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3-Plentamene prepared from aeetylacetone in our laboratury contained 91.7％ trans- and 8.3％ cis-isomers．Homopolymerization of 1，3-pen

tadiene and its eopoly-merization with butadiene were earried out with heterogeneous catalysts prepared from NdCl3-C2H5OH-Al(C2H5)3 in hydrocarbon solvent．The results obtained showed that only trans-isomer of 1．3-pentadiene can be polymerized with these catalyst to high molecular weight polymer with high conversion．The structure of the polypen-tadiene has been examined by IR．NMR and X．ray spectra．It was found that the polymer contains predomlnantly cis-1，4-unit with isotactic configuration and exhibits erystallinity．The data obtained by IR and dynamic mechanical method indicated that the product of copolymerization by above mentioned catalyst system is a randum eopolymer．