Effects of density on the local dynamics and conformational statistics of polyethylene: A molecular dynamics study

摘要: Molecular dynamics simulations of united atom (UA) linear polyethylene were performed as a function density, for systems two well-separated chain lengths (N=20, N=100). The role the exact shape torsional angle potential is investigated by invoking commonly cited alkane potentials [Ryckaert–Bellemans (R&B), Steele]. increase in second-neighbor coupling with increasing density and decreasing conformational transition rates presented quantitatively first time. simulated local orientational also studied means geometric autocorrelation functions (ACFs). These ACFs analyzed method that emphasizes distribution relaxational processes, thereby providing specific information on relevant spectral characteristics each process. For all densities studied, peaks are observed well separated Only longer chains at highest does third intermediate peak develop. Further insight into density-induced changes to obtained through angular jumps which give rise decay ACFs.