Numerical estimation of unperturbed dimensions of regioirregular poly(3-ethylthiophene)s

The unperturbed chain dimensions of poly(3‐ethylthiophene)s have been calculated using the full‐relaxation optimization of conformational energies and the chain statistical mechanics with a rotational isomeric state model of two states. The computation indicates that the conjugated polymer with side groups is more flexible than without, and that the orientation of the ethyl group and the regioirregular sequences perturb the chain conformation to a certain extent. Specially, the calculated chain conformations under θ‐conditions are more rigid than those observed in good solvent. This supports experiments showing that the chain dimensions of conjugated polymers are very sensitive to variations of intermolecular interactions.