Detailed Atomistic Molecular Dynamics Simulation of cis-1,4-Poly(butadiene)

Abstract

Well-relaxed atomistic configurations of model cis-1,4-poly(butadiene) (PB) systems, ranging in molecular length from C 32 to C400, have been subjected to detailed molecular dynamics simulations in the NPT ensemble for times up to 600 ns. Results are presented for the static and (mainly) dynamic properties of these systems, such as the segmental and terminal relaxation properties, the self-diffusion coefficient, D, and the single-chain dynamic structure factor, S(q,t), at pressure P ) 1 atm and temperatures, T, between 298 and 430 K. Our simulation data demonstrate that, around C 200, D is seen to exhibit a change in its power-law dependence on molecular weight, M, deviating from a Rouse (where D ≈ M -b with b = 1) toward a reptation-like (where D ≈ M -b with b = 2.1) behavior. Following the methodology introduced by Harmandaris et al. [Macromolecules 2003[Macromolecules , 36, 1376 for linear polyethylene (PE) melts, we have further been able to successfully project atomistic cis-1,4-PB chain configurations to primitive paths, thereby mapping simulation trajectories onto the reptation model. This has allowed us to consistently calculate the friction coefficient, , per carbon atom of cis-1,4-PB melts both below and above the molecular weight for the formation of entanglements. The dependence of D on T is also presented.

Molecular dynamics simulation of temperature and pressure effects on the intermediate length scale dynamics and zero shear rate viscosity of cis-1,4-polybutadiene: Rouse mode analysis and dynamic structure factor spectra

“…The present work complements these studies by extending the MD simulations for a model C 128 cis-1,4-PB system to somewhat lower temperatures (down to 165 K) and by analyzing also: (a) the time autocorrelation function of each Rouse mode [32] X p along the simulated C 128 cis-1,4-PB chain, and (b) the coherent [33][34][35] and incoherent [36,37] dynamic structure factors for different values of the magnitude q of the wavevector. Our results for the incoherent dynamic structure factor are then directly compared with available data obtained from NS measurements for the dependence of the incoherent relaxation times on q.…”

Quantifying chain reptation in entangled polymer melts: Topological and dynamical mapping of atomistic simulation results onto the tube model

“…We have applied our methodology to atomistic MD simulation trajectories accumulated in the recent past 24,25 for a number of model linear PE and PB melts: C 320 , C 400 , and C 500 PE melts ͑denoted as PE320, PE400, and PE500, respectively͒, C 320 , C 400 , and C 800 cis-1,4-PB ͑denoted as PBcis320, PB-cis400 and PB-cis800, respectively͒ and C 320 and C 400 trans-1,4-PB melts ͑denoted as PB-trans320, and PBtrans400, respectively͒. All PE and trans-1,4-PB systems and the PB-cis800 system are strictly monodisperse ͑polydis-persity index I =1͒, whereas the PB-cis320 and PB-cis400 systems are slightly polydisperse ͑I = 1.08 and I = 1.05 for PB-cis320 and PB-cis400, respectively͒.…”

Dynamics of Polystyrene Melts through Hierarchical Multiscale Simulations

“…[4][5][6][7][8] On the microscopic level, atomistic molecular dynamics simulations have been used for the prediction of chain diffusion of polymers with simple chemical structure, like polyethylene or polybutadiene, and with low molecular weight. [8][9][10] However, because of the broad range of length and time scales characterizing macromolecules, application of these techniques to systems with high molecular weight or to polymers with more complicated structure is not possible in most cases. 5,6,[8][9][10][11] For this reason and in order to increase the length and time scales accessible by simulations coarse-grained (CG) models have proven to be very efficient.…”

“…42 In addition, atomistic MD simulations of polyethylene 8,9 and polybutadiene 10 show an exponent of about 2.3 for slightly entangled melts.…”