Vinyl Ether System Research Articles

Cationic photopolymerization of bisphenol-A-based vinyl ether systems

2,2-Bis{4-[2-(vinyloxy)ethoxy]phenyl}propane (BPA) monomer was synthesized and its cationic photopolymerization with triethyleneglycol divinyl-ether (DVE3) investigated. Real-time FT-IR kinetic investigations showed, in the presence of DVE3 monomer an increase of the photopolymerization rate and of the final vinyl ether double bond conversion. All the formulations investigated gave rise to transparent films characterized by a high gel content (>94%). An increase of Tg values by increasing the BPA content was observed by DSC and DMTA analyses; it was attributed to the rigid bisphenol-A-units introduced within the polymeric network. DMTA analyses showed an increase of the modulus E′ by increasing BPA content. Surface hardness of the cured films was improved by BPA copolymerization.

Conversion of an Arabinose‐Derived Allyl Vinyl Ether System into the Functionalized 4‐Cycloheptenone via Claisen Rearrangement.

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Conversion of an Arabinose-Derived Allyl Vinyl Ether System into the Functionalized 4-Cycloheptenone via Claisen Rearrangement

A large number of natural products display seven‐membered rings as a distinctive structural feature.1 Since they frequently contain both oxygenated functions and stereogenic centers, their synthesi...

Curing kinetics of UV‐initiated cationic photopolymerization of divinyl ether photosensitized by thioxanthone

AbstractPhotodifferential scanning calorimetry was used to investigate the photocuring kinetics of UV‐initiated cationic photopolymerizations of 1,4‐cyclohexane dimethanol divinyl ether (CHVE) monomer with and without a photosensitizer, 2,4‐diethylthioxanthone (DETX), in the presence of a diaryliodonium‐salt photoinitiator. Two kinetics parameters, the rate constant (k) and the order of the initiation reaction (m), were determined for the CHVE system with different amounts of added DETX photosensitizer (0–1 wt %) and at different isothermal temperatures (25–55°C) using an autocatalytic kinetics model. The photosensitized CHVE system exhibited much higher k and m values than did the nonphotosensitized system, which was attributable to the effects of photosensitization. Furthermore, the values of k and m for both CHVE systems increased significantly with increasing isothermal temperature because of a thermal contribution toward increasing the mobility of active species. The addition of DETX lowered the activation energy for the UV‐curable vinyl ether system. The collision factor for the system with DETX was higher than that obtained for the system without DETX, indicating that the reactivity of the former was greater than that of the latter because of the photosensitization effect. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1345–1351, 2005

Near‐infrared spectroscopy investigation of water effects on the cationic photopolymerization of vinyl ether systems

AbstractReal‐time Fourier transform near‐infrared spectroscopy has been used to monitor monomer and water concentrations simultaneously during cationic vinyl ether photopolymerization. The use of near‐infrared peak area methods allows the water content to be conveniently and nondestructively determined in any monomer or polymer for which the water peak has previously been calibrated by gravimetric analysis. Although the shape of the absorption band due to absorbed water in a monomer changes with the quantity of water, the integrated intensity from about 5350 to 4900 cm−1 can be correlated directly to the water concentration, and this region is well removed from the vinyl‐based absorption at approximately 6190 cm−1. This approach provides a highly informative, dynamic technique for examining the influence of moisture on polymerization reactions. Significant differences have been observed in the effects of absorbed water on the cationic photopolymerization kinetics of vinyl ether monomers with or without an OH group. Along with the rapid consumption of water coupled to vinyl ether polymerization, acid‐catalyzed hydrolysis reactions have also been spectroscopically observed, giving rise to the formation of aldehyde groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1985–1998, 2004

Thiol−Ene Photopolymerization Mechanism and Rate Limiting Step Changes for Various Vinyl Functional Group Chemistries

The mechanism and kinetics of thiol−ene photopolymerizations utilizing a tetrafunctional thiol monomer copolymerized with acrylate, norbornene, vinyl ether, and vinyl silazane functionalized ene monomers are successfully modeled and experimentally characterized. Modeling predictions demonstrate that the reaction orders in thiol−ene systems are controlled by the ratio of thiyl radical propagation to chain transfer kinetic parameters (kp/kCT). Ratios of kinetic parameters (kp/kCT) were found to vary significantly with the ene functional group chemistry and to have a dramatic impact on polymerization kinetics. For high ratios of kp/kCT, polymerization rates are first order in thiol functional group concentration and nearly independent of ene functional group concentration. For kp/kCT values near unity, polymerization rates are approximately 1/2 order in both thiol and ene functional group concentrations. When kCT is much greater than kp, polymerization rates are first order in ene functional group concentration and nearly independent of the thiol functional group concentration. In thiol−allyl ether and thiol−acrylate systems, the step growth polymerization rates are first order in thiol functional group concentration (Rp ∝ [SH]). For thiol−norbornene and thiol−vinyl ether systems, polymerizations are nearly 1/2 order in both thiol and ene functional group concentrations (Rp ∝ [SH]1/2[CC]1/2). In thiol−vinyl silazane systems, polymerization rates are approximately first order in ene functional group concentration (Rp ∝ [CC]) and independent of thiol functional group concentration. A theory is proposed which states that the effect of functional group chemistry on kp/kCT is controlled primarily by ene functional group electron density (kp) and carbon radical stability (kCT).

Photopolymerizations of Thiol−Ene Polymers without Photoinitiators

A thiol monomer is shown to copolymerize with vinyl ether, allyl, acrylate, methacrylate, and vinylbenzene monomers. These thiol−ene polymerizations are photoinitiated without the use of photoinitiator molecules. It is seen that the polymerization proceeds more readily when initiatorless samples are irradiated with light centered around 254 nm as compared to 365 nm light. To demonstrate resistance to oxygen inhibition, thin polymer films of 3−15 μm are polymerized while exposed to ambient air. Without photoinitiator molecules present, light is attenuated only by the monomer and polymer. This feature leads to greater penetration of ultraviolet light and allows for the polymerization of extremely thick polymers. Thick cures of up to 25 in. are obtained using a thiol−vinyl ether system.

Cationic photoinitiated copolymerization of 1-propenyl–vinyl ether systems

A kinetic investigation of the photoinitiated cationic copolymerization of 1-propenyl ethers with vinyl ethers monomers was performed by using FT-IR and 1 H-NMR analysis. FT-IR results, obtained in bulk, indicate a higher reactivity of the vinyl ether with respect to the 1-propenyl ether double bond. 1 H-NMR analysis, in CDCl 3 solution, confirms these results which agree with the literature data concerning monofunctional systems. The properties of the UV cured copolymerization products are investigated by DMTA analysis and discussed on the basis of the kinetic investigation results.

Cationic photopolymerization of vinyl ether systems: influence of the presence of hydrogen donor additives

Several alcohols ( n-butanol, 2-propanol, 2-phenyl-2-propanol) and water were added to diethylene-glycol-divinyl-ether (DVE2) or triethylene-glycol-divinyl-ether (DVE3) in order to investigate their influence on the cationic photopolymerization in the presence of triarilsulfonium hexafluorophosfate as photoinitiator. Until 5% w/w concentration, the alcohols do not show any influence on the rate of polymerization, but they increase the final double bond conversion indicating a plasticization effect. Water causes a decrease of the rate of polymerization and an increase of the final double bond conversion. DSC and DMTA analyses show that the presence of the additives decreases the T g of the UV-cured products. The results are interpreted on the basis of a chain transfer reaction involving -OH groups.

Postcure behavior of UV curable materials: A comparison of urethane acrylates with vinyl ether end-capped urethanes.

The study presented here examines the effect of postcure on the mechanical properties of urethane acrylates as compared to vinyl ether functionalized polyurethanes. The vinyl ether systems cure via a cationic mechanism and are, therefore, expected to undergo dark reactions which may lead to noticeable postcure effects. Urethane acrylate systems, on the other hand, are not known to undergo postcuring reactions since these systems polymerize via the free radical mechanism. Recently, however, it has been reported that trapped free radicals exist in irradiated acrylate samples for periods as long as seventy days [1], and that radical entrapment occurs very early in the reaction at conversions as low as 10% [2] . It has also been reported that acrylate unsaturation continues to disappear for several days after irradiation [3]. These findings, important as they are, only reflect the spectroscopic behavior of UV cured acrylates using electron spin resonance and infrared absorption techniques. Although some studies relating mechanical property changes to postcuring of acrylate systems have been reported [4], no clear correlation between these parameters has been identified [5]. The comparative data reported here helps identify the effects and the nature of the postcuring process in both the acrylate and the vinyl ether systems.

The possible role of tropical medicinal preparations in human carcinoma in Africa

It is suggested that apart from aflatoxins, plant medicinal preparations containing active compounds imperatorin, dictamine, marmesin and heraclenin may be responsible for some human cancers in NIgeria and perhaps other parts of Africa. Therefore, in this paper, a hypothesis is put forward that these compounds or their reactive (metabolized) types may form epoxides from the 2,3-furan double bonds which may bind tissue macromolecules, DNA, RNA and protein leading to one of the vital steps of environmental carcinogenesis in mammals. This hypothesis has far reaching implications for, besides the examples given, unanalysed plant preparations are widely used in various parts of Africa within traditional methods of healing. Our observation is based on information we now have about AFB 1 and is not intended to confirm the roles of double bonds in a vinyl ether system of the active compounds.

Alternating copolymerization of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone with styrene and polymerization behavior with vinyloxy compounds

Abstract2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) was found to copolymerize alternatingly with styrene (St). DDQ–isobutyl vinyl ether and DDQ–2‐chloroethyl vinyl ether systems gave homopolymers of vinyl ethers, while DDQ–phenyl vinyl ether and DDQ–vinyl acetate systems gave oligomers containing both monomer units. In the terpolymerization of DDQ, p‐chloranil (pCA), and St, terpolymers obtained were found to have about 50 mole % of St units regardless of monomer feed ratio and DDQ was incorporated much more rapidly into the terpolymer than pCA. The difference in the reactivity of the acceptor monomers could be attributed to that in their electron‐accepting character.

Spontaneous polymerization of the nitroethylene–isobutyl vinyl ether system

AbstractInitiation and propagation mechanisms of the spontaneous polymerization of the system nitroethylene–isobutyl vinyl ether were studied. An equimolar mixture of these two monomers gives white precipitates below room temperature, though they react explosively to give viscous products at higher temperature. The precipitate was found to be composed of a polynitroethylene and a cycloadduct of these two monomers. The isolated cycloadduct product is so reactive that it not only polymerizes itself spontaneously but also initiates the polymerization of nitroethylene. The polymerization of the cycloadduct was revealed to proceed without termination to produce an alternate copolymer of these two monomers. These results indicate that the explosive spontaneous polymerization of this system consists of three elementary reaction processes; (1) cycloaddition reaction between two monomers, (2) anionic polymerization of nitroethylene induced by the cycloadduct, and (3) the living ring‐opening polymerization of the cyclo‐adduct.

Studies on the Metabolites of Aspergillus versicolor (Vuillemin) Tiraboschi

Three new pigments, named versicolorins A, Band C, as metabolites from the mycelium of Aspergillus versicolor have been isolated. Versicolorin A, C18H10O7, is fine orange yellow needles, m.p. 289°C (decomp.), [α]D-354°. It is an anthraquinoid pigment having three hydroxyl groups and a vinyl ether system contained in a five-membered ring. Versicolorin A trimethyl ether was hydrogenated to a dihydro-derivative, and by oxidation gave 3,5-dimethoxyphthalic acid and a hydroxy acid which may be 1,6,8-trirnethoxy-3-hydroxy anthraquinone-2-carboxylic acid. These chemical behavior and NMR data show that versicolorin A probably has the structure of (I). Versicolorin B, C18H12O7, is fine orange yellow needles, m.p., 298°C (decomp.), [α]D-223° Its trimethyl ether is identical with that of dihydroversicolorin A. Therefore, the structure (II) could be assigned to versicolorin B. Versicolorin C, C18H12O7, is orange red needles, m.p.>310°C, [α]D O° Comparison of optical properties, IR and NMR spectra of versicolorin B an...

Analytical Study of Aminoethyl Vinyl Ether System Based on Countercurrent Extraction

Analytical Study of Aminoethyl Vinyl Ether System Based on Countercurrent Extraction