We then tested our parameter set by modeling PET crystal films in different environments. We demonstrated how the most exposed layers of a PET crystal electronically respond to water, yielding an average total dipole moment of ∼1 D per residue in the interfacial layers. In contrast, the inner layers contribute very little to any electronic modulation of the most exposed layers. Moreover, we calculated the electrostatic potential surface of the crystal PET film, allowing us to map and quantify how solvent molecules modulate the elecrostatic properties of the PET film surface.