TECHNOLOGY FOCUS - POLYMERS - Preparation (disclosed): The new polymer is obtained by carrying out successive polymerization of a halide of formula: X-Arp-X by reaction which forms Ar-Ar coupling, in the presence of a transition-metal catalyst e.g. copper, palladium or nickel complex.X=halo, or sulfonic-acid ester group, such as CF3SO2O-;andArp=bivalent aromatic hydrocarbon ring or aromatic heterocycle which may have a substituent having thermal-dissociation soluble group.Preferred Polymer: The polymer has an aromatic ring in the repeating unit, and the thermal-dissociation soluble group is bonded with the hydrocarbon ring condensed with the aromatic ring. The aromatic ring is an aromatic-hydrocarbon ring. The thermal-dissociation soluble group is a group which carries out thermal dissociation by reverse Diels-Alder reaction, and which carries out thermal dissociation at 100-300 degrees C. Preferably, the hydrocarbon ring is a ring containing etheno group or ethano group. The polymer includes a bicyclo-octene structure of formula (1) or a bicyclo-octane structure of formula (2) in a repeating unit. The polymer has a diamine-containing repeating unit of formula: -(-Ar11-N(-Ar13)-(-Ar14-N(-Ar15)-)m-Ar12-)-, preferably of formula (3 or 4).rings A1,B'1=optionally substituted aromatic ring, with substituents optionally forming ring directly or through bivalent coupling group, preferably benzene ring, naphthalene ring, anthracene ring, or tetracene ring;S'21,S'22,R21-R26,S'31-S'34,R31-R36=H, hydroxyl, or alkyl, aromatic-hydrocarbon cyclic group, aromatic heterocyclic group, aralkyl, alkoxy, aryloxy, acyl, alkenyl, alkynyl, acyloxy, acylamino, arylamino, or heteroarylamino (all optionally substituted), with R22-R25 preferably being H or optionally substituted alkyl;X1-X4=optionally substituted 6-50C bivalent aromatic-hydrocarbon cyclic group, optionally substituted 3-50C bivalent aromatic heterocyclic group;n1-n4=0-5, preferably 0;m=0-3;Ar11,Ar12=direct bond, optionally substituted aromatic-hydrocarbon cyclic group, or optionally substituted aromatic heterocyclic group;andAr13-Ar15=optionally substituted aromatic-hydrocarbon cyclic group, optionally substituted aromatic heterocyclic group.Ar11 and Ar12 are not direct bond simultaneously. R22-R25 are not H simultaneously. EXAMPLE - (In g) 4-(10-methyl-6-(4-(phenylamino)phenyl)-12-(propan-2-yl)tricyclo(6.2.2.02,7)dodeca-2(7),3,5,9-tetraen-3-yl)-N-phenylaniline (0.71), 4,4'-dibromobiphenyl (0.39), t-butoxy sodium (0.47), and toluene (7 ml) were heated to 50 degrees C, to obtain solution (A). Tri-t-butylphosphine (0.021) was added to toluene solution (2 ml) of tris(dibenzylideneacetone)dipalladium chloroform complex (0.013), and heated to 50 degrees C to obtain solution (B). Solution (B) was added to solution (A) and heat-refluxed for 2 hours. The reaction liquid was cooled and dripped in methanol (200 ml), and a crude polymer was crystallized. The crude polymer was dissolved in toluene, reprecipitated in acetone, and filtered. The polymer was dissolved in toluene (45 ml), and bromobenzene (0.041) and t-butoxy sodium (1.8) were added and heated to 50 degrees C to obtain solution (C). Tri-t-butylphosphine (0.003) was added to toluene solution (5 ml) of tris(dibenzylideneacetone)dipalladium chloroform complex (0.013), and heated to 50 degrees C to obtain solution (D). Solution (D) was added to solution (C) and heat-refluxed for 2 hours. Toluene (34 ml) solution of N,N-diphenylamine (0.22) was added to the reaction liquid and heat-refluxed for 8 hours. The reaction liquid was cooled and dripped in methanol, to obtain a crude polymer. The crude polymer was dissolved in toluene, washed with dilute hydrochloric acid, and reprecipitated in ammonia-containing ethanol. The polymer was filtered and purified, to obtain a polymer (0.29) having a thermal-dissociation soluble group. The polymer had a weight average molecular weight of 106696, a number average molecular weight of 47937, a dispersion degree of 2.23, and a thermal-dissociation temperature of 230 degrees C. The polymer provided organic electroluminescent elements having excellent luminous efficiency and low drive voltage.