An ab Initio CFF93 All-Atom Force Field for Polycarbonates

Sun, Huai; Mumby, Stephen J.; Maple, Jon R.; Hagler, A. T.

doi:10.1021/ja00086a030

Cited by 1,103 publications

(692 citation statements)

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“…Bulk structures of NTDA-ODADS/ODA (3/1) (see Figure 1) of molecular weight 4269.72 g/mol with sulfonic acid anions (-SO 3 -) anchored to the matrix, and water absorbed, were generated and simulated by means of the Accelrys commercial software (Materials Studio 3.2, Accelrys Inc., San Diego, CA) 53 using the PCFF91 force field. 54 The number of fixed ionic groups in the bulk structures was set equal to the IEC of the membrane, 1.87 mequiv/(g of dry polyelectrolyte). All the MD simulations were performed under NVT conditions with the working temperature of 298 K controlled by means of the Andersen thermostat method with a collision ratio of 1.0.…”

Section: Experimental Partmentioning

confidence: 99%

Simulation and Experimental Studies on Proton Diffusion in Polyelectrolytes Based on Sulfonated Naphthalenic Copolyimides

et al. 2009

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This work describes proton transport in membranes cast from dimethyl sulfoxide solutions of polyelectrolytes obtained by polycondensation of 4,4 0 -diaminodiphenyl ether (ODA) and 4,4 0 -diaminodi-phenyl ether-2,2 0 -disulfonic acid (ODADS) with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), the moles of sulfonated diamine per mole of unsulfonated one being roughly 3/1. Pulsed field gradient (PFG) NMR studies reveal two kinds of water: water located in the pores of the membranes appearing in the range 5 to 1 ppm and a minor amount of water associated with the imide groups, appearing at 1 ppm. The diffusion coefficient of 1 H in the first type of water is about 2 orders of magnitude higher than that measured in the second type and in both cases the values of this parameter severely decrease as the water content of the membranes decreases. The diffusion coefficients of bare protons, hydronium ions and water in the membranes were calculated using molecular dynamics techniques. For membranes with low water content, the diffusion coefficient of 1 H is very close to the diffusion coefficients of water and hydronium ions obtained by simulation. At high concentrations the simulated values are higher than D( 1 H). The simulated values obtained for the diffusion coefficients of hydronium ion and water for membranes equilibrated with water are fairly close to those estimated, respectively, from proton conductivity and osmotic measurements. This work suggests that the study of cationexchange membranes in the acidic form using NMR, conductivity, and molecular dynamics simulation techniques provides useful information on how structure and water content affect transport processes in membranes.

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Section: Experimental Partmentioning

confidence: 99%

Simulation and Experimental Studies on Proton Diffusion in Polyelectrolytes Based on Sulfonated Naphthalenic Copolyimides

et al. 2009

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“…Energy expressions for each of these nine networks were set up through the Discover Simulation Engine within Materials Studio 4.2 (henceforth referred to as MS Discover) using parameters from the PCFF [57] force-field 1 with non-bond terms being added using the Ewald summation technique [58]. Note that the PCFF forcefield was chosen in preference to the DREIDING force-field which was used in the earlier studies on the reflexynes [9] and the polytriangles [6] in view of the fact that unlike the PCFF force-field, the DREIDING force-field is unable to correctly represent the C 4v symmetry which is characteristic of single calix [4]arenes.…”

Section: Simulationsmentioning

confidence: 99%

On the mechanical properties and auxetic potential of various organic networked polymers

Grima

Attard

Cassar

et al. 2008

Molecular Simulation

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We simulate and analyse three types of two-dimensional networked polymers which have been predicted to exhibit on-axis auxetic behaviour (negative Poisson's ratio), namely (1) polyphenylacetylene networks that behave like flexing re-entrant honeycombs, commonly referred to as ‘reflexynes’, (2) polyphenylacetylene networks that mimic the behaviour of rotating triangles, commonly referred to as ‘polytriangles’ and (3) networked polymers built from calix[4]arene units. More specifically, we compute and compare their in-plane off-axis mechanical behaviour, in particular their off-axis Poisson's ratios and show that in some cases, the sign and magnitude of the Poisson's ratio are dependent on the direction of loading. We propose two functions that can provide a measure for the extent of auxeticity for such anisotropic materials and show that the polytriangles are predicted as the most auxetic when compared with the other networks with the reflexyne re-entrant networks being the least auxetic.peer-reviewe

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“…In particular, only the "compass" forcefield is able to provide an adequately small dispersion of the structure factor data with our statistical samples. Thus, the older polymer consistent forcefield [20], PCFF, also based in ab initio calculations, yields more negative results 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 neighboring sites [22,23]. These parameters have been set to provide results for χ (referred to the volume of a unit) similar than those expected for our realistic samples.…”

Section: Figures 2 and 3 Contain Our S(q)mentioning

confidence: 96%

Molecular dynamics simulation study of compatibility for the polyvinylmethylether/polystyrene mixture

Freire

Ahmadi

2008

Molecular Simulation

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An ab Initio CFF93 All-Atom Force Field for Polycarbonates

Cited by 1,103 publications

References 0 publications

Simulation and Experimental Studies on Proton Diffusion in Polyelectrolytes Based on Sulfonated Naphthalenic Copolyimides

Simulation and Experimental Studies on Proton Diffusion in Polyelectrolytes Based on Sulfonated Naphthalenic Copolyimides

On the mechanical properties and auxetic potential of various organic networked polymers

Molecular dynamics simulation study of compatibility for the polyvinylmethylether/polystyrene mixture

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