Soluble conjugated polymers

A conjugated polymer comprising:

• a polymer backbone consisting essentially of a repeat unit of the formula (I)
• wherein
• R1, R2, R′1, R′2, R3 and R4 are each independently a) selected from the group consisting of:
• alkyl, alkenyl, alkoxy, alkynyl, aryl, alkylaryl, arylalkyl, and polyalkylene oxide, each optionally substituted, which may contain one or more heteroatoms;
• or b) not present;
• A, A1, B, B1, C and D are each independently H, —SiR′R″R′″, or a polar substituent selected from the group consisting of —N+R′R″R′″, a guanidinium group, histidine, a polyamine, a pyridinium group, and a sulfonium group;
• E and F are each independently selected from the group consisting of:
• not present, —O—, —S—, —C(O)—, —C(O)O—, —N(R′)—, and —Si(R′)(R″)—;
• X is selected from the group consisting of —O—, —S—, —Se—, —N(R′)— and —C(R′)(R″)—;
• and
• Y and Z are each —N═;
• wherein R′, R″ and R′″ are each independently selected from the group consisting of hydrogen, C1-12alkyl, C1-12 alkoxy, and C3-10 cycloalkyl;
• the repeat unit comprises at least one of the polar substituent;
• and
• the repeat unit is at a density sufficient to render said polymer soluble in a polar medium having a polarity of at least that of ethyl acetate.