Influence of molecular chain behavior on mechanical properties of poly-L-lactic acid by molecular dynamics method

Abstract

Generally, poly-L-lactic acid (PLLA) is being developed in various medical devices; it is still urgent to elucidate the correlation between molecular chain deformation behavior and mechanical properties such as stress. In addition, there are few cases where molecular dynamics simulation is used to compare the molecular chain deformation behavior which is difficult to evaluate in the micro region and the potential energy and evaluate mechanical properties like stress. Therefore, in this study, in order to compare molecular chain deformation behavior of PLLA using molecular dynamics method, analysis models of initial orientation 0 °, 45 °, 90 ° and four random oriented models were prepared. In addition, tensile simulation was carried out using affine deformation, and the influence on the mechanical properties exerted by molecular chain deformation behavior was evaluated. As molecular chain deformation behavior, molecular chain length, molecular chain angle, distance between centers of gravity between molecular chains were determined, and in comparison with potential energy and stress generated in tensile simulation for evaluating mechanical behavior. As a result, it was shown that the model showing the curing behavior increased the stress after reaching the lower yield point, and the model not showing a remarkable increase after the stress reached the lower yield point. In addition, it was suggested that the elongation and angle change of the molecular chain had a large influence on the stress, and among them, the influence on the stress exerted by the angle change was the largest.