6533b86dfe1ef96bd12ca7a2

RESEARCH PRODUCT

Molecular Dynamics of a 1,4-Polybutadiene Melt. Comparison of Experiment and Simulation

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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 A-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 an...