PolyParGen provides OPLS-AA and Amber force field parameters for polymers or large molecules.
In the case that PolyParGen generates OPLS-AA parameters, PolyParGen leverages LigParGen  and BOSS .
On the other hand, PolyParGen leverages Antechamber  and ACPYPE  to make Amber parameters.
If users want to use the atomic charge of ab initio calculation, user just select the option of ab initio calculation. Ab initio software is NWChem .
Also, the supports input file is CML format at current version.
The previous version (v1) supports PDB, MOL, MOL2 and CML.
The support of PolyParGen version 1 has been suspended to create accurate potential parameters.
If you want to make the OPLS-AA force field parameters for organic molecules and ligands which have within 200 atoms, you should use LigParGen service.