Reverse Mapping Algorithm for Multi-scale Numerical Simulation of Polylactic Acid

An algorithm is proposed to convert the coarse-grained A-graft-B model of polylactic acid into the atomistic representation. In the A-graft-B model the atoms of the backbone are mapped onto A beads, which form the linear backbone of the coarse-grained macromolecule, the methyl groups are mapped onto B side pendants. The algorithm restores atomic positions based on positions of coarse-grained beads with the help of pre-defined chain fragments, called templates. The dimensions of the templates are adjusted by affine transformation to ensure coincidence of the backbone in coarse-grained and atomistic representation. The transition between coarse-grained and atomistic models conserves information about the fine structure of polymer chains. The restored configurations are suitable for further molecular-dynamic simulations. Both atomistic and coarse-grained representations require standard GROMACS software. The algorithm can be used for reverse mapping of other A-graft-B polymer models.