Studies of Adjacent Re-Entry Folds of Chains of Syndiotactic 1,2-Poly(1,3-butadiene) by Molecular Mechanics Calculations

The mode of packing and the adjacent re-entry folds of chains of syndiotactic 1,2-poly(1,3-butadiene) have been studied by molecular mechanics calculations with the use of various sets of potential functions. The results of the packing analysis indicate that the crystal grows preferentially along the [100] and [110] directions. Models of fold have been built up on an infinite ab surface completely covered by adjacent re-entry folds in the (100) and (110) planes. The results of energy minimizations show that several almost isoenergetic folds, constituted by four monomeric units, can be realized in the (100) planes, while the fold in the (110) planes has higher energy. The calculated value of the work of fold is in satisfactory agreement with that derived by crystallization kinetics reported in literature.