018Ingår i: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, Vol. 27, nr 4, artikel-id 1700105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrical conductivity of polymeric fiber composites is generally strongly dependent on the constituent conductivities, the fiber filler fraction, the fiber aspect ratio, and on the orientation of the fibers. Even though electrically conductive polymer composites are emerging materials of high scientific and commercial interest, accurate mathematical models for describing such materials are rare. A very promising mathematical model for predicting the electrical conductivity below the electrical percolation threshold, for both isotropic and anisotropic composites, is however recently published by Schubert. The shortcomings of that study are that the model includes so far only one predicted parameter and that it is not sufficiently validated. In the current study, finite element modeling is used to successfully validate the model of Schubert for isotropic fiber composites and to accurately determine the predicted parameter. These theoretical predictions are finally compared with experimental conductivity data for isotropic carbon fiber/poly(methyl methacrylate) (PMMA) composites with fiber filler fractions in the range 0-12 vol% and fiber aspect ratios from 5 to 30. The model forecasts, without any adjustable parameters, are satisfactory close to the experimental data.

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