Abstract. The potential of a number of tetraaza-macrocyclic complexes of cobalt and nickel to mediate the photoreduction of carbon dioxide has been studied. Carbon monoxide and hydrogen are the main products, which result from illumination of an aqueous solution containing Ru(2,2'-bipyridine):+ as sensitizer, ascorbic acid as sacrificial eletron donor and a tetraaza-macrocyclic complex as relay. Their ratio strongly depends upon the relay compound used. The complexes can be used as electrocatalysts for CO, reduction at a mercury electrode since they lower the overpotential for CO, reduction showing turnover numbers/hour of approximately 3. A minimum potential is required to induce reaction of electrocatalysts and CO, (and H,O). Finally, the redox properties of the macrocyclic metal complexes at p-GaP and p-GaAs photocathodes in acetonitrile are compared with those observed at Pt.

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A cross-linked nonlinear optical urethane polymer is prepared from 4-[ (2-hydroxyethyl)sulfonyl] -4'-[N,N-bis(2-hydroxyethyl)amino] azobenzene (1) and toluene diisocyanate by simultaneously corona poling and cross-linking at 145 °C for only 30 min. This material shows very promising results as NLO material: SHG measurements show a resonantly enhanced <¿33 value of 60 pm/V at 1064 nm 1 day after poling and a 34% decrease after 800 h at 70 °C. Moreover, electrooptic measurements on contact poled samples at 175 °C result in a value of the pockels constant r33 of 12.3 pm/V. Poling at 190 °C results in a decrease of less than 40 % after 100 h at 1506 C. Additional measurements show a linear interrelation between the electrooptic and the pyroelectric constant, as well as between the electrooptic constant and the dielectric polarization.

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High molecular weight liquid-crystalline polyhydroxyethers, containing functional hydroxy groups, were synthesized from an aromatic diol and the diglycidylether of an aromatic diol. The polymers showed a liquid-crystalline melt when about 70% or more of the aromatic units in the chain were biphenyl units. Tensile modulus values varied from 3 GPa for as-cast films to 6 GPa for drawn films. These polymers are potentially suitable candidates to reinforce common thermoplastics by reactive blending. For this purpose polyhydroxyethers have been prepared, having a liquidcrystalline melt in the processing range of PET, viz. 260-290ЊC.

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1 13.71" 1 .oo 1 .oo 94 2a 12.08 0.85 0.84 95 2b 10.11 0.70 0.68 95 2c 7.75 0.50 0.5 1 98Abstract. Acid hydrolysis, under relatively mild conditions (3N HCI, 100°C), of a series of homopolymers of N-vinyl-N-methylacetamide, and copolymers thereof with vinyl acetate or methyl acrylate, afforded poly(N-vinyl-N-methylamine), poly(N-vinyl-N-methylamine-co-vinyl alcohol) and poly(N-vinyl-N-methylamine-co-acrylic acid) in almost quantitative yield. A simple and practical route to poly(N-vinyl-N-methylacetamide-co-acrylic acid) and poly(N-vinyl-N-methylacetamide-co--vinyl alcohol) has been developed and some kinetic results relating to the hydrolysis step are given. The products were characterized by viscometry, elemental analysis and NMR spectroscopy.