Abstract
AbstractThe cationic polymerizations of dimethyl‐1,3‐butadienes with various catalysts in methylene chloride and toluene have been investigated. The activity of catalysts decreased in the order WCl6 > AcClO4 > SnCl4·TCA > BF3OEt2. The homopolymerization rate of dimethyl‐1,3‐butadienes with WCl6, AcClO4, and SnCl4·TCA decreased in the order 1,3‐dimethyl‐1,3‐butadiene > 2,3‐dimethyl‐1,3‐butadiene > 1,2‐dimethyl‐1,3‐butadiene > 2,4‐hexadiene. The polymers prepared with WCl6, SnCl4.TCA, and BF3OEt2 were rubberlike polymers or white powders, whereas those prepared with AcClO4 were oily oligomers. The 1,4‐propagation increased in the order 1,2‐dimethyl‐1,3‐butadiene < 1,3‐dimethyl‐1,3‐butadiene < 2,3‐dimethyl‐1,3‐butadiene < 2,4‐hexadiene. This order may indicate that the steric effect of methyl group determine primarily the microstructure of the polymer. The relative reactivity of dimethyl‐1,3‐butadienes toward a styryl cation decreased in the order 1,3‐dimethyl‐1,3‐butadiene > 1,2‐dimethyl‐1,3‐butadiene > 2,3‐dimethyl‐1,3‐butadiene > 2,4‐hexadiene. This order may be explained in terms of the stability of the resulting allylic cation.
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