Copolymerisation isotacticity

Recent developments in catalyst design have offered more sophisticated catalyst structures with even better copolymerisation ability. Me2Si(Me-Benz(e)Ind)2ZrCl2 is an example of such a catalyst [57, 58]. This catalyst, as mentioned earlier, was originally designed for polymerisation of isotactic polypropene, but it also shows a very high comonomer response in ethene polymerisation [51]. 

Palladium-based catalysts bearing chiral ligands have also been found to be capable of the stereospecific copolymerisation of allylbenzene [492] and its derivatives [493] with carbon monoxide the formed copolymers appeared to be of an alternating, isotactic structure. 

However, when (5,5)-3,3 -(2,3-butanediol)-2,2 -bipyridine or (/ )-3,3 -(l, 2-propanediol) -2,2 -bipyridine was used as the ligand [125], copolymers were obtained that had a higher content of isotactic triads. An effective control towards the isospecificity of copolymerisation (<98 % isotacticity in the copolymer) is fulfilled for the copolymerisation of ring-substituted styrene such as p-t-butylstyrene and carbon monoxide with catalysts containing cationic methylpalladium species [117] ... 

A valuable ligand for the highly isotactic alternating copolymerisation of styrene and / -methylstyrene with carbon monoxide appeared to be Ch-symmet-ric (4S, 4,iS)-(-)-4,4,5,5,-tetrahydro-4,4,-bis(l-methylethyl)-2,2 -bioxazole coordinated to Pd(II) in the cationic complex [135] ... 

This copolymerisation run at room temperature and under low carbon monoxide pressure (1-4 atm) yields highly isotactic optically active polymers. 

The copolymerisation of ketene and acetaldehyde was carried out with ethyl-zinc diphenylamide as the catalyst. It was found to yield an alternating copolymer [scheme (43)], the respective polyester of highly isotactic structure (Table 9.3) [279] ... 

The study of propylene and butane-1 copolymerisation by TiCl3 and A1(C2H5)3 heterogeneous catalysts [72] indicates the presence of AC, which differ in forming isotactic structures. However, there is still an open-ended question are there a different number of groups (types) or do their behaviour characteristics change during the reaction ... 

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