Semiconducting polymers

A monomer of formula Ia

• R2—U—R3 Ia
• wherein U is a unit of formula
• I
• wherein the asterisks indicate a link to neighboring groups,
• X is O, S or NRx,
• R is, on each occurrence identically or differently, H, F, Cl, Br, I, CN, or straight-chain, branched or cyclic alkyl with 1 to 35 C atoms, in which one or more non-adjacent C atoms are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CR0═CR00— or —C≡C— and in which one or more H atoms are optionally replaced by F, Cl, Br, I or CN, or denote aryl, heteroaryl, aryloxy, heteroaryloxy, arylcarbonyl, heteroarylcarbonyl, arylcarbonyloxy, heteroarylcarbonyloxy, aryloxycarbonyl or heteroaryloxycarbonyl having 4 to 30 ring atoms that is unsubstituted or substituted by one or more non-aromatic groups R1,
• Rx is on each occurrence identically or differently straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more non-adjacent C atoms are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, O—CO—O—, —CR0═CR00— or —C≡C— and in which one or more H atoms are optionally replaced by F, Cl, Br, I or CN,
• R0 and R00 are independently of each other H or optionally substituted carbyl or hydrocarbyl optionally comprising one or more hetero atoms,
• R1 is on each occurrence identically or differently H, halogen, —CN, —NC, —NCO, —NCS, —OCN, —SCN, —C(═O)NR0R00, —C(═O)X0, —C(═O)R0, —NH2, —NR0R00, —SH, —SR0, —SO3H, —SO2R0, —OH, —NO2, —CF3, —SF5, optionally substituted silyl, carbyl or hydrocarbyl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more hetero atoms, or P-Sp-,
• P is a polymerizable or crosslinkable group,
• Sp is a spacer group or a single bond,
• X0 is halogen, and
• R2 and R3 are, independently of each other, Cl, Br, I, O-tosylate, O-triflate, O-mesylate, O-nonaflate, —SiMe2F, —SiMeF2, —O—SO2Z1, —B(OZ2)2, —CZ3═C(Z3)2, —C≡CH or —Sn(Z4)3, wherein Z1-4 are alkyl or aryl, each being optionally substituted, and two groups Z2 may also form a cyclic group.