Side chain dynamics in poly(ethyl acrylate) studied by molecular dynamics simulation

A molecular dynamics (MD) trajectory of 1.0 ns duration has been computed f or a methyl-terminated atactic poly(ethyl acrylate) using force field param eters which we determined by ab initio molecular-orbital calculations for s mall molecules (RHF/6-31G level). Local side chain motions were clarified b y analyses of the MD trajectory. The torsional angle autocorrelation functi ons (TACF) were calculated for each dihedral angle in the side chain. All o f the TACF were strongly non-exponential. The entire side chain rotation wa s an asymmetric 180 degrees jump motion with a rapid torsional oscillation within stable and metastable conformations, while ethyl group motion around the O(non-carbonyl)-CH2 bond in the side chain was characterized by rapid torsional motion in the angle range from 60 to 300 degrees involving an obs cure three-site jump motion.