Molecular dynamics of a 1,4-polybutadiene melt. Comparison of experiment and simulation

http://dx.doi.org/10.1021/ma991130z
Update Item Information
Publication Type abstract
School or College College of Engineering
Department Materials Science & Engineering
Program C-SAFE, Center for the Simulation of Accidental Fires and Explosions
Creator Smith, Grant D.
Other Author Paul, W.; Monkenbusch, M.; Willner, L.; Richter, D.; Qiu, X. H.; Ediger, M. D.
Title Molecular dynamics of a 1,4-polybutadiene melt. Comparison of experiment and simulation
Date 1999
Description We have made detailed comparison of the local and chain dynamics of a melt of 1,4-polybutadiene (PBD) as determined from experiment and molecular dynamics simulation at 353 K. The PBD was found to have a random microstructure consisting of 40% cis, 50% trans, and 10% 1,2-vinyl units with a number-average degree of polymerization Xn = 25.4. Local (conformational) dynamics were studied via measurements of the 13C NMR spin?lattice relaxation time T1 and the nuclear Overhauser enhancement (NOE) at a proton resonance of 300 MHz for 12 distinguishable nuclei. Chain dynamics were studied on time scales up to 22 ns via neutron spin?echo (NSE) spectroscopy with momentum transfers ranging from q = 0.05 to 0.30 Å-1. Molecular dynamics simulations of a 100 carbon (Xn = 25) PBD random copolymer of 50% trans and 50% cis units employing a quantum chemistry-based united atom potential function were performed at 353 K. The T1 and NOE values obtained from simulation, as well as the center of mass diffusion coefficient and dynamic structure factor, were found to be in qualitative agreement with experiment. However, comparison of T1 and NOE values for the various distinguishable resonances revealed that the local dynamics of the simulated chains were systematically too fast, whereas comparison with the center of mass diffusion coefficient revealed a similar trend in the chain dynamics. To improve agreement with experiment, (1) the chain length was increased to match the experimental Mz, (2) vinyl units groups were included in the chain microstructure, and (3) rotational energy barriers were increased by 0.4 kcal/mol in order to reduce the rate of conformational transitions. With these changes, dynamic properties from simulation were found to differ 20?30% or less from experiment, comparable to the agreement seen in previous simulations of polyethylene using a quantum chemistry-based united atom potential.
Type Text
Publisher American Chemical Society
Subject Polybutadiene melt; Molecular dynamics
Subject LCSH Polybutadiene
Language eng
Bibliographic Citation Smith, G. D., Paul, W., Monkenbusch, M., Willner, L., Richter, D., Qui, X. H., & Ediger, M. D. (1999). Molecular dynamics of a 1,4-polybutadiene melt. Comparison of experiment and simulation. Macromolecules, 32(26), 8857-65.
Rights Management (c)American Chemical Society http://dx.doi.org/10.1021/ma991130z
Format Medium application/pdf
Identifier ir-main,7098
ARK ark:/87278/s68g94fq
Setname ir_uspace
ID 707974
Reference URL https://collections.lib.utah.edu/ark:/87278/s68g94fq