TY - JOUR A1 - Waller, Mark P. A1 - Braun, Heiko A1 - Hojdis, Nils A1 - Bühl, Michael T1 - Geometries of Second-Row Transition-Metal Complexes from Density-Functional Theory JF - Journal of Chemical Theory and Computation Y1 - 2007 U6 - http://dx.doi.org/10.1021/ct700178y SN - 1549-9626 VL - 3 IS - 6 SP - 2234 EP - 2242 ER - TY - JOUR A1 - Hentschke, Reinhard A1 - Hager, Jonathan A1 - Hojdis, Nils T1 - Molecular Modeling Approach to the Prediction of Mechanical Properties of Silica-Reinforced Rubbers JF - Journal of Applied Polymer Science N2 - Recently, we have suggested a nanomechanical model for dissipative loss in filled elastomer networks in the context of the Payne effect. The mechanism is based on a total interfiller particle force exhibiting an intermittent loop, due to the combination of short-range repulsion and dispersion forces with a long-range elastic attraction. The sum of these forces leads, under external strain, to a spontaneous instability of “bonds” between the aggregates in a filler network and attendant energy dissipation. Here, we use molecular dynamics simulations to obtain chemically realistic forces between surface modified silica particles. The latter are combined with the above model to estimate the loss modulus and the low strain storage modulus in elastomers containing the aforementioned filler-compatibilizer systems. The model is compared to experimental dynamic moduli of silica filled rubbers. We find good agreement between the model predictions and the experiments as function of the compatibilizer's molecular structure and its bulk concentration. KW - theory and modeling KW - supramolecular structures KW - rubber KW - mechanical properties KW - elastomers Y1 - 2014 U6 - http://dx.doi.org/10.1002/app.40806 SN - 1097-4628 VL - 131 IS - 18 SP - 1 EP - 9 PB - Wiley CY - New York, NY ER - TY - CHAP A1 - Breuer, Lars A1 - Raue, Markus A1 - Mang, Thomas A1 - Schöning, Michael Josef A1 - Thoelen, Ronald A1 - Wagner, Torsten T1 - Light-stimulated hydrogel actuators with incorporated graphene oxide for microfluidic applications T2 - 12. Dresdner Sensor-Symposium 2015 Y1 - 2015 U6 - http://dx.doi.org/10.5162/12dss2015/P5.8 SP - 206 EP - 209 ER - TY - BOOK A1 - Müller, Bodo A1 - Rath, Walter T1 - Formulierung von Kleb- und Dichtstoffen: das kompetente Lehrbuch für Studium und Praxis Y1 - 2015 SN - 978-3-86630-605-9 PB - Vincentz Network CY - Hannover ET - 3., vollst. überarb. Aufl. ER - TY - JOUR A1 - Hager, Jonathan A1 - Hentschke, Reinhard A1 - Hojdis, Nils A1 - Karimi-Varzaneh, Hossein Ali T1 - Computer Simulation of Particle–Particle Interaction in a Model Polymer Nanocomposite JF - Macromolecules Y1 - 2015 U6 - http://dx.doi.org/10.1021/acs.macromol.5b01864 SN - 1520-5835 VL - 48 IS - 24 SP - 9039 EP - 9049 ER - TY - JOUR A1 - Breuer, Lars A1 - Raue, Markus A1 - Strobel, M. A1 - Mang, Thomas A1 - Schöning, Michael Josef A1 - Thoelen, R. A1 - Wagner, Torsten T1 - Hydrogels with incorporated graphene oxide as light-addressable actuator materials for cell culture environments in lab-on-chip systems JF - Physica status solidi (a) N2 - Abstractauthoren Graphene oxide (GO) nanoparticles were incorporated in temperature-sensitive Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels. The nanoparticles increase the light absorption and convert light energy into heat efficiently. Thus, the hydrogels with GO can be stimulated spatially resolved by illumination as it was demonstrated by IR thermography. The temporal progression of the temperature maximum was detected for different concentrations of GO within the polymer network. Furthermore, the compatibility of PNIPAAm hydrogels with GO and cell cultures was investigated. For this purpose, culture medium was incubated with hydrogels containing GO and the viability and morphology of chinese hamster ovary (CHO) cells was examined after several days of culturing in presence of this medium. Y1 - 2016 U6 - http://dx.doi.org/10.1002/pssa.201533056 SN - 1862-6300 VL - 213 IS - 6 SP - 1520 EP - 1525 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Heinze, D. A1 - Mang, Thomas A1 - Popescu, C. A1 - Weichold, O. T1 - Effect of side chain length and degree of polymerization on the decomposition and crystallization behaviour of chlorinated poly(vinyl ester) oligomers JF - Thermochimica Acta N2 - Four members of a homologous series of chlorinated poly(vinyl ester) oligomers CCl₃–(CH₂CH (OCO(CH₂)ₘCH₃))ₙ–Cl with degrees of polymerization of 10 and 20 were prepared by telomerisation using carbon tetrachloride. The number of side chain carbon atoms ranges from 2 (poly(vinyl acetate) to 18 (poly(vinyl stearate)). The effect of the n-alkyl side chain length and of the degree of polymerization on the thermal stability and crystallization behaviour of the synthesized compounds was investigated. All oligomers degrade in two major steps by first losing HCl and side chains with subsequent breakdown of the backbone. The members with short side chains, up to poly(vinyl octanoate), are amorphous and show internal plasticization, whereas those with high number of side chain carbon atoms are semi-crystalline due to side-chain crystallization. A better packing for poly(vinyl stearate) is also noticeable. The glass transition and melting temperatures as well as the onset temperature of decomposition are influenced to a larger extent by the side chain length than by the degree of polymerization. Thermal stability is improved if both the size and number of side chains increase, but only a long side chain causes a significant increase of the resistance to degradation. This results in a stabilization of PVAc so that oligomers from poly(vinyl octanoate) on are stable under atmospheric conditions. Thus, the way to design stable, chlorinated PVEs oligomers is to use a long n-alkyl side chain. Y1 - 2016 U6 - http://dx.doi.org/10.1016/j.tca.2016.05.015 SN - 0040-6031 (electronic) VL - 637 SP - 143 EP - 153 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Svaneborg, Carsten A1 - Karimi-Varzaneh, Hossein Ali A1 - Hojdis, Nils A1 - Fleck, Franz A1 - Everaers, Ralf T1 - Multiscale approach to equilibrating model polymer melts JF - Physical Review E N2 - We present an effective and simple multiscale method for equilibrating Kremer Grest model polymer melts of varying stiffness. In our approach, we progressively equilibrate the melt structure above the tube scale, inside the tube and finally at the monomeric scale. We make use of models designed to be computationally effective at each scale. Density fluctuations in the melt structure above the tube scale are minimized through a Monte Carlo simulated annealing of a lattice polymer model. Subsequently the melt structure below the tube scale is equilibrated via the Rouse dynamics of a force-capped Kremer-Grest model that allows chains to partially interpenetrate. Finally the Kremer-Grest force field is introduced to freeze the topological state and enforce correct monomer packing. We generate 15 melts of 500 chains of 10.000 beads for varying chain stiffness as well as a number of melts with 1.000 chains of 15.000 monomers. To validate the equilibration process we study the time evolution of bulk, collective, and single-chain observables at the monomeric, mesoscopic, and macroscopic length scales. Extension of the present method to longer, branched, or polydisperse chains, and/or larger system sizes is straightforward. Y1 - 2016 U6 - http://dx.doi.org/10.1103/PhysRevE.94.032502 SN - 2470-0053 VL - 94 IS - 032502 PB - AIP Publishing CY - Melville, NY ER - TY - JOUR A1 - Schwab, Lukas A1 - Hojdis, Nils A1 - Lacayo, Jorge A1 - Wilhelm, Manfred T1 - Fourier-Transform Rheology of Unvulcanized, Carbon Black Filled Styrene Butadiene Rubber JF - Macromolecular Materials and Engineering N2 - Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ0 < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ0 = 0.32). The addition of up to 70 phr CB leads to an increase of I3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I3/1 is pronounced for CB levels above the percolation threshold. Y1 - 2016 U6 - http://dx.doi.org/10.1002/mame.201500356 SN - 1439-2054 VL - 301 IS - 4 SP - 457 EP - 468 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Harish, Ajay B. A1 - Wriggers, Peter A1 - Jungk, Juliane A1 - Hojdis, Nils A1 - Recker, Carla T1 - Mesoscale Constitutive Modeling of Non-Crystallizing Filled Elastomers JF - Computational Mechanics N2 - Elastomers are exceptional materials owing to their ability to undergo large deformations before failure. However, due to their very low stiffness, they are not always suitable for industrial applications. Addition of filler particles provides reinforcing effects and thus enhances the material properties that render them more versatile for applications like tyres etc. However, deformation behavior of filled polymers is accompanied by several nonlinear effects like Mullins and Payne effect. To this day, the physical and chemical changes resulting in such nonlinear effect remain an active area of research. In this work, we develop a heterogeneous (or multiphase) constitutive model at the mesoscale explicitly considering filler particle aggregates, elastomeric matrix and their mechanical interaction through an approximate interface layer. The developed constitutive model is used to demonstrate cluster breakage, also, as one of the possible sources for Mullins effect observed in non-crystallizing filled elastomers. Y1 - 2016 U6 - http://dx.doi.org/10.1007/s00466-015-1251-1 SN - 1432-0924 VL - 57 SP - 653 EP - 677 PB - Springer CY - Berlin ER -