Cationic ring-opening polymerization of 2-isopropenyl-4-methylene-1,3-dioxolane

Preparation and cationic ring-opening polymerization of 2-isopropenyl-4-methylene-1,3-dioxolane ( VI ) was performed. Unsaturated cyclic acetal VI was prepared by dehydrochlorination of 2-isopropenyl-4-chloromethyl-1,3-dioxolane, which was easily obtained from methacrolein and epichlorohydrin, with sodium methoxide at ambient temperature. The cationic polymerization of VI with BF₃OEt₂ or CF₃SO₃H at ?78°C afforded only crosslinked polymers, whereas the polymerization by CH₃SO₃H gave soluble poly(keto-ether) which consisted of units VII containing an isopropenyl group in the side chain and units VIII containing a carbon-carbon double bond in the main chain. The reaction of VI with ethanethiol in the presence of protic acid was also carried out as a model reaction of the polymerization. The reaction initiated by the addition of proton to the 4-methylene group of VI , and quantitative ring-opening isomerization followed by the addition of ethanethiol afforded acyclic ketone IX and X . On the basis of the model reaction, the polymerization mechanism is also discussed. © 1993 John Wiley & Sons, Inc.     

Novel photoinitiated cationic copolymerizations of 4-methylene-2-phenyl-1,3-dioxolane

Photoinitiated polymerization of 4-methylene-2-phenyl-1,3-dioxolane ( 1 ) was carried out using either tris (4-methylphenyl) sulfonium hexafluoroantimonate or 4-decyloxyphenyl phenyliodonium hexafluoroantimonate as initiators. ¹H-NMR analyses confirmed exclusive ring-opening while DSC and SEC were used to determine the glass transition temperatures (T_gs) and molecular weights, respectively. Photoinitiated cationic copolymerizations of 1 were investigated with several acyclic and cyclic monomers. Copolymerization of 1 with vinyl ethers and a spiroorthoester resulted in copolymers whose thermal properties were dependent on comonomer ratios. Copolymers of 1 and dihydrofuran or dihydropyran afforded soluble polymers with T_gs significantly higher than the homopolymer of 1 . © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2207–2219, 1997     

Cationic copolymerization of 2-methylene-5,5-dimethyl-1,3-dioxane with 2-methylene-1,3-dioxolane and 2-methylene-1,3-dioxane

Copolymers of the cyclic ketene acetals, 2-methylene-5,5-dimethyl-1,3-dioxane, 3 , (M₁) with 2-methylene-1,3-dioxolane, 4 , (M₂) or 2-methylene-1,3-dioxane, 5 , (M₂), were synthesized by cationic copolymerization. An experimental method was designed to study the reactivity of these very reactive and extremely acid sensitive cyclic ketene acetal monomers. The reactivity ratios, calculated using a computer program based on a nonlinear minimization algorithm, were r₁ = 6.36 and r₂ = 1.25 for the copolymerization of 3 with 4 , and r₁ = 1.56 and r₂ = 1.42 for the copolymerization of 3 with 5. FTIR and ¹H-NMR spectra when combined with the values of r₁ and r₂ showed that these copolymers were formed by a cationic 1,2-polymerization (ring-retained) route. Furthermore the tendency existed to form very short blocks of M₁ or M₂ within the copolymers. Cationic copolymerization of cyclic ketene acetals have the potential to be used for synthesis of novel polymers. © 1996 John Wiley & Sons, Inc.     

Cationic polymerizations of substituted 2-methylene-1,3-dioxocyclic acetals, 2-methylene-1,3-dithiolane and copolymerization of 2-methylene-1,3-dithiolane with 4-(t-butyl)-2-methylene-1,3-dioxolane1

Carbon black-supported sulfuric acid or BF₃·Et₂O-initiated polymerizations of 2-methylene-4,4,5,5-tetramethyl-1,3-dioxolane (1), 2-methylene-4-phenyl-1,3-dioxolane (2), and 2-methylene-4-isopropyl-5,5-dimethyl-1,3-dioxane (3) were performed. 1,2-Vinyl addition homopolymers of 1–3 were produced using carbon black-supported H₂SO₄ initiation at temperatures from 0°C to 60°C whereas both ring-opened and 1,2-vinyl structural units were present in the polymers using BF₃·Et₂O as an initiator. Cationic polymerizations of 2-methylene-1,3-dithiolane (4) and copolymerization of 4 with 2-methylene-4-(t-butyl)-1,3-dioxolane (5) were initiated with either carbon black-sulfuric acid or BF₃·Et₂O. Insoluble 1,2-vinyl addition homopolymers of 4 were obtained upon initiation with the supported acid or BF₃·Et₂O. A soluble copolymer of 2-methylene-1,3-dithiolane (4) and 4-(t-butyl)-2-methylene-1,3-dioxolane (5) was obtained upon BF₃·Et₂O initiation. This copolymer is composed of three structural units: a ring-opened dithioester unit, a 1,2-vinyl-polymerized 1,3-dithiolane unit, and a 1,2-vinyl polymerized 4-(t-butyl)-1,3-dioxolane unit. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2823–2840, 1999     

Copolymerization of 2-methylene-4-phenyl-1,3-dioxolane with electrophilic vinyl monomers through zwitterionic mechanism

Spontaneous copolymerization of cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( I ) with common electrophilic vinyl monomers, such as methyl α-cyanoacrylate (MCA), acrylonitrile (AN), and methyl methacrylate (MMA) were investigated to further explore zwitterion polymerization method with cyclic ketene acetals. In the reaction of I with MCA and AN, spontaneous copolymerization took place at ambient temperature. The copolymers of I with MCA gave low molecular weight polymers, but copolymers obtained with I and AN were high molecular weight polymers. In the reaction of I and MMA, high molecular weight copolymer was obtained only at temperatures above 80°C. Thus, obtained polymers were not the alternating copolymers and possessed high I content in all the cases. From the above results, macrozwitterionic mechanism was suggested as discussed.     

Investigation on radical polymerization of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines

The reaction of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines with benzoyl peroxide (acceptor radical) and with N-ethylmaleimide (acceptor) was investigated. It was shown that benzoyl peroxide adds to monomers 1a and 1b , giving the corresponding linear diester amides 1a and 1b respectively. The oxazolidine 1c adds benzoyl peroxide, without ring opening, by addition to the exomethylene group. Together with N-ethylmaleimide the oxazolidines 1a or 1b produce deep-colored charge transfer complexes, resulting in high molecular poly-N-ethylmaleimides probably via a radical mechanism. The 1,3-dioxolanes 2a and 2b were radically polymerized to produce polyacetals by vinyl polymerization. 2c was polymerized to produce randomly containing acetal units and ester units. The mechanism of polymerization of 2e is complex, affording polymers of nonuniform character. 2-Methylene-4-phenyl-1,3-dioxolane polymerization leads to polyester as the main structure, and to a lesser degree polyacetal structures. The chemical structures of the polymers were confirmed by NMR spectra and elemental analysis. © 1996 John Wiley & Sons, Inc.     

Study on copolymerization behavior of 2-substituted 4-methylene-1,3-dioxolane with maleic anhydride and acrylonitrile

Copolymerizations of 4-methylene-2-styryl-1,3-dioxolane ( 1 ) and 4-methylene-2-methyl-2-styryl-1,3-dioxolane ( 2 ) with electron-deficient monomers, such as maleic anhydride (MA) and acrylonitrile (AN) were investigated. Only homopolymer of 1 was obtained from the copolymerization of 1 with MA in the presence or absence of AIBN. The copolymerization of 1 and AN with AIBN as initiator gave a copolymer consisting of three kinds of repeating units. Reaction of 2 with MA gave a crystalline product with and without AIBN present. A nine-membered ring structure is proposed for this product based on its IR, UV, proton and ¹³C-NMR spectra, as well as elemental analysis. No polymer was obtained from the copolymerization of 2 and AN with or without AIBN initiator. Based on the structures of the products obtained from the copolymerization, a number of polymerization mechanisms are proposed. © 1996 John Wiley & Sons, Inc.     

Preparation and radical ring-opening polymerization of 2-substituted-4-methylene-1,3-dioxolanes

2-Methyl-2-phenyl-4-methylene-1,3-dioxolane ( IIa ), 2-ethyl-2-phenyl-4-methylene-1,3-dioxolane ( IIb ), 2-phenyl-2-(n-propyl)-4-methylene-1,3-dioxolane ( IIc ), 2-phenyl-2-(i-propyl)-4-methylene-1,3-dioxolane ( IId ), 2-(n-heptyl)-2-phenyl-4-methylene-1,3-dioxolane ( IIe ), 2-methyl-2-(2-naphthyl)-4-methylene-1,3-dioxolane ( IIf ), and 2,2-diphenyl-4-methylene-1,3-dioxolane ( IIg ) were prepared and polymerized in the presence of a radical initiator. IIa–IIf were found to undergo vinyl polymerization with ring-opening reaction accompanying the elimination of ketone groups in bulk. IIg was found to undergo the quantitative ring-opening reaction accompanying the elimination of benzophenone in solution to obtain polyketone without any side reaction.