RANDOM FLUORINATED COPOLYMERS OF TETRAFLUOROETHYLENE - A STUDY OF THEINCLUSION EXCLUSION OF DEFECTS FROM THE CRYSTAL BY CONFORMATIONAL ANDPACKING ENERGY CALCULATIONS/

A conformational analysis has been performed on the isolated chains of copolymers of tetrafluoroethylene with hexafluoropropene, chlorotrifl uoroethylene or perfluoromethyl vinyl ether, in comparison with polyte trafluoroethylene. The lowest energy conformations in accordance with the chain repeating distance of polytetrafluoroethylene in the low tem perature crystal phase have been used in packing energy calculations. The results of both conformational and packing energy calculations sug gest that the -Cl group is easily tolerated in the crystal phase. The -CF3 group could also be tolerated in the crystal phase but at the cos t of conformational and crystal lattice deformations. On the contrary, it can be concluded that the -OCF3 group is excluded from the crystal phase because its presence should require high energy values and wide deformations in the unit cell parameters.