Abstract: In order to study the conduction mechanism of ladder polyphenothiazine(PTL), the electronic energy bands of the eigenstate PTLand doped PTLhave been calculated. In the calculation the polymers are treated as quasi-one-dimensional systems. Th?method of EHMO/CO is used. The results of the energy bands near the fermi level and the net charge density of each models are given. It is sug-estted that for the eigenstate PTLneutral solitons are probably the dominant charge carriers, for pron-tonic acid dopant charge solitons or polarons are the most likely contributors to the conductivity., for p-type doping polarons are the dominant charge carriers. It can be prejudged that the higher conductivity of PTLcan be reached by the means of doubte doping.

Key words: Ladder polymer, Polyphenothiazine, Conduction mechanism, EHMO/CO, Energy bands