NOVELTY - Preparing a copolymer comprises: (a) providing at least one first thiophene monomer and at least one second thiophene monomer, which is different from the first monomer (where the first and second monomers comprise a first and second functionality at second and fifth positions, respectively, in which the second functionality is adapted to react with the first functionality); and (b) reacting the first and second monomers in the presence of a transition metal to form a copolymer.    USE - The copolymer is useful in: an ink composition; and a coated substrate or a device including organic LED or OPV device (all claimed).    DETAILED DESCRIPTION - Preparing a copolymer comprises: (a) providing at least one first thiophene monomer and at least one second thiophene monomer, which is different from the first monomer (where the first and second monomers comprise a first and second functionality at second and fifth positions, respectively, in which the second functionality is adapted to react with the first functionality and each of the monomers comprise substituents (comprising an oxygen bonded to the thiophene ring) at third and fourth positions); and (b) reacting the first and second monomers in the presence of a transition metal to form a copolymer. INDEPENDENT CLAIMS are included for:    (1) a copolymer comprising at least one first thiophene repeat unit and at least one second thiophene repeat unit, where the first unit is different from the second unit, each of the first and second unit comprises substituents (comprising an oxygen bonded to thiophene ring) at the third and fourth positions and each of the first unit and the second unit is connected at second and fifth positions to neighboring repeat units or end groups;    (2) a device comprising an active layer that comprises the above copolymer in optionally doped or undoped form;    (3) an organic LED (OLED) comprising a hole injection layer that comprises the above copolymer in optionally doped form;    (4) an organic photovoltaic device comprising a hole transport layer that comprises the above copolymer in optionally doped form; and    (5) a method comprising providing first thiophene monomer comprising the first repeat unit and first functionality at second and fifth positions, where the first functionality is (-X), the first thiophene monomer is more stable during purification by distillation and is less reactive during polymerization than the second thiophene monomer comprising the second repeat unit and second functionality at the second and fifth positions in which the second repeat unit is different from the first repeat unit and the second functionality is identical to the first functionality, providing at least one third thiophene monomer comprising a third repeat unit and a third functionality, where the third repeat unit is identical to the second unit and the third functionality comprises metal halo groups of formula (-MgX) (a1), (-MnX) (b1), (-ZnX) (c1), (-MgX:LiY1) (d1) or (-Sn(R)3) (f1), boron group of formula (-B(OR)2) (e1) or silicon group of formula (-Si(R)3) (g1), and reacting the first thiophene monomer and the third thiophene monomer in the presence of the transition metal to form the copolymer.    X, Y1 = halo; and    R = an alkyl group.