(US4874481-A)      N,N'-diphenylbenzidine polymer is new. Prepn. of this polymer comprises anodic polymerisation of N,N'-diphenylbenzidine of formula PhNH-B-B-NHPh, where B is 1,4-phenylene, in the presence of a supporting electrolyte and an organic base, in a polar solvent. A cyclic sweep voltammogram between -0.5 and +1.4 V (scan rate 50 mV/s) exhibits successive peaks while the polymer film undergoes colour changes from dark blue to green, then yellow and back to green and blue again, accompanied by anionic doping and then removal of dopant.    USE -   The polymers are utilised in electrochromic display devices and as electrodes in secondary battery systems.    (JP95005716-B2)      N,N'-diphenylbenzidine polymer is produced by electrolytically polymerising N,N'-diphenylbenzidine of formula (I). Pref. solvents for electrolytic polymerisation have high specific dielectric constants and dissolve electrolytes, e.g. acetonitrile, propylene carbonate, alcohol. Electrolytes are e.g. organic solvent-soluble and ion-dissociating organic or inorganic salts, complex salts, etc. e.g. (C2H5)4NBF4, LiClO4. The electrolytes are purified and vacuum-dried before use. The concns. of electrolytes are 0.01-1.0 mole, (0.05-0.3 mole). The concn. of the monomer is 1 mmole/ to 1 mole.    In an example 0.68 g of tetra-n-butylammonium perchlorate, 0.11 g of 2,6- lutidine and 0.03 g of N,N'-diphenylbenzidine were dissolved in 20ml of acetonitrile at room temp. and transferred to an electrolytic cell. ITO glass surface of resistance: 20-30 ohm) was used as working electrode, Pt wire was used as counter electrode and SCE was used as control electrode. One cycle of triangular wave (0V to 2V to 0V) was applied to the SCE at an application velocity of 50 mV/s. Homogeneous yellow film was formed on the surface of the working electrode. The film adsorbed strongly to the surface of electrode. The film was electrochemically active and turned light yellow to green to black. It is insol. in organic solvents e.g. DMF.