Atomistic Simulation of Amorphous Poly(Lactic Acid) Blends: Stereodependent Miscibility and Properties

A series of amorphous bidisperse poly(lactic acid) systems containing two types of linear chains in different ratios, with different chain lengths and enantiomeric compositions, have been simulated by the molecular dynamics method, and their structural, thermophysical, and mechanical properties have been studied and compared with those of amorphous poly(L-lactic acid). The calculated average segregation parameter, the pair correlation function, and the accessible surface area of the components reveal that the effective local intermixing of the chains worsens only with the addition of the alternating poly(LD-lactic acid) chains with the same degree of polymerization. In all other cases, it becomes better. The blend characteristics change monotonically as the fraction of the shorter chains increases and can demonstrate more complex behavior in blends of chains with the same length. The effect of stereodependent miscibility, i.e., the change in local miscibility of polymer chains due to their different stereoisomeric states, has been discovered and described. The results obtained may be useful for the production of poly(L-lactic acid) with the desired properties.