weight-average molecular weights (Mn, Mw) up to 28 500 and 78 600, respectively, and a large glass transition temperature of 260℃. Using in situ poling and temperature ramping technique, the optimal temperatures (Topt) for corona poling were obtained to get the largest second-order NLO response. The electro-optical coefficient (γ33) of a polyimide at the wavelength of 830nm was up to 22 pm/V after corona poling under its Topt, and the value remained well at elevated temperatures (retained>87% at 240℃ for more than 120h). The thermal stability of NLO polyimides was studied by the UV spectrometry after poling of the films.

Some thermally stable second-order nonlinear optical (NLO) polyimides were synthesized. The polyimides were prepared by the ring-opening polyaddition of 4,4-(hexafluoroisopropylidene) diphthalic anhydride and pyromellitic dianhydride with two aromatic azodiamine derivatives as the NLO chromophores. These chromophores, based on a nitro group connected with azobenzene as the acceptor end of a donor-π-bridge-acceptor chromophore and a diamine group as the donor end, had specific chemical stability. On the basis of ZERNER'S INDO methods, according to the sum-over-states formula, a program for the calculation of nonlinear second-order optical susceptibilities was devised. The resulting polyimides had high number-average and weight-average molecular weights of up to 26,000 and 53,500, respectively, and a large glass-transition temperature of 248℃. With an in situ poling and temperature ramping technique, the optimal temperatures (Topt's) for corona poling were obtained for the largest second-order NLO response. The electrooptic coefficient (γ33) of a polyimide at a wavelength of 830 nmwas up to 21pm/V after corona poling under its Topt, and the value remained at elevated temperatures (>90.6% was retained at 240℃ for 120h). The thermal stability of the NLO polyimides was studied with UV spectrometry after poling of the films.

Polyimide (PI)/silica (SiO2) nanohybrid composite waveguide films prepared from Pyromellitic dianhydride (PMDA), 2,2-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6FHP), nonlinear optical (NLO) molecule, coupling agent APTES and hydrolysate of TEOS via sol-gel process and thermal imidization. The silicacontent in the hybrid waveguide films varied from 0 to 22.5/wt%. The PI hybrids prepared were characterized by IR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. They exhibit fair good optical transparency. The SiO2 phase is well dispersed in the polymer matrix. DSC and TGA results show that these hybrid waveguide materials have excellent thermal stability.

Coordination Chemistry Institute, Nanjing University, Nanjing 210093, People's Republic of China A newA new macrocyclic heterodinuclear FeⅢCoⅢ complex, prepared by the condensation of 2, 6-diformylpyridine N-oxide with 1, 3-diaminopropane in the presence of FeCl2. 4H2O and COCl2. 6H2O, and formulated as FeCoLCl6. C2H5OH. 8H2O, was characterized by elemental analyses, IR and Mössbauer spectra and investigated electrochemically on an ultramicrodisk platinum electrode. The results show that the electrode reaction can be thought as a nearly reversible transfer process. The diffusion coefficient is 1.93x10-6 m2 s-1 and Eo' is-0.229V (versus s. c. e) and α=0.877. The average electron transfer rate constant ko' is 3.21×10-3cms-1.

neration studies were also carried out to select right regenerant and the reuse property of this adsorbent was determined. Experimental results showed that this adsorbent exhibited maximum adsorption capacity of 98.8% at pH of 5-7, contact time for 40min, and dose of 0.2g when used to treat 50ml of Fˉ-containing aqueous solution.