Stereoregularity of poly(α‐methylvinyl alkyl ether)s determined by ¹H‐ and ¹³C‐NMR spectroscopy

Abstract

α‐Methylvinyl methyl ether, ethyl ether, and isobutyl ether were polymerized under various polymerization conditions and the structure of the polymers was determined by 1H‐ and 13C‐NMR spectroscopy. α‐Methyl and β‐methylene carbon spectra of poly(α‐methylvinyl isobutyl ether) showed splitting and were analyzed by triad and tetrad sequences. β‐Methylene carbon spectra of poly(α‐methylvinyl ethyl ether) also showed splitting. When Eu(fod)3 was added, α‐methyl and methoxy proton spectra in benzene of poly(α‐methylvinyl methyl ether) showed splitting assigned to triad tacticities. All the polymers obtained in polar solvents exhibited an increase in syndiotacticity. The polymerization mechanism is discussed.

Copolymers of Isopropenyl Alkyl Ethers with Fluorinated Acrylates and Fluoroacrylates: Influence of Fluorine on Their Thermal, Photochemical, and Hydrolytic Stability

“…Hydrolytic Stability. The homopolymers of low-MW isopropenyl ethers are reported to poorly withstand acidic conditions, , promoting the cleavage of the ether bond with the formation of a relatively stable tertiary carbocation intermediate. The presence of bulky alkoxy side chains, as in BPE, had been anticipated to possibly reduce such hydrolytic sensitivity.…”

“…Introduction of an electron-donating alkyl group at the α-carbon generally increases the reactivity of alkyl vinyl ethers toward electrophiles, although excess steric hindrance can result in the opposite effect. Indeed, methyl isopropenyl ether has been polymerized in fair to good yields with cationic initiators even in relatively mild conditions, , whereas higher alkenyl ether (AE) homologues such as butyl and propyl isopropenyl ether are reported to yield lower MW products . However, the intrinsic higher reactivity of these electron-rich but sterically crowded AE toward electrophilic species is preserved, as shown by their higher reactivity in copolymerization experiments with unsubstituted vinyl ethers, where the steric hindrance is released due to comonomer alternation …”

Poly(Vinyl Ethers)

“…With both strong and weak initiators and independent of the polarity of the solvent used, they give polymers with syndiotactic structures [8].…”

Controlled cationic alternating copolymerization of various enol ethers and benzaldehyde derivatives: Effects of enol ether structures

“…In fact, the alkyl substituent on the double bond of an enol ether greatly affects its polymerizability and behavior even in cationic homopolymerization. For example, the living cationic polymerization of α‐methyl VEs or β‐methyl VEs was achieved only at temperatures much lower than those for VEs due to frequent side reactions . Cyclic enol ethers, β‐substituted VE analogues, have distinct polymerization reactivities compared with their acyclic counterparts.…”

“…For example, the living cationic polymerization of a-methyl VEs or b-methyl VEs was achieved only at temperatures much lower than those for VEs due to frequent side reactions. [6][7][8][9][10][11][12][13][14][15][16] Cyclic enol ethers, b-substituted VE analogues, have distinct polymerization reactivities compared with their acyclic counterparts. Such uniqueness in polymerizability is partially attributable to the ring strain of the monomers in addition to their steric hindrance.…”