A Coarse-Grained Model for Polyethylene Oxide and Polyethylene Glycol: Conformation and Hydrodynamics

Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
The Journal of Physical Chemistry B (Impact Factor: 3.3). 09/2009; 113(40):13186-94. DOI: 10.1021/jp9058966
Source: PubMed


A coarse-grained (CG) model for polyethylene oxide (PEO) and polyethylene glycol (PEG) developed within the framework of the MARTINI CG force field (FF) using the distributions of bonds, angles, and dihedrals from the CHARMM all-atom FF is presented. Densities of neat low molecular weight PEO agree with experiment, and the radius of gyration R(g) = 19.1 A +/- 0.7 for 76-mers of PEO (M(w) approximately 3400), in excellent agreement with neutron scattering results for an equal sized PEG. Simulations of 9, 18, 27, 36, 44, 67, 76, 90, 112, 135, and 158-mers of the CG PEO (442 < M(w) < 6998) at low concentration in water show the experimentally observed transition from ideal chain to real chain behavior at 1600 < M(w) < 2000, in excellent agreement with the dependence of experimentally observed hydrodynamic radii of PEG. Hydrodynamic radii of PEO calculated from diffusion coefficients of the higher M(w) PEO also agree well with experiment. R(g) calculated from both all-atom and CG simulations of PEO76 at 21 and 148 mg/cm(3) are found to be nearly equal. This lack of concentration dependence implies that apparent R(g) from scattering experiments at high concentration should not be taken to be the chain dimension. Simulations of PEO grafted to a nonadsorbing surface yield a mushroom to brush transition that is well described by the Alexander-de Gennes formalism.

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Available from: Siewert J Marrink, Feb 03, 2014
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    • "In order to study F127, and other co-polymers, we have mapped each monomer, EO and PO, as a single CG bead (schematized in Fig. 1B), considering their oxygen atom as the center of each bead. For the EO CG beads we have used the parameters set developed by Lee et al. [30] [31], which have been incorporated to the MFF. These parameters were developed based on atomistic simulations and experimental results. "
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    • "Over the last years, the application of coarse-grained MARTINI models [1] [2] [3] [4] for the simulation of various systems has emerged rapidly . While originally intended to study the behavior of lipid bilayers [1], recent developments also include molecular topologies and force fields for DNA, proteins and polymers [3] [4] [5] [6] [7]. The success of the MARTINI force field becomes reasonable with regard to the broad range of applicability and the significant acceleration of simulation time by the introduction of an efficient coarse-graining scheme [4]. "
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    • "When grafting distance is larger than the chain length, end-grafted PE chains show a ''mushroom'' configuration. Otherwise, they stay in a ''brush'' configuration [38]. As discussed above, aligned endgrafted PE chains (brush configuration) can lead to better interfacial thermal conductance than that of random morphology . "
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