Cationic polymerization of dimethyl‐1,3‐butadienes

Abstract

The 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.

Cationic polymerization of 1,3‐pentadiene I. infrared, 1H‐NMR and 13C‐NMR investigations on the microstructure of poly(1,3‐pentadiene) synthesized with cationic catalysts

“…Asami et al (Refs. 10,11,18,19) were interested in various alkyl-and cnyl-butadienes among which the piperylene whose cationic polymerization was the object of few systematic investigations (Refs. 11,(20)(21)(22)(23).…”

Stereochemistry of Polymerization

“…There is a general tendency toward 1,4-polymerization with trans 1,4 favored over cis 1,4. Cyclization occurs during propagation with the extent of unsaturation in the product varying from about 80% to almost zero depending on initiator, monomer, and reaction conditions [Delfour et al, 2003;Gaylord and Svestka, 1969;Gaylord et al, 1968;Hasegawa and Asami, 1978;Hasegawa et al, 1977].…”