Metallocene-catalyzed copolymerization

Block copolymers can be produced from terminally borane-containing polyolefins. These borane-containing POs can be synthesized by the metallocene-catalyzed (co)polymerization of olefin(s) monomer with 9-BBN as a chain transfer agent or by the metallocene catalyzed copolymerization of olefins with allyl-9-BBN [55,56], as referred to above. Alternatively, borane-containing POs were prepared by hydroboration of terminally unsaturated PO, for instance, terminally vinyl PE and terminally vinylidene PP [33-35,57]. Such method could produce diblock copolymers, such as polyethylene-block-poly(methyl methacrylate) (PE-fo-PMMA), polypropylene-foZock-poly(methyl methacrylate) (PP-fc-PMMA), polypropylene-foZock-poly(butyl methacrylate) (PP-fc-PBMA), and PP-fc-PS. 

Soares, J.B.P. and Hamielec, A.E. (1995) General dynamic mathematical modelling of heterogeneous Ziegler-Natta and metallocene catalyzed copolymerization with multiple active sites and mass and heat transfer. Polymer React. Engng, 3, 261-324. 

Yet another methodology involves the metallocene-catalyzed copolymerization of olefins with borane containing monomers (466,467). The incorporated borane group can be quantitatively converted to a hydroxy group or transformed into a stable poljnneric radical suitable for free radical grafting of acrylates. 

Development of a reduced-order model for metallocene-catalyzed ethylene-norbornene copolymerization reaction... 

PE graft copolymers were synthesized from PE-OH by Inoue et al. using ATRP techniques, adopting similar techniques as mentioned above [74]. PE-g-PMMA and Polyclhylcnc-gra/f-poly( -bulyl acrylate) (PE-g-PnBA) were prepared through the combination of metallocene-catalyzed ethylene/10-undecen-l-ol copolymerization and conversion of the copolymer into P E-g-Br, as a macroinitiator, for ATRP. Well-defined graft copolymers, PE-g-PMMA and PE-g-PnBA, were confirmed by analyses of the detached side chains. Resulting PE-g-PMMA worked well as a compatibilizer. 

Allyl PS macromonomers, which were synthesized by the ATRP of styrene with CuBr/bipyridine, have been used as comonomers in metallocene-catalyzed propylene copolymerizataions using Me2Si(2-Me-4,5-BzInd)2ZrCl2/ MAO [110]. It has been found that the incorporation of the PS macromonomers increases with a decrease in molar mass of the macromonomer and propylene concentration and increasing polymerization temperature. The highest comonomer incorporation (10.8 wt%) was achieved in the copolymerization at 70 °C. 

Luo, Y.J., Baldamus, J., and Hou, Z.M. (2004) Scanditrm Ualf-metallocene-catalyzed syndiospecific styrene polymerization and styrene-etUylene copolymerization unprecedented incorporation of syndiotactic styrene-styrene sequences in styrene-etUylene copolymers. Journal of the American Chemical Society, 126, 13910. 

Metallocene-catalyzed Z-N polymerization is finding increased use on an industrial scale. One application is the production of linear low-density polyethylene (mLLDPE),99 which is a linear polymer with short branches incorporated deliberately at various points along the chain. Short branches are produced by Z-N copolymerization of ethene with 1-butene, 1-pentene, and 1-hexene rather than through radical mechanisms of chain transfer and backbiting. Thus, the process is... 

METALLOCENE-CATALYZED ETHYLENE COPOLYMERIZATION WITH 1-OLEFINS... 

Figures 6 and 7 compare the sequence distributions and TREF chromatograms respectively for Ziegler-Natta- and metallocene-catalyzed ethylene-l-hexene copolymerizations. The lack of hlockiness in the metallocene resin in Figure 6 is demonstrated by the low levels of homopolymer triads, whereas intermolecular compositional homogeneity is shown by the narrow peak for the metallocene resin in Figure 7. It should be noted that while the narrow intermolecular distribution of comonomer content is a direct consequence of the single-site nature of the catalyst, the absence of hlockiness is a reflection of the relative magnitudes of the rate constants for insertion for the two monomers and does not speak to catalyst site diversity. The kinetics of insertion will be treated in the following section.

Schneider, M. J. Suhm, J. Muelhaupt, R. Prosenc, M.-H. Brintzinger, H.-H. Influence of indenyl ligand snbstitution pattern on metallocene-catalyzed ethene copolymerization with 1-octene. Macromolecules 1997, 30, 3164—3168. 

The ability to incorporate long-chain branches appears reasonably common among metallocene catalysts. Experimental results for LCB formation with both CGC and conventional metallocene-catalyzed polymerizations are in line with an in situ copolymerization mechanism. For copolymerization of vinyl-terminated polyethylene molecules to occur, the first requirement is the presence of termination mechanisms producing vinyl-terminated macromonomers. Secondly, the catalyst must able to incorporate these macromonomers into a growing chain. Macromers probably do not move from one active site to another, but instead insertion of macromer to another chain takes place at same site where it was formed in a intramolecular incorporation manner. 

Luo, Y., Baldamus, I, Hon, Z. Scandium half-metallocene-catalyzed syndiospecrfic styrene polymerization and styrene-ethylene copolymerization Unprecedented incorporation of syndiotactic styrene-styrene sequences in styrene-ethylene copolymers. J. Am. Chem. Soc., 126,13910-13911 (2004). 

Regarding metallocene-based catalysts, several reports concerning the copolymerization of functionalized olefins with simple a-olefins have been published. In course of their extensive studies on the metallocene-catalyzed polymerization of aluminum-protected oxygen-containing monomers, Lofgren a al. also examined ester-functionalized olefins. " ° ° Decomposition reactions could be observed in the reaction of ester functionalities and MAO. ° For example, during the reaction of tert-butyl undecenoate with MAO, slow formation of alkene fragments can be observed by NMR spectroscopic... 

Karol, F. J. UNIPOL gas phase copolymerization with SSC metallocene technology, in Metallocene Catalyzed Polymers, Benedfirt, G. M. and GoodaU, B. L., Eds., Plastics Design Lib. Norwich, NY 1998. pp. 35-42... 

Michalak A, Ziegler T, Theoretical Studies on the Polymerization and Copolymerization Processes Catalyzed by the Late-Transition Metal Complexes, in Beyond Metallocenes Next-Generation Polymerization Catalysts ACS Symp Series 857, edited by AO Patil, GG Hladky (American Chemical Society, Washington 2003), pp 154-172... 

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