Reactivity of metal-containing monomers

Thermal conversion of cobalt(II) maleate, CoC₄H₂O₄2H₂O, (1) at 340–370 °C was studied. The composition of the products of pyrolysis was determined. The major solid-phase product of decomposition consists of nano-sized particles of CoO (sizes vary within narrow limits) stabilized by the polymeric matrix. Thermal conversions of Co^II maleate involve dehydration, polymerization of dehydrated monomers, and decarboxylation of the resulting polymer.     

Telomerization of acrylic monomers with iodoform

Conclusions Together with dimethylformamide, iron pentacarbonyl initiates the telomerization of acrylonitrile, methyl acrylate, and methyl methacrylate with iodoform, resulting in the formation of telomeric homologs of the series CHI₂(CH₂CRI)_nR and CHI₂(CH₂CHR)_nR (n=1, 2; R=H, CH₃; R=CN, COOCH₃).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2284–2287, October, 1985.     

Copolymerization of fluorinated monomers with nonfluorinated monomers. Reactivity and mechanisms

The copolymerization of two monomers usually leads to random copolymers except when one of both bears an electron-acceptor group and the other one has an electron-donor group. Many copolymers are commercially available, mainly in the series of hydrogenated monomers (S.M.A., GANTREZ, MALIALIM resins). The field of fluorinated copolymers is very interesting because of the strong electron-acceptor behaviour of the fluorine atoms and more generally of halogenated atoms. Thus, after HALAR (CTFE^a)-ethylene), TEFZEL (TFE-ethylene) and AFLAS (TFE^b)-propylene) resins, a new series of resins have been produced (copolymers of CTFE and vinyl ethers commercialized by ASAHI Corp.). So it can be considered that ACCEPTOR-DONOR copolymerization with fluorinated monomers is one of the most important applications of that kind of research. After reminding the main mechanisms of that reaction (homopolymerization of charge transfer complex and copolymerization of free monomers), it will be discussed about the mechanism in some examples (CTFE-vinyl ethers and other pairs of monomers). Then it will be explained how cotelomerization has provided new data to prefer a copolymerization mechanism by free monomers.     

Living polymerizations of acrylic monomers with aluminioporphyrin

Aluminioporphyrin was found to be an excellent initiator for the living polymerizations of methacrylates, acrylates, and methacrylonitrile. Porphinatoaluminium thiolate and enolate were effective in the dark, different from methylporphinatoaluminium which requires irradiation by visible light. The addition of pyridine was necessary for the polymerization of methacrylonitrile, which was accelerated by visible light. By using the living polymer of methyl methacrylate as initiator, block copolymers from acrylic monomers could be synthesized. A system composed of aluminioporphyrin and trialkylaluminium was found highly active for the polymerization of methacrylates.     

Stereocontrol in radical polymerization of acrylic monomers

A clear effect of Lewis acids, such. as scandium trifluoromethanesulfonate [Sc(OTf)₃], on stereocontrol during the radical polymerization of a designed monomer, benzyl α-(methoxymethyl)acrylate was found. This Lewis acid also influenced the stereochemistry in the radical polymerization of methyl methacrylate giving a less syndiotactic and more isotactic polymer, although many Lewis acids were not effective. A catalytic amount of Lewis acids, such as Y(OTf)₃ and Yb(OTf)₃, also significantly enhanced isotactic-specificity during the radical polymerization of acrylamide and its derivatives, N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide. Obvious solvent and temperature effects on tacticity were observed in these polymerizations, and poly(NIPAM) with >80% triad isotactic content has been obtained in the presence of Lewis acids.     

Ternary microemulsions of vinylic and acrylic monomers

Ternary systems consisting of sodium dodecyl sulfate (SDS) as surfactant, water and several vinyl and acrylic monomers [vinyl acetate (VAc), acrylonitrile (ACN), ethyl acrylate (EtA), butyl acrylate (BuA), 2-ethylhexyl acrylate (EHA), methyl methacrylate (MMA), butyl methacrylate (MMB) and styrene (St)] were studied. The solubilization of monomer in aqueous solutions of SDS was found to be dependent on its structure and concentration. The molar specific solubility was observed to decrease with hydrophobicity and increase with polarity of monomer, that is, it was lowest for St, EHA and highest for MMA, EtA. The NMR and fluorescence studies indicate that solubilization occurred at a different domain of the interfacial layer. The hydrophobic monomers are solubilized toward the hydrocarbon interior of the micelles whereas the hydrophilic ones, toward the hydrated tail of the surfactant. The penetration of monomers into the oil-in-water interface is limited because the screening of charged ions of emulsifier is not operative. A relationship between the persulfate initiator decomposition rate and the lability of the α-hydrogen linked to the substituted carbon of the double bond was established. The initiator productivity was the highest for MMA (lacking such α-hydrogen) and the lowest for VAc and St, the monomers in which the C-H_α bond is the most reactive.     

Wavelength dependence of laser polymerization of acrylic monomers

Photopolymerization of multifunctional acrylic monomers using excimer and Nd: YAG lasers operated at five different UV wavelengths is reported. The effects of different wavelengths on the surface and bulk cure both in air and under argon are investigated and discussed.     

Light-induced polymerization of new highly reactive acrylic monomers

Acrylic monomers containing an oxetane, dioxolane, oxazolidone or carbonate group in their structural unit have been shown to copolymerize rapidly and extensively with a polyurethane-diacrylate, upon UV radiation. For the most reactive resin, 50% conversion was reached within 3 ms of exposure to a medium-pressure mercury lamp. The kinetics of these ultrafast polymerizations was studied quantitatively by infrared spectroscopy. The rate of polymerization, photosensitivity, and amount of residual acrylate in the cured polymer were determined for the various monomers studied, and compared to the values obtained with conventional mono-, di-, and triacrylates. The functional group introduced into the monomer unit was shown to have a drastic effect on both the reactivity and the physical characteristics of the photocrosslinked polymer. Soft and highly flexible low-modulus polymers were produced with the oxetane, dioxolane, and chlorinated monomers, while the carbonate-acrylate compounds lead to hard and glassy materials. © 1993 John Wiley & Sons, Inc.     

The wetting behavior of grafted hydrophilic acrylic monomers

The wetting behavior of vapor phase photografted hydrophilic acrylic monomers was evaluated by the three most commonly employed techniques, i.e., the captive bubble, the sessile drop, and the Wilhelmy plate technique. The measured contact angles and the overall wetting behavior were discussed in light of the non-ideal nature of these surfaces.It was found that the peculiar nature of hydrophilic grafted surfaces is carefully reflected in the experimentally measurable contact angles. While in the case of the captive bubble the hydrophilic and rough nature of these coatings prevent the bubble-surface contact, in the case of the sessile drop the measured contact angles follow the behavior predicted by contact angle hysteresis theories. Wilhelmy plate measurements, performed as sequential scanning loops, show velocity-dependent effects which are linked to the composition, morphology and mobility of the grafted surfaces.     

Reactivity of oxetane monomers in photoinitiated cationic polymerization

Studies of the onium salt photoinitiated cationic ring‐opening polymerizations of various 3,3‐disubstituted oxetane monomers have been conducted with real‐time infrared spectroscopy and optical pyrometry. The polymerizations of these monomers are typified by an extended induction period that has been attributed to the presence of a long‐lived tertiary oxonium ion intermediate formed by the reaction of the initially formed secondary oxonium ion with the cyclic ether monomer. Because the extended induction period in the photopolymerization of these monomers renders oxetane monomers of limited value for many applications, methods have been sought for its minimization or elimination. Three general methods have been found effective in markedly shortening the induction period: (1) carrying out the photopolymerizations at higher temperatures, (2) copolymerizing with more reactive epoxide monomers, and (3) using free‐radical photoinitiators as synergists. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3205–3220, 2005     

Surface modification of polyolefins by photografting of acrylic monomers

High-speed surface modification of polypropylene (PP) and polyethylene (PE) films has been achieved by liquid phase photograft polymerisation of acrylic acid (AA) and hydroxypropyl acrylate (HPA). Benzophenone was used as photoinitiator to generate polymer radicals at the surface of the polyolefin film. The grafting reaction was carried out in aqueous solution or with the neat monomer, which was laminated between two PP films, in the presence of air. Under the intense illumination of a UV-curing line, acrylic acid was grafted within seconds to polypropylene films or fabrics, which were thus made hydrophilic. Direct evidence of surface grafting was obtained through infrared spectroscopy analysis and surface energy measurements. This continuous photografting process proved to be very efficient to improve the adhesion of UV-cured acrylate coatings on polyolefin-made materials.     

Copolymerization of N-vinylpyrrolidone with acrylic monomers in vitrifying solutions

The low-temperature copolymerization of N-vinylpyrrolidone with acrylic monomers (acrylic acid, acrylamide, and methyl acrylate) in vitrifying solutions in ethanol and DMF has been studied. It has been shown that the copolymerization proceeds after transition of preliminarily γ-irradiated at 77 K samples from the solid glassy state to a supercooled liquid. Experimental conditions that ensure formation of alternating and random block copolymers have been established. The composition of copolymers is determined by the relative mobility and initial ratio of comonomers in solution.     

Linear polymers of acrylic monomers containing an acetylenic moiety

1-Acryloxy-2-butyne and 1-methacryloxy-2-butyne were synthesized and polymerized by means of anionic initiators to soluble linear polymers containing acetylenic bonds in the pendant side chains. In contrast, insoluble, crosslinked polymers were formed when cationic and radical initiators were used. The unpolymerized acetylenic bonds in the resulting linear polymers were shown to be present by infrared spectroscopic methods and by the following post-reactions of these bonds: (1) the thermal- and radical-initiated crosslinking of the linear polymers through the acetylenic bonds; (2) the post-bromination of the acetylenic bonds; and (3) the reaction of decaborane with the acetylenic bonds. The anionic copolymerization of both monomers with a number of selected monomers was performed and the copolymer reactivity ratios for several of the comonomer pairs were determined. Dibromination of the linear polymers affords self-extinguishing polymers with apparently good hydrolytic stability. Decarbonation of the linear polymers yields soluble polymers which do not soften up to 300°C. The linear polymers and copolymers, as well as their partially brominated and partially decaboronated products, may be classified as “self-reactive” polymers which yield thermosetting polymers.     

Hybrid composites based on organosilicon monomers and acrylic acids

The formation of hybrid composites in sol-gel systems based on organosilicon monomers and acrylic acids was studied. The composition, properties, structure, and morphology of the products were examined.     

Copolymerization of fluorinated acrylic monomers with p-vinylphenol and hydroxyethyl methacrylate

Copolymers of p-vinylphenol were prepared in bulk with heptafluorobutyl and pentadecafluorooctyl acrylates and trifluoroethyl, hexafluoroisopropyl, heptafluorobutyl, octafluoropentyl and pentadecafluorooctyl methacrylates using azobisisobutyronitrile as the initiator in sealed tubes. Intrinsic viscosities of the copolymers ranged from 0.44 to 1.85. Monomer reactivity ratios for copolymers of trifluoroethyl methacrylate (M₁) were: with hydroxyethyl methacrylate (M₂), r₁ = 0.47, r₂ = 1.0; with methyl methacrylate (M₂), r₁ = 0.82, r₂ = 0.50; with styrene (M₂), r₁ = 0.29, r₂, = 0.20; and with p-vinylphenol (M₂), r₁ = 0.096, r₂ = 1.5. Q and e values of trifluoroethyl methacrylate were 1.30 and 0.92, respectively. Monomer reactivity ratios of octafluoropentyl methacrylate (M₁) were: with styrene (M₂), r₁ = 0.26, r₂ = 0.20; and with p-vinylphenol, r₁ = 0.21, r₂ = 1.5. Q and e values for octafluoropentyl methacrylate were 1.27 and 0.92, respectively. Critical surface tensions of the homopolymers ranged from 17.9 to 14.8 dyn/cm. A copolymer of hexafluoro-i-propyl methacrylate and p-vinylphenol exhibited a critical surface tension of 16.5 dyn/cm.     

HPLC determination of residual monomers released from heat-cured acrylic resins

HPLC was used to examine the leachability of three non-phthalic and four phthalic post-polymerized residual monomers from three commercially available heat-cured acrylic resins. Specimens of equal dimensions were constructed from each brand of material by following the standardized procedure and were stored under three different conditions, namely, distilled water, artificial saliva, and a binary mixture of ethanol/water. The resulting liquids provided samples for analysis by HPLC. Three different experiments were performed for each brand of acrylic and each storage condition in order to examine the effects of parameters, particularly time and temperature. The results obtained from this study suggest that a wide spectrum of residues diffuse out of the three examined acrylic resin materials. The non-phthalic compounds were leached at high concentrations, whereas all the phthalates examined exhibited different degrees of elusion commensurate with the storage condition, brand of material, and type of experiment. It seems that a significant quantity of non-phthalic and phthalic residues diffuse out of the acrylic resin materials examined. The main component extracted was methyl methacrylate, the level of which seems to be time-dependent and decreases for a period of up to 5 days when resins are stored in distilled water at room temperature.     

Frontal polymerization of acrylic monomers for the consolidation of stone

Polymeric products are largely used for consolidation of stone in the field of cultural heritage. Nevertheless, the main problem of polymeric compounds is related to their macromolecular nature, it being difficult for a polymer to penetrate inside the pores which may have a very small diameter. These considerations are the starting points for in situ polymerization. According to this technique, not the pre‐formed polymer, but the monomer is introduced into the stone and it is polymerized in situ in a subsequent step. Frontal polymerization (FP) is a particular technique in which the heat released by the exothermal reaction of monomer to polymer conversion is exploited to promote the formation of a hot traveling front able to propagate and self‐sustain the reaction. In the present work, FP is performed inside the pores of the stone and the results lead to the conclusion that the hot front is still active in the presence of an inorganic material which dissipates partially the heat released during the polymerization. In addition some recent applications of FP are discussed in comparison with the traditional polymerization for the in situ consolidation and protection of stones. Copyright © 2005 John Wiley & Sons, Ltd.     

Molecular‐dynamic simulation of conformations of acrylic monomers

The computer simulation of local dynamics of associates of homologous series of acrylic esters has been developed. It is shown that dynamic behaviour of molecules in associate intrinsically changes in different temperature regions. Solid‐like behaviour is observed at low temperature, liquid‐like at intermediate temperatures and gas‐like behaviour at high temperature. Good correlation is obtained between the energy of intermolecular interactions of associates and melting points of corresponding chemical substances.     

Reactivity ratio of novel acrylic copolymer by NMR spectroscopy

The monomer 4-methylcoumarylacrylate (4-MCA) was synthesized from 7-hydroxy-4-methylcoumarin and characterized by conventional methods. Homo and copolymers of 4-methylcoumarylacrylate and styrene were synthesized with different feed ratios using N,N-dimethylformamide (DMF) as a solvent and 2,2′-azobisisobutyronitrile as an initiator at 70°C.The resulting polymers were characterized by infrared spectroscopy. Copolymer compositions were determined by nuclear magnetic resonance spectroscopy. The monomer reactivity ratios were determined by applying the conventional linearization method of Fineman–Ross and Kelen–Tudos. The reactivity ratios values of 4-methylcoumarylacrylate and styrene obtained from F–R plot are 1.36 and 0.62, respectively, and from K–T plot 1.24 and 0.58, respectively.