A thienylene-arylene polymer comprised of a repeating segment containing at least one 2,5-thienylene unit selected from (I) and (II), and from about one to about three arylene units selected from (IIIa), (IIIb), and/or (IIIc) ##STR00001## wherein R is an alkyl or an alkoxy; R' is halogen, alkyl, or alkoxy, and a and b represent the number of Rs.