Propylene oxide copolymerisation

The coordination polymerisation and copolymerisation of heterocyclic monomers have been restricted in industry to a much smaller volume than the polymerisation and copolymerisation of hydrocarbon monomers polyether elastomers from epichlorohydrin and ethylene oxide or propylene oxide, and allyl glycidyl ether as the vulcanisable monomeric unit, are produced on a larger scale [4-7],... 

The tendency towards alternation in the oxirane/cyclic acid anhydride system with the zinc-based coordination catalyst is connected, according to literature data [193], with the stronger nucleophilic properties of the oxygen atom of the zinc alcoholate species and the weaker electrophilic properties of the zinc atom in such species compared with the respective properties of zinc carboxylate species. Studies of the copolymerisation of propylene oxide and maleic anhydride in the presence of catalysts such as diethylzinc-monoprotic compound (1 1) showed an increasing tendency towards alternation in systems with catalysts of decreasing electrophilicity of the zinc atom [186], which may corroborate the coordination mechanism proposed scheme (24). 

Catalysts derived from reaction systems such as triethylaluminium-water and triethylaluminium-water-acetylacetone [225], triethylaluminium-triphe-nylphosphine [226], triethylaluminium-pyrogallol [209] and rare-earth metal phosphonate- triisobutylaluminium-glycerol [227] appeared to be effective in the copolymerisation of propylene oxide and carbon dioxide, yielding high molecular weight polypropylene ether-carbonate)s (Table 9.4) but not the respective alternating copolymer which is polypropylene carbonate). 

Although propylene oxide has been the oxirane most widely studied in copolymerisation with carbon dioxide, there are a variety of other oxiranes capable of coordination copolymerisation with carbon dioxide (Table 9.4). 

Copolymerisation of propylene oxide as well as other oxiranes with carbon dioxide in the presence of zinc-based coordination catalysts is generally accompanied with the formation of a cyclic five-membered carbonate, propylene carbonate or another alkylene carbonate [147,206,207,210,212,230]. The alky-lene carbonate, however, is not the precursor for poly(alkylene carbonate), since it hardly undergoes a polymerisation under the given conditions [142-146],... 

Studies of the regioselectivity of oxirane/carbon dioxide copolymerisation showed the polar effect exerted by the ring substituent, but not the bulkiness, to be the factor determining the direction of ring opening [231,232]. In the case of propylene oxide/carbon dioxide copolymerisation, C g—O bond cleavage... 

It may be mentioned that the use of ionic nucleophilic initiators, instead of zinc-based coordination catalysts, in order to promote propylene oxide/carbon dioxide copolymerisation, did not result in the formation of any copolymer but led to the cyclic carbonate, propylene carbonate [194,236,237]. Also, zinc-based coordination catalysts with non-condensed zinc atoms in their molecules (formed by the reaction of diethylzinc with a monoprotic compound such as... 

As regards oxirane/carbon dioxide copolymerisation with (dmca) A1C1, it yields low molecular weight propylene oxide/carbon dioxide copolymers with a prevailing content of ether linkages as well as cyclohexene oxide/carbon dioxide copolymers of predominantly carbonate linkages. 

The copolymerisation of propylene oxide and carbon disulphide was carried out with a catalyst consisting of diethylzinc and an electron donor, such as tertiary amine, tertiary phosphine or hexamethylphosphoric triamide, in... 

It is worth noting that catalysts formed in systems such as diethylzinc water, alcohol and primary or secondary amine, exhibiting high activity for the homopolymerisation of propylene oxide, were not effective for the copolymerisation of propylene oxide and carbon disulphide [248],... 

The copolymerisation of propylene oxide and sulphur dioxide in the presence of diethylzinc has been found [251] to produce poly(propylene ether-sulphite) (Table 9.4). However, the content of propylene sulphite units in the resulting... 

Explain why propylene carbonate undergoes relatively easily coordination copolymerisation with propylene oxide but hardly undergoes homopolymerisation at moderate temperature. 

Copolymerisation of benzonitrile and propylene oxide with n-butyllithium . ... 

One of the older methods to obtain macromers is to add very small quantities of a monomer having a double bond and a polymerisable epoxy group in the same structure to propylene oxide, during the anionic polymerisation. A typical example of such a kind of monomer is allyl glycidyl ether. This monomer copolymerises anionically with PO, giving polyethers with small quantities of lateral double bonds (reaction 6.10). 

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