Polymerization stereochemistry

On the other hand, the similarity of 2-(2-pyridylJpropene and 2-vinyl pyridine would lead one to expect a similar oligomerization and polymerization stereochemistry, and this is consistent with the formation of single stereoisomers in the oligomerization of both monomers in the presence of Li ion. Crystallographic studies on a single crystal of [14] are presently carried out in order to resolve this question. 

Our research groups have investigated various b/s(thio/oxo phosphinic)diamido yttrium initiators (e.g. complex 5) [36, 54—56]. These complexes show excellent rates for LA ROP and reasonable control polymerization control is improved in the presence of exogenous alcohol. We have shown that the nuclearity of the initiator has an important influence over polymerization stereochemistry, with a mononuclear complex enabling high degrees of heteroselectivity (Fig. 12). 

The radical polymerization stereochemistry of TrMA is strongly affected by monomer concentration, reaction temperature, and solvent. A lower concentration and a higher temperature lead to a higher isotacticity of the products, and... 

The stereochemistry of 2F4F2PyMA (47) polymerization was also investigated.The optically pure (+)-2F4F2PyMA ([oi]365 +28°) afforded polymers with a relatively low mm content and a low optical activity either by the anionic polymerization with DPEDA-Li inTHF at-78 °C (mm/mr/rr= 70/30/-0, [oi]365 -82°) or by the radical polymerization in toluene using (i-PrOCOO)2 at 40 °C (mm/mr/rr= 54/27/19, [a]365 -2°). The monomer design of 2F4F2PyMA was not as effective as that of PPyoTMA in controlling polymerization stereochemistry. 

When the polymerization stereochemistry is preserved then the mirror approach (reaction a ) will always lead to the formation the isotactic... 

Polymerization observed (including living/controlled polymerization stereochemistry determined (a) [70-741 (b) [4, 75, 76]... 

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