Allyl formate, cationic polymerization

The formation of the unreactive allylic ion causes growth termination of cationically polymerizing 2-methylpropene chains [108]... 

Kennedy et al. used living cationic polymerization from a tricumyl initiator to prepare an allyl-terminated 3-arm star of pIB, followed by hydroboration/oxida-tion to generate hydroxy chain ends which were esterified with 2-bromoisobutyryl bromide to generate the ATRP trifunctional macroinitiator (Scheme 58) [354]. They subsequently carried out ATRP of MMA in toluene using the Cu(I)/N-( -pentyl)2-pyridylmethanimine catalyst system with the addition of Cu° powder [242] to maintain a sufficient concentration of active Cu(I) [354]. Macroinitiators of Mn=9200 and 15,000 were prepared and both had narrow molecular weight distributions (Mw/Mn=1.15 and 1.09, respectively). The formation of block copoly-... 

Cationic polymerizations of allyl esters require further investigation. Schild-knecht [7] mentions the polymerization of allyl acetate and of allyl formate in benzene solution upon heating the solution with 6% of benzenediazonium fluoroborate under nitrogen at 200°C in sealed tubes. The solid products melt at about 190°C (d) and are soluble in benzene and insoluble in methanol. 

Method of synthesis cationic polymerization of high purity Isobutylene and isoprene is used to produce butyl rubber in the presence of complex systems of catalysts polymerization is terminated by irreversible destruction of the propagating carbenium ion by the collapse of the ion pair, by hydrogen abstraction from the comonomer, by formation of stable allylic carbenium ions, or by reaction with nucleophilic species such as alcohols or amines ... 

Carbozirconation. The presence of MAO is essential for the reaction of alkynes with the allylic zirconocene chlorides derived fixim allenes. The Lewis acid presumably enhances the carbozirconation of alkynes by promoting formation of cationic Zr species in the same manner as during the polymerization of a-olefins. 

Polymerizations initiated via addition-fragmentation reactions can also be classified as an initiation process involving radicalic species. The principle of this class of reactions consists in the reaction of a photolytically formed radical with an allyl-onium salt generating a radical cation intermediate. These reactive species undergo a fragmentation giving rise to the formation of initiating cations. 

However this assignment could be questionable. It seems more likely that the 312-314nm band is a result of the cation-solvated contact ion pair for these systems particularly at the low concentrations needed for UV. Furthermore their molecular weight data for BuLi/TMEDA mixtures are not consistent with a stoichiometric 1 2 complex used to explain initiation efficiency. Also it is doubtful that the change from butyl to allyl would lead to essentially complete formation of the 1 2 complex used to explain polymerization activity. 

Suitable salts were those of perchloric acid or, preferably, of hexafluorophosphoric acid." " Experiments carried out with bromine-terminated polystyrene or polybutadiene gave a rapid precipitation of silver bromide even at low temperatures, due to the resonance stabilization of the benzylic or the allylic carbenium ions thus generated. The efficiency of block copolymer formation was found to be determined by factors such as the structure of the carbenium ion, the nature of the gegenion, the experimental conditions and, of course, the nature of the second monomer. Under carefully chosen conditions, THF could be polymerized to form living cationic block copolymers... 

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