Triarylamine polymer, process for producing the same, and use thereof

A triarylamine polymer represented by formula (1):

• wherein Ar1 and Ar2, are different from each other and are, independent of each other, any one of the following formulas (4) to (8):
• wherein
• R2 and R3 are, independent of each other, a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an alkenyl group, an aryl group, an arylamino group or a heteroaryl group,
• R2 may, together with one or more substituents, form a condensed ring,
• A is S, O, SO2, CO, CH2 or(CH3)2,
• b is an integer of from 0 to 4,
• c is an integer of from 2 to 4, and
• d is an integer of from 1 to 4,
• Ar3, Ar4, Ar5, Ar6 and Ar7 are, independent of one another, an unsubstituted or substituted C6-60 aromatic group, and
• Ar3 and Ar4 are the same, and
• m is an integer of at least 1,
• wherein the triarylamine polymer has a weight average molecular weight of from 16000 to 100,000 as calculated as polystyrene.