✍ Scribed by Natalia I. Pakuro; Irina V. Zolotareva; Alla G. Kitayner; Elena D. Rogozhkina; Anatoliy L. Izyumnikov; Alexander A. Arest-Yakubovich
No coin nor oath required. For personal study only.
Polymerization of butadiene and isoprene initiated by the hydrocarbon-soluble mixture 2-ethylhexyllithium/2-ethylhexylsodium in toluene was studied. The components of the initiator when taken separately give rise to polymers greatly different in both their molecular weight and microstructure: living polydienes with high 1 ,4-unit content are formed when alkyllithium is used while organosodium initiators produce polymers of high 1,2(3,4)-structure and of low molecular weight due to strong chain transfer to toluene. Polymers obtained with mixed initiators were found to have the same structure as the "sodium" ones, while their molecular weights are either the same as those of the polymers obtained with alkyllithium alone (in the case of butadiene) or decrease gradually with increase of sodium content in the initiator (in the case of isoprene). The calculations performed show that the simple scheme assuming chain propagation through individual lithium and sodium active centres and fast exchange of counter-ions between them cannot explain the results obtained. It is suggested that the true active centres in mixed systems are bimetallic complexes containing both sodium and lithium atoms simultaneously.
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## Abstract Photopolymerizations of __N__‐isopropylacrylamide (NIPAAm) were carried out in water, initiated by 2‐(__N,N__‐diethyldithiocarbamyl)isobutyric acid sodium salt (DTCA‐Na) as water‐soluble initiator under UV irradiation. The first‐order time‐conversion plots showed slowly decreasing slope