Low band gap semiconducting polymers

A polymer of formula (II):

• wherein:
• n is 2-100;
• A is a bond;
• and R1 is H, (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkoxycarbonyl, cyano, halo, nitro, ReOSO2—, carboxy, trifluoromethyl, aryl, aryl(C1-C12)alkyl, —CH2CH2O(CH2CH2O)mCH3, or NRaRb;
• or A is O, S, or Se and R1 is H, (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C3-C12)cycloalkyl, (C1-C12)alkanoyl, trifluoromethyl, aryl, or aryl(C1-C12)alkyl, or —CH2CH2O(CH2CH2O)mCH3;
• wherein each aryl is optionally substituted with one or more (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, (C1-C12)alkoxycarbonyl, cyano, halo, nitro, carboxy, trifluoromethyl, trifluoromethoxy, or methylenedioxy;
• B is a bond;
• and R2 is H, (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, cyano, halo, nitro, ReOSO2—, carboxy, trifluoromethyl, aryl, aryl(C1-C12)alkyl, —CH2CH2O(CH2CH2O)mCH3, or NRcRd;
• or B is O, S, or Se and R2 is H, (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, trifluoromethyl, aryl, or aryl(C1-C12)alkyl, or —CH2CH2O(CH2CH2O)mCH3;
• wherein each aryl is optionally substituted with one or more (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, (C1-C12)alkoxycarbonyl, cyano, halo, nitro, carboxy, trifluoromethyl, trifluoromethoxy, or methylenedioxy;
• Ra and Rb are each independently (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, aryl, aryl(C1-C12)alkyl, —CH2CH2O(CH2CH2O)mCH3, or (C1-C12)alkoxycarbonyl;
• or Ra and Rb together with the nitrogen to which they are attached form a morpholino, thiomorpholino or pyrrolidino ring;
• Rc and Rd are each independently (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, aryl, aryl(C1-C12)alkyl, —CH2CH2O(CH2CH2O)mCH3, or (C1-C12)alkoxycarbonyl;
• or Rc and Rd together with the nitrogen to which they are attached form a morpholino, thiomorpholino or pyrrolidino ring;
• Re is H or (C1-C12)alkyl;
• m is 0-5;
• D is absent or is phenyl, thienyl, bithienyl, terthienyl, quaterthienyl, or fluorenyl, which phenyl, thienyl, bithienyl, terthienyl, quaterthienyl, and fluorenyl is optionally substituted with one or more (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, (C1-C12)alkoxycarbonyl, cyano, halo, nitro, carboxy, trifluoromethyl, trifluoromethoxy, or methylenedioxy;
• and
• E is absent or is phenyl, thienyl, bithienyl, terthienyl, quaterthienyl, or fluorenyl, which phenyl, thienyl, bithienyl, terthienyl, quaterthienyl, and fluorenyl is optionally substituted with one or more (C1-C12)alkyl, (C2-C12)alkenyl, (C2-C12)alkynyl, (C1-C12)alkoxy, (C3-C8)cycloalkyl, (C1-C12)alkanoyl, (C1-C12)alkanoyloxy, (C1-C12)alkoxycarbonyl, cyano, halo, nitro, carboxy, trifluoromethyl, trifluoromethoxy, or methylenedioxy;
• or a salt thereof.