Cationic polymerization of 1‐ethoxy‐1,3‐butadiene

Abstract

cis‐ and trans‐1‐Ethoxy‐1,3‐butadienes were polymerized by a variety of cationic agents in various solvents at −78°C. The trans ether, which is the more stable isomer, was found to have greater polymerizability than the cis ether. The trans monomer gave polymers predominantly of the trans‐1,4 type, whereas the cis monomer showed a tendency toward the formation of polymers having the microstructure of the 1,2 type. It was concluded that, in the cis ether, the carbon atom which is the most vulnerable to the attack of carbonium ions is the one at the 2‐position, whereas, in the case of the trans isomer, the terminal 4‐carbon is the most reactive center. The conclusion was confirmed from the results of acetal addition reaction catalyzed by boron trifluoride etherate. The marked contrast in the mode of reaction of the two isomeric ethers toward carbonium ions was interpreted in terms of the difference in the degree of bonding in the transition state.

Controlled Cationic Polymerization of 1‐Methoxy‐1,3‐Butadiene: Long‐Lived Species‐Mediated Reaction and Control over Microstructure with Weak Lewis Bases

“…The peaks assigned to the structure derived from the 2,1‐addition reaction (peaks k, l , and l′ ) were also observed; however, their integral ratios were much smaller than those of the peaks of the aforementioned structures. A very small amount (∼10%) of the cis ‐isomer in the employed monomer reagent is most likely responsible for the generation of the 2,1‐addition structure, as previously reported for the polymerization of a mixture of trans ‐ and cis ‐1‐ethoxy‐1,3‐butadiene . Therefore, the microstructure analysis suggests that the propagation reaction primarily occurred through the addition of a monomer at the 4‐position to the carbocationic species, which has a resonance structure.…”

“…A very small amount (10%) of the cis-isomer in the employed monomer reagent 18 is most likely responsible for the generation of the 2,1-addition structure, as previously reported for the polymerization of a mixture of trans-and cis-1-ethoxy-1,3-butadiene. 17 Therefore, the microstructure analysis suggests that the propagation reaction primarily occurred through the addition of a monomer at the 4-position to the carbocationic species, which has a resonance structure. The preferential formation of the 4,1structure over the 4,3-structure is due to the nature of the propagating carbocation.…”

“…However, the carbocation derived from the attack on the 4‐position has a conjugated structure. 1‐Alkoxy‐1,3‐butadienes have been reported to yield polymers through cationic mechanisms, but controlled polymerization has never been achieved …”

Ab Initio and Experimental Studies on the Hetero-Diels−Alder and Cheletropic Additions of Sulfur Dioxide to (E)-1-Methoxybutadiene: A Mechanism Involving Three Molecules of SO2

“…Alternatively, the relative concentration of complexes 1 •SO 2 in equilibrium with 1 + SO 2 might be too low to be detected by IR spectroscopy (see below). UV/vis measurements were not found useful as our experimental device did not allow us to cool the system at temperatures lower than −25 °C (above this temperature, sulfur dioxide initiates diene polymerization, , see Scheme ). Ab initio calculations have been applied to determine the structures of these complexes.…”

Structure and reactivity in cationic polymerization of butadiene derivatives. IV. 1‐alkoxybutadienes

“…It was reported that the poly(1-EOBD) obtained by cationic polymerization was insoluble in chloroform because of partial crosslinking, and that the proportion of trans-1,4-structure was determined by infrared spectroscopy to be 75-90%. 4 The reason why the poly(1-EOBD) was insoluble in chloroform as reported seems to be high catalyst concentrations and long polymerization times. When the catalyst concentration is lower and the polymerization time is shorter, as in the present study, the poly(1-EOBD) formed is soluble in most organic solvents.…”