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951.
Copolymerization of ethylene and 1,5-hexadiene (HD) by zirconocene catalysts proceeded via cyclization-addition mechanism to form 1,3-didsubstituted cyclopentane structure in the polyethylene chain. The 1,3-cyclopentane structure was found to be taken in the crystalline structure of polyethylene (isomorphism) by partially chainging the trans zigzag chain into gauche conformation, thereby, inducing a transformation of orthorhombic crystal to pseudohexagonal crystal. Copolymerization of ethylene and cyclopentene (CPE) by zirconocene catalysts yielded copolymers having 1,2-disubstituted cyclopentane structure in the polyethylene chain. The 1,2-cyclopentane structure was not taken into the crystalline structure of polyethylene. The melting point (Tm) and the crystallinity (Xc) of polyethylene decreased by copolymerization of HD or CPE, and the Tm- and Xc-decreasing effect of CPE was stronger than HD. For copolymers of propylene and HD or CPE obtained with isospecific zirconocene catalyst, the isomorphism was not ovserved. 相似文献
952.
953.
Potassium alcoholate was found to initiate the anionic polymerization of 2-(N,N-diethylaminoethyl) methacrylate (AMA) to form poly[2-(N,N-diethylaminoethyl) methacrylate] (PAMA). The molecular weight of the polymers was controlled by the monomer-initiator ratio with a narrow molecular weight distribution. Increased reactivity of the initiator by chelation of the monomer to the cation may be important for the polymerization. Using potassium (4-vinylbenzyl) alcoholate as an initiator, PAMA having a vinylbenzyl group was prepared which is a macromonomer having pH sensitive amino groups in each monomeric unit. By radical copolymerization with styrene, the PAMA macromonomer was incorporated as a graft chain. 相似文献
954.
Electronic and vibrational spectra of poly(p-phenylenevinylene) doped with donors or acceptors have been studied, together with the spectra obtained for the radical ions and divalent ions of its oligomers. The electronic absorption spectra of doped poly(p-phenylenevinylene) in the region from visible to near-infrared show two bands for the H2SO4-doped species and one very broad band for the Na-doped species. On the basis of the analyses of resonance Raman spectra, the two electronic absorption bands of the H2SO4-doped species are attributed to a polaron-lattice structure, whereas the broad band of the Na-doped species is attributed to overlapping absorptions associated with localized electronic levels of polarons and bipolarons. A Pauli spin susceptibility of the H2SO4-doped species is explained by the polaron-lattice structure. 相似文献
955.
956.