Fe complexes with bis(imino)pyridine ligands catalyze cyclopolymerization of 1,6-heptadiene in the presence of MMAO (modified methylalumoxiane) co-catalyst to produce the polymer containing five-membered rings in every repeating unit. The complexes with Me, Et, and Cl substituents at the N-aryl groups of the ligand produce the polymer in high yields and in high trans-cis ratio of the five-membered rings. The molecular weights of the polymers, M(n) by GPC, are higher than 6000. The polymerization promoted by the Fe complexes with bulky N-aryl groups of the ligand gives the product in lower yields, and the obtained polymer shows low trans-cis selectivity. Co complex with the ligand having 2,6-diisopropylphenyl groups at the coordinating nitrogen also promotes the cyclopolymerization to afford the polymer with cis-five-membered rings selectively. The polymerization is slower than the Fe-complex-catalyzed reaction, and the rate appears to be independent from the monomer concentration. Cyclopolymerization of the 1,6-heptadienes with phenyl or siloxy substituent at the 4-position is also catalyzed by the Fe and Co complexes in the presence of MMAO. The cyclization during the polymer growth occurs in similar trans-cis selectivity to that of unsubstituted 1,6-heptadiene. The Co complex, with addition of MMAO, catalyzes copolymerization of 1,6-heptadiene and ethylene to yield the copolymer having the trans-five-membered rings in the polyethylene chain, whereas the attempted copolymerization using the Fe catalyst gives a mixture of the homopolymers of the two monomers. The copolymerization by the Co catalyst involves chain transfer via beta-hydrogen elimination of the polymer after insertion of ethylene.
Articles you may be interested inMultilayer mirror with enhanced spectral selectivity for the next generation extreme ultraviolet lithography A point diffraction interferometer ͑PDI͒ for extreme ultraviolet lithography ͑EUVL͒ aspheric mirror measurement has been developed. In order to realize an accuracy of 0.1 nm rms, various optical error factors have been numerically analyzed and the maximum tolerable error has been determined. From the error estimation results, the optimal pinhole diameter has been determined as 0.5 m. In a PDI, air turbulence reduces the precision and accuracy because of the long optical path. In order to avoid this problem, the apparatus is filled with helium gas, which has a smaller refractive index than that of air. By using this apparatus, precision of 0.03-0.04 nm rms and a system error of 0.10 ͑0.16͒ nm rms have been obtained for a spheric mirror with numerical aperture ͑NA͒ 0.08 ͑0.15͒. In aspheric mirror measurement, an accuracy of 0.74 ͑1.18͒ nm rms for NA 0.08 ͑0.15͒ has been obtained. The accuracy becomes 0.34 ͑0.97͒ nm rms for NA 0.08 ͑0.15͒ with 36-term Zernike polynomial fitting.
We evaluated the accuracy of the point diffraction interferometer, which has been completed at the Atsugi Research Center’s Association of Super-Advanced Electronics Technologies for the precise measurement of extreme ultraviolet lithography optics. To evaluate the absolute accuracy, more precision is required. A pinhole with 0.5 μm diameter was used to generate a near completely spherical reference wave front, and helium gas filled the inside of the chamber to suppress air turbulence. With this apparatus, precision of 0.04 nm root-mean-square (rms) was achieved. Absolute accuracy was evaluated from the measurement of mirror rotation and displacement and an absolute accuracy of 0.17 nm rms was obtained for a spherical mirror with numerical aperture of 0.145. Absolute accuracy was improved to 0.11 nm rms by limiting the numerical aperture to 0.08.
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