Molecular design of rigid-chain polyheteroarylenes and the effect of substituents at the central heterocyclic fragment on the polyheteroarylene equilibrium rigidity

Quantum-chemical calculations and calculations by the Monte Carlo method were used for conformational analysis of heterocyclic polymers. The steric effect of various substituents on the equilibrium geometry and conformational dynamics of 1,4,5,8-naphthalenetetracarboxydiimide was studied using the AM1 semiempirical quantum-chemical method. It was shown that addition of bulky groups to the naphthalene moiety of 1,4,5,8-naphthalenetetracarboxydiimide increases conformational rigidity of the imide rings. Using the example of rigid-chain polymers containing the naphthoileneimide ring, it was demonstrated that the introduction of four bulky substituents into the structure of 1,4,5,8-naphthalenetetracarboxydiimide results in a considerable increase in the equilibrium rigidity of the polymer.