Synthesis of isotactic polypropylene-based block copolymers

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Isotactic poly (propene) (PP) having a terminal vinylidene group (number average molecular weight=5,300, melting point=114ﾟC) was prepared with the ethylenebis (4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride-methylaluminoxane catalyst system. The polymer produced was treated with borane-dimethylsulfide in toluene, followed by reacting with pentane-1,5-di (magnesium bromide) to obtain magnesium bromide (MgBr) -terminated isotactic PP.The polymer was brought into contact with iodine to give isotactic PP having an iodine group at the chain end in about a 85% yield. Polymerization of methyl methacrylate was then conducted at -78ﾟC using the MgBr-terminated PP as an initiator to synthesize isotactic PP-block-poly (methyl methacrylate) copolymer.In order to apply this method to the synthesis of A-B-A type block copolymers, an attempt was made to prepare alpha, omega-divinyl PP.We have previously reported that the Zn-polymer bonds of PP obtained with the TiCl_3-AlEt_2Cl-ZnEt_2 catalyst ca … More n be converted to vinyl groups in fairly good yield by the coupling reaction with allyl bromide. Therefore, bis (3-butenyl) zinc (BBZ) and bis (7-octenyl) zinc (BOZ) were synthesized and used as cocatalyst and/or chain transfer reagent combined with TiCl_3. These catalyst systems gave isotactic poly (propene), of which melting points were around 160ﾟC.The bis (alkenyl) zinc compounds acted as a chain transfer reagent to give zinc-terminated polymers with low molecular weight.IR,^1H NMR and ^<13>C NMR analyzes of the produced polymers indicated the incorporation of 7-octenyl group at the initiation chain end. However, 3-butenyl group was not observed, which may be probably due to back-biting cyclization. In addition, BOZ could copolymerize with propene to give PP which had Zn-carbon bonds in side chains. The zinc-carbon bond at the termination end and the side chains were converted to vinyl groups by coupling with allyl bromide to obtain alpha, omega-divinyl PP having a small amount of 8-nonenyl groups as side chain.Synthesis of block copolymers from the alpha, omega-divinyl PP by the method described above are now being carried out. Less