Alternating ethylene/cyclopentene copolymers

Natta, G DeU Asta, G Mazzanti, G Pasqunn, I. Valvassori, A. ZambeUi, A. Crystalline, alternating ethylene-cyclopentene copolymers and other ethylene-cycloolefin copolymers. Makromol. Chem. 1962, 54, 95-101. 

SCHEME 20.25 Strictly alternating ethylene/cyclopentene copolymers via ROMP (TsH = p-toluenesulfonhydrazide). 

Synthesis of Ethylene/Cyclopentene Copolymers Having Alternating and... 

Fujita, M. Coates, G. W. Synthesis and characterization of alternating and multiblock copolymers from ethylene and cyclopentene. Macromolecules 2002, 35, 9640-9647. 

Alternating copolymers of ethylene with olefins containing double bonds in the cis configuration, like ds-2-butene, cyclopentene, cycloheptene,115 and norbomene,116 have been described. Recently also copolymers of carbon monoxide with styrene and styrene derivatives, having syndiotactic117 and isotactic118 configurations, have been synthesized and characterized. 

Metallocene catalysts show low r values, which allows easy incorporation of bulky cycloolefins into the growing copolymer chain. Surprisingly, the ethylene reactivity ratio in copolymerisation with cyclopentene in the presence of a (ThindCH2)2ZrCl2-based catalyst (r = 2.2) and in copolymerisation with norbornene in the presence of catalysts characterised by Cs and Ci symmetry (ri 3.4 and 3.1 respectively) is considerably lower than that for the copolymerisation of ethylene with propylene (r = 6.6 at 37 °C). Various catalysts produce copolymers of structures that are between statistical and alternating [468]. 

Preferred olefins in the polymerisation are one or more of ethylene, propylene, 1-butene, 2-butene, 1-hexene, 1-octene, 1-pentene, 1-tetradecene, norbornene and cyclopentene, with ethylene, propylene and cyclopentene. Other monomers that may be used with these catalysts (when it is a Pd(II) complex) to form copolymers with olefins and selected cycloolefins are carbon monoxide (CO) and vinyl ketones of the general formula H2C=CHC(0)R. Carbon monoxide forms alternating copolymers with the various olefins and cycloolefins. 

The co-polymerization of ethylene and 2-butene with the McConville catalyst 87 has been reported. NMR analysis of the co-polymer indicated that only the tram-isomer of 2-butene was incorporated.1 6 Ethylene and cylopentene have been co-polymerized with the MAO-activated complex 138 working at very low ethylene pressure.605 The almost regularly alternating poly( ethylene- //-m-l,2-cyclopentene) co-polymer exhibited a T of 10 °C. This copolymer is a crystalline plastomer with high structural disorder.1237 Furthermore, multi-block co-polymers were synthesized by changing the ethylene pressure during polymerization. This way, the various blocks are characterized by a different amount of cyclopentene units.605... 

Bis(phenoxyimine) titanium complexes have also been employed in the living copolymerization of ethylene/cyclic olefins and ethylene/l,5-hexadiene. Utilizing 31/MAO and varying ethylene pressure, a series of poly(E-co-CP)s with different cyclopentene contents were prepared (Fujita and Coates, 2002). When ethylene pressure was low (<1 psi), an almost perfectly alternating copolymer was formed (Mn = 21000 g/mol, Mw/Mn = 1.34, T = 10.1 C). However, the use of higher ethylene pressures (3 psi) resulted in the formation of a random copolymer containing 36 mol% cyclopentene (M = 133000g/mol,Mw/Mn = 1.24, T =—A.S°C). Tri- and multiblock copolymers were synthesized in which the constituent blocks differed in their cyclopentene content. 

---