Coordination polymerization ethylene-propylene copolymers

Various types of well-defined block copolymers containing polypropylene segments have been synthesized by Doi et al. on the basis of three methods (i) sequential coordination polymerization of propylene and ethylene 83-m>, (ii) transformation of living polypropylene ends to radical or cationic ones which initiate the polymerization of polar monomers 104, u2i, and (iii) coupling reaction between iodine-terminated monodisperse polypropylene and living polystyrene anion 84). In particular, the well-defined block copolymers consisting of polypropylene blocks and polar monomer unit blocks are expected to exhibit new characteristic properties owing to the effect of microphase separation. 

Well-defined diblock (P—R) and triblock (P R — P) copolymers consisting of the polypropylene block (P) and the ethylene-propylene random copolymer block (R) were prepared by adding ethylene monomer during the living coordination polymerization of propylene with the soluble V(acac)3/Al(C2H5)2Cl/anisole catalyst U1). 

Examination of Figure 3.27 shows that the constrained geometry complex is a coordinatively unsaturated chromium(III) alkyl that polymerizes ethylene, however, it does not react with 1-hexene to provide an ethylene/1-hexene copolymer. In reactions with propylene, a head-to-tail dimerization reaction takes place without any homopolymerization of higher 1-olefins. 

Mason, A.F., and Coates, G.W. (2007) Coordination polymerization synthesis of new homo- and copolymer architectures from ethylene and propylene using homogeneous Ziegler-Natta polymerization catalysts. Macromolecular Engineering, 1,217-249. 

The discovery of coordinate polymerization of oxirane led to an enormous expansion in the range of polyether structures that could be synthesized. Some of the remarkable synthesis chemistry is outlined in Section III. Coordinate copolymerization further increased the range of polymer structures that could be synthesized in highly controlled ways. Two examples have already been described copolymers of epichlorohydrin and ethylene oxide (71) and of propylene oxide and allyl glycidyl ether (94, 137). The activation energy for copolymerization of epichlorohydrin and maleic anhydride was found to be 14.5 kcal/mol, and the polymerization rate is dependent on temperature and proportional to catalyst concentration (138-140). 

The preparation of ethylene copolymers (or terpolymers) such as linear low-density polyethylenes (LLDPE), ethylene/propylene elastomers (EP), ethylene/ propylene/diene terpolymers (EPDM) is also based on these catalytic systems. Stereoregular polyisoprene and polybutadiene elastomers are also obtained by this method of polymerization the formation of 1,4-m-polydienes requires the prior double coordination of the monomer onto the growing active center ... 

Polyethers are prepared by the ring opening polymerization of three, four, five, seven, and higher member cyclic ethers. Polyalkylene oxides from ethylene or propylene oxide and from epichlorohydrin are the most common commercial materials. They seem to be the most reactive alkylene oxides and can be polymerized by cationic, anionic, and coordinated nucleophilic mechanisms. For example, ethylene oxide is polymerized by an alkaline catalyst to generate a living polymer in Figure 1.1. Upon addition of a second alkylene oxide monomer, it is possible to produce a block copolymer (Fig. 1.2). 

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