Synthesls and Characterization of Block Copolymers consisting of Conjugated Monomers and Ethylene by Means of Active Site Modification

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The following results were obtained from the study on synthesis and characterization of block copolymers by means of active site modification. First, block copolymer consisting of styrene and ethylene bearing narrow molecular weight distribution has been synthesized by means of active site modification performed by the addition of t-diamines to living poly(styrene). Similarly, block copolymer consisting of isoprene and ethylene segments has been synthesized by means of "active site modification" performed by adding appropriate t-diamines such as N,N,N,N-tetramethylethylenediamine (TMEDA) and sparteine to the living polymer initiated with alkyllithium. Block copolymers formed have a relative narrow molecular weight distribution and retained the mainly 1,4-units in the microstructure of IP segment. Such block copolymerization with ethylene could not be admitted in the absence of the t-diamines and only homopolymer of isoprene was recovered. Block copolymer of ethylene and methyl methacrylate with alkyllithium complexed with tert-diamines by means of chain end modification by diphenyl ethylene was synthesized. These were applied to homopolymerization of ethylene and isoprene. The polymerization of ethylene initiated with alkyllithiums complexed by TMEDAN was studied by using ^<13>C NMR spectroscopy and GPC. In the cases of s-butyllithium and t-butyllithium, both initiation and termination chain end were determined by ^<13>C NMR spectra, and GPC elution curves of the polymers shifted to higher molecular weight side with reaction time. This suggests that the polymerization of ethylene initiated with alkylgroups in alkyllithiums and propagating species have a living nature. In the case of isoprene, the microstructure of the polymers could be controlled by the activesite modification.