Aging of PAN solutions in DMF was accelerated above 60 °C. The thermal-induced conformational change to helix structure took place above 60 °C. Conformational change above 60 °C was accompanied by reorientation of nitrile groups. Anti-parallel oriented nitrile groups produced dipole-dipole pairs above 60 °C. Below 60 °C, the thermal-induced conformational change to planar structure took place.