Molecular dynamics simulation of adsorbed chain's conformations of copoly (vinylidene fluoride-chlorotrifluoroethylene) at 1, 3, 5-triamino-2, 4, 6-trinitrobenzene surface

The surface absorption energy and the absorbed chains' conformation were investigated by molecular dynamics (MD) simulations using compass force field and NVT ensemble model, in the case of poly (vinylidene fluoride) (PVDF), polychlorotrifluoroethylene (PCTFE) and their copolymers being absorbed on the crystal surface of 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB). The results show that the absorption exothermic effect appeared as the distance between polymer chains and the TATB crystal surface shorten to less than 0.8 nm. The absorption effect of PVDF was strong on the TATB crystal surface and it was reverse of PCTFE. MD simulations of alternative copolymers and random copolymers, with VDF and CTFE monomer ratio varying with 1:1, 1:2, 1:3 and 1:4 respectively, were carried out. The results indicate that the composition and serial structure of polymer chain influenced significantly the chain's spatial conformations and its absorption behavior on TATB crystal surface. Especially, the alternative copolymer with the monomer ratio of 1:2 showed the best absorption effect, attaching TATB crystal surface with train -conformations. As CTFE fraction increased, the stiffness of the copolymer was also increased, while the absorption ability and absorption energy decreased gradually with more tail and loop conformations formed.