A semiconducting polymer of Formula (I): wherein X is independently selected from S, Se, O, and NR, wherein R is independently selected from hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, heteroaryl, and —CN; Ar is independently a conjugated divalent moiety; a is an integer from 1 to about 10; and n is an integer from 2 to about 5,000. The resulting semiconducting polymer is suitable for use in organic thin film transistors.