Lattice simulations of thermochromic distortions in poly(alkylthiophene)s

The thermochromism of poly(3-alkylthiophene)s is explained as a buckling of the main chain by torsions around the inter-ring bonds resulting in a dila tion of the pi band energy gap. Atomistic simulation calculations show that the necessity to preserve translational periodicity imposes restrictions o n the permitted torsions. Ln our model the effect of heating causes a relat ive shift of adjacent polymer chains, changing the ring stacking from 'stag gered' to 'eclipsed', in which the chains undergo a spontaneous torsion of 20 degrees.