Role of polarons in the antiferromagnetic behaviour of poly (3-dodecylthiophene)

A mathematical model was suggested and tested to elucidate the antiferromagnetic behaviour of temperature dependence of the magnetic susceptibility of poly (3-dodecylthiophene) (PDDT) which takes advantage of the physical properties of polarons and bipolarons. It has been found that the responsibility for the antiferromagnetic behaviour of temperature dependence of the magnetic susceptibility of PDDT is the conversion of polarons to bipolarons, rather than the presence of several crystalline sublattices of the polymer with different orientations of magnetic moments. The antiferromagnetic character is caused by paramagnetic polarons, the number of which decreases with lowering temperature. The proposed model was verified, with good results also for other conductive polymers exhibiting antiferromagnetic properties known from the literature.