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Temperature and Pressure Effects on Local Structure and Chain Packing in cis ‐1,4‐Polybutadiene from Detailed Molecular Dynamics Simulations
Author(s) -
Tsolou Georgia,
Harmandaris Vagelis A.,
Mavrantzas Vlasis G.
Publication year - 2006
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/mats.200500088
Subject(s) - molecular dynamics , polybutadiene , intermolecular force , chemistry , intramolecular force , thermodynamics , chain (unit) , radial distribution function , structure factor , monotonic function , pair distribution function , polymer , crystallography , computational chemistry , physics , molecule , stereochemistry , mathematics , organic chemistry , copolymer , quantum mechanics , astronomy , mathematical analysis
Summary: We present results for the temperature and pressure dependence of local structure and chain packing in cis ‐1,4‐polybutadiene ( cis ‐1,4‐PB) from detailed molecular dynamics (MD) simulations with a united‐atom model. The simulations have been executed in the NPT statistical ensemble with a parallel, multiple time step MD algorithm, which allowed us to access simulation times up to 1 µs. Because of this, a 32 chain C 128 cis ‐1,4‐PB system was successfully simulated over a wide range of temperature (from 430 to 195 K) and pressure (from 1 atm to 3 kbar) conditions. Simulation predictions are reported for the temperature and pressure dependence of the: (a) density; (b) chain characteristic ratio, C n ; (c) intermolecular pair distribution function, g ( r ), static structure factor, S ( q ), and first peak position, Q max , in the S ( q ) pattern; (d) free volume around each monomer unit along a chain for the simulated polymer system. These were thoroughly compared against available experimental data. One of the most important findings of this work is that the component of the S ( q ) vs. q plot representing intramolecular contributions in a fully deuterated cis ‐1,4‐PB sample exhibits a monotonic decrease with q which remains completely unaffected by the pressure. In contrast, the intermolecular contribution exhibits a distinct peak (at around 1.4 Å −1 ) whose position shifts towards higher q values as the pressure is raised, accompanied by a decrease in its intensity.3D view of the simulation box containing 32 chains of C 128 cis ‐1,4‐polybutadiene at density ρ = 0.849 g · cm −3 and the conformation of a single C 128 cis ‐1,4‐PB chain fully unwrapped in space.