Novel thiophene-containing compound and thiophene-containing compound polymer, organic electroluminescent device, production method thereof, and image display medium

A thiophene-containing compound polymer represented by the following formula (X-II-1) or (X-II-2):

• in formulae (X-II-1) and (X-II-2), Y representing a bivalent hydrocarbon group;
• R5 representing a hydrogen atom;
• Z representing a bivalent hydrocarbon group;
• m representing 1;
• p representing an integer of 5 to 5,000;
• B and B′ each representing OCH2CH2OH, and A representing a group represented by the following formula (X-III):
• in formula (X-III), Ar1 representing a substituted or unsubstituted monovalent aromatic group;
• R1 to R3 each independently representing a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group;
• and n representing an integer of 1 to 5.