TECHNOLOGY FOCUS - POLYMERS - Preferred Copolymer : The aryl group having a formula weight of 90 or more is at least one group selected from n-alkyl, I-alkyl, s-alkyl and alkoxy group.Preferred Process : A process for producing the copolymer comprises reacting two or more monomers selected from monomers represented by general formulae (1), (2) and (3) with monomers represented by general formulae (4) and/or (5).Ar1, Ar2, Ar3 = arylene, divalent heterocyclic or divalent aromatic amine group ;E1, E2 = monovalent heterocyclic group, monovalent group derived from a metal complex coordinated to a heterocyclic group, or aryl group having a formula weight of 90 or more ;Y1 - Y8 = dissociative groups.A process for producing the copolymer comprises reacting monomers represented by general formulae (1) - (5), where Y1 - Y8 are independently a halogen atom, an alkyl sulfonyloxy group or arylsulfonyloxy groups in the presence of an Ni(0) complex. Another process for producing the copolymer comprises polymerizing monomer represented by general formulae (1) - (5), in which Y1 and Y2 are independently groups represented by -B(OR11)2, Y3 and Y4 are halogen atoms, alkylsulfonyloxy or arylsulfonylxoy groups, Y5 and Y6 are groups represented by -B(OR11)2, halogen atoms, alkylsulfonyloxy or arylsulfonylxoy groups ; Y7 is a group represented by -B(OR11)2, and Y8 is a halogen atom, an alkylsulfonyloxy or an arylsulfonylxoy group, in the presence of a Pd(0) catalyst.R11 = H atom or alkyl group.Preferred Composition : The polymer composition contains two or more different invented copolymers.Preferred Element : The polymeric luminescent element has a luminescent layer between an anode and a cathode. In the polymeric luminescent element, an electric conductive layer and/or an insulation layer is provided adjacent to the electrode between at least one electrode and the luminescent layer, an electron-transporting layer is provided adjacent to the luminescent layer between the cathode and the luminescent layer, and a positive-hole transporting layer is provided adjacent to the luminescent layer between the anode and the luminescent layer. WIDER DISCLOSURE - A polymer composition comprises a polymer which has a number-average molecular weight of 10 3 - 108 in terms of polystyrene and emits fluorescence in the solid state, and the invented copolymer. A polymeric luminescent element has a luminescent layer which contains the invented copolymer or polymer composition.    EXAMPLE - Bis(1,5-cyclooctadiene)Ni(0) was added to a mixture of compound (E) (0.36 g), N,N'-bis(4-bromophenyl)-N,N'-bis(4-n-butylphenyl)1,4- phenylene diamine (0.17 g), p-bromotoluene (6.8 mg), 2,2'-bipyridyl (0.34 g) and tetrahydrofuran (20 ml), and the mixture was reacted at 60 degrees C for 3 hours in an N2 atmosphere. The resulting reaction solution was poured into a 25% ammonia water (10ml)/methanol (20ml)/ion-exchanged water (50 ml) mixture solution and the mixture was stirred for 1.5 hours. The deposits were separated by filtration. The solid was washed and purified by an alumina column so as to obtain a polymer (1). A polymer (2) was produced by reacting 1,7-dibromo-9,9-dioctylfluorene, 2,7-dibromo- 9,9-diisopentylfluorene, 2,2'-bipyridyl and tetrahydrofuran in the presence of bis(1,5- cyclooctadiene)Ni(0). A mixture of polymer (1) and (2) (wt ratio 3 : 7) was coated on a poly(ethylenedioxythiophenone)/polystyrenesulfonic acid film formed on a glass plate. A polymeric luminescent element containing this copolymer film as a luminescent layer, emitted at a wavelength of 468 nm and had a brightness decrease of 20 % after 130 hours.