Comment on radical polymerization mechanism of vinyl benzoate

Summary The elementary rate constants for the radical polymerization of vinyl acetate and vinyl benzoate have been determined in various aromatic solvents and ethyl acetate. The kp values for vinyl benzoate are larger than those for vinyl acetate in all solvents, although methyl affinities of both monomer were similar. These results show that the poly(vinyl benzoate) radical is more reactive than the poly(vinyl acetate) radical.     

Synthesis of sulfone-modified poly(vinyl alcohol) and its application for permselective membrane of sulfur dioxide

The Michael type addition reaction of poly(vinyl alcohol) (PVA) with a series of vinyl sulfones, namely methyl vinyl sulfone, ethyl vinyl sulfone, and t-butyl vinyl sulfone, was performed with NaOH as catalyst to produce 2-(alkylsulfonyl)ethyl PVA derivatives. The high permselectivity of sulfur dioxide against nitrogen and oxygen was achieved through these sulfone-modified PVA membranes.     

Polymerization and copolymerization of vinyl carbamates and vinyl carbonates

Poly(vinyl carbamates) and poly(vinyl carbonates) of high molecular weight have been obtained by polymerization of the corresponding monomers prepared from vinyl chloroformate. Poly(vinyl carbonates) can also be prepared by chemical modification of poly(vinyl chloroformate) with alcohols and phenols. Copolymerization parameters of phenyl vinyl carbonate with vinyl acetate have been determined in methylene chloride, at 35°C, with dicyclohexyl peroxydicarbonate as initiator.     

Mechanochemical synthesis and characterization of poly(vinyl chloride)-block-poly(vinyl alcohol) copolymers by ultrasonic irradiation

Mechanical degradation and mechanochemical reaction in heterogeneous systems of the solid poly(vinyl chloride)-poly(vinyl alcohol) aqueous solutions have been studied by ultrasonic irradiation at 30 °C. The rate of decrease in the viscosity-average degree of polymerization of the degraded poly(vinyl chloride) was much faster than that of the degraded poly(vinyl alcohol). Mechanochemical reaction occurred by free radicals produced from the chain scissions of both polymers by ultrasonic waves. The copolymer was obtained and the molar ratio of the vinyl chloride and the vinyl alcohol units in its copolymer can be determined. In addition, the changes in the composition of the total block copolymer, the unreacted poly(vinyl chloride), and the unreacted poly(vinyl alcohol) were obtained. Received: 1 October 1998/Revised version: 9 January 1999/Accepted: 13 January 1999     

Photosensitivities and rates of photocrosslinking of poly(vinyl α-cyanocinnamate) and poly(vinyl α-cyanocinnamoxy acetate)

The photosensitivities and the rates of photocrosslinking of poly(vinyl α-cyanocinamate) and poly(vinyl α-cyanocinnamoxyacetate) were investigated. The photocrosslinkings of these polymers proceeded mainly through radical addition, and these polymers showed higher photosensitivities than poly(vinyl cinnamate) and poly(vinyl cinnamoxyacetate), in spite of lower rates of photocrosslinking of the former polymers.     

Reinforcement of liquid ethylene–propylene–dicyclopentadiene copolymer based elastomer with vinyl functionalized multiwalled carbon nanotubes

A methodology for reinforcement of liquid ethylene–propylene–dicyclopentadiene copolymer (liquid‐EPDM) based elastomer with multiwalled carbon nanotubes (MWCNTs) was proposed. Acid‐treated MWCNTs were first reacted with poly(acryloyl chloride) (PACl) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl‐MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl‐MWCNTs were blended with liquid‐EPDM and subjected to co‐curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl‐MWCNTs and the double bonds on liquid‐EPDM. As a result, the vinyl‐MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl‐MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Preparation,glass transition temperature,and δ relaxation effect of poly(vinyl isonicotinate)

Poly(vinyl isonicotinate) was prepared by esterification of poly(vinyl alcohol) with isonicotinoyl chloride in pyridine solution. Poly(vinyl nicotinate) was also prepared. Density, refractive index, and glass transition of the polymers were determined. The low temperature dynamic mechanical properties of poly(vinyl isonicotinate) are characterized by a relaxation effect which is associated with thermally excited motions of the pyridine rings (δ relaxation). The strong displacement of such a phenomenon toward higher temperatures, with respect to poly(vinyl benzoate), is interpreted as due to the elevated polarity of the pyridine ring.     

Ultrasonic attenuation and mobility in polymer solutions and dispersions. Poly(vinyl alcohol) and poly(vinyl acetate)

Summary To obtain informations about molecular processes, poly(vinyl alcohol) solutions and poly(vinyl acetate) solutions and dispersions have been studied by ultrasonic methods in the frequency range from 200 kHz to 150 MHz. The measured excess attenuations are qualitatively discussed in terms of cooperative and local mode motions of the macromolecules. In poly(vinyl alcohol) solutions with different residual vinyl acetate content a mixing of normal and local mode motions has been observed. In poly(vinyl acetate)/toluene solution two discrete relaxation processes have been detected which are probably related to a local mode and a coupling of local and normal mode motions, respectively. The frequency-temperature dependence of the absorption maximum of the poly(vinyl acetate) dispersion follows the WLF relation.     

Toughening of vinyl ester resins by two-dimensional MXene nanosheets

Two-dimensional nanosheets are highly effective tougheners for vinyl ester resins. The toughening effect is related to the high specific surface area and unique two-dimensional planar structure of the nanosheets. In this study, a coupling agent γ-(2,3-epoxypropoxy) propytrimethoxysilane (Kh-560) was used to modify MXene nanosheets (M-MXene) for use in toughening vinyl ester resin. The mechanical properties, including the tensile strength, flexural strength, Young’s modulus and elongation, of neat vinyl ester resin and vinyl ester resin modified with MXene and M-MXene were investigated. The results showed that modification significantly improved the mechanical properties of the vinyl ester resin. The tensile and flexural strengths of the MXene-nanosheet-modified vinyl ester resin were 27.20% and 25.32% higher, respectively, than those of the neat vinyl ester resin. The coupling agent improved the interfacial compatibility between the MXene nanosheets and vinyl ester resin, which resulted in the tensile and flexural strengths of the M-MXene-nanosheet-modified vinyl ester resin being 52.57% and 54.60% higher, respectively, than those of the neat vinyl ester resin for a loading quantity of nanosheets of only 0.04 wt %, which is economically viable. The main mechanisms by which the nanosheets toughen the resin are crack deflection and crack pinning.     

Studies on the preparation and properties of conductive polymers. IX. Using photographic developer to prepare metallized conductive polymer films

Poly(vinyl alcohol) metal chelate solutions were prepared by mixing silver nitrate with solutions of poly(vinyl alchol), and films wee prepared from these solutions. These poly(vinyl alcohol) metal chelate films were reduced by photographic developer. The silver ions in poly(vinyl alcohol) films were reduced to silver on the surface, and conductive polymer films were obtained. © 1996 John Wiley & Sons, Inc.     

Reaktive träger zur immobilisierung von enzymen auf der grundlage von polyvinylalkohol

On the basis of poly(vinyl alcohol) various reactive carriers for the immobilization of enzymes were synthesized. Starting as well from hydrolyzed beads of crosslinked poly(vinylacetate), as from tubes of poly(vinyl acetate-co-ethylene) which have been coated with poly(vinyl alcohol) resp. from poly(vinyl alcohol) containing synthetic pulp reactive carriers were synthesized by reaction with 2-(3-aminophenyl)-1,3-dioxolane followed by diazotization. Furthermore reactive isothiocyanato groups as well as mixed polymeric disulfides with 2-thiopyridine groups were introduced into gels of poly(vinyl alcohol) which were crosslinked with terephthalaldehyde. The immobilization of enzymes was carried out with papain, trypsin, glucose oxidase, and catalase. The properties of the immobilized enzymes were investigated.     

Physicochemical characterization of hydrogels based on polyvinyl alcohol–vinyl acetate blends

Hydrogels made of polyvinyl alcohol–vinyl acetate and its blends with water soluble polymer were studied in terms of swelling behavior, microstructure, and dynamic mechanical properties. Hydrogels prepared by blending polyvinyl alcohol–vinyl acetate with either polyacrylic acid or poly(4‐vinyl pyridine) exhibited a strong pH dependency. When poly(vinyl pyrrolidone) was used for blending, an unusual pH dependency was observed. An increase in the equilibrium water content in all systems resulted in an increase in the freezable water as determined by DSC. Critical point drying led to a striated surface on polyacrylic acid–polyvinyl alcohol–vinyl acetate hydrogels, whereas a porous structure was observed on the freeze‐dried poly(vinyl pyrrolidone)–polyvinyl alcohol–vinyl acetate gels. Hydrogels with elevated storage modulus were obtained when either polyvinyl alcohol–vinyl acetate alone or polyacrylic acid–polyvinyl alcohol–vinyl acetate blends were thermally treated at high temperatures (i.e., 150°C). Low storage modulus was observed for both poly(vinyl pyrrolidone) and poly(4‐vinyl pyridine)‐containing hydrogels. Temperature dependency of storage modulus from 20 to 60°C was observed only for poly(4‐vinyl pyridine)–polyvinyl alcohol–vinyl acetate hydrogels. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3578–3590, 2001     

The in situ polymerization of vinyl chloride in poly(butyl acrylate)

The in situ polymerization of vinyl chloride with poly(butyl acrylate) has been studied. Vinyl chloride was polymerized using a peroxydicarbonate initiator in sealed ampoules in the presence of various weights of poly(butyl acrylate). The products were examined by dynamic mechanical analysis and electron microscopy. It was found that if about 50% or less vinyl chloride was present in the mixture homogeneous blends were formed. If more than 50% vinyl chloride was present the polymerization passed through a two phase region in the three component phase diagram and inhomogeneous blends were formed. If homogeneous blends prepared as above were reswollen with vinyl chloride and the latter polymerized, then homogeneous blends containing more poly(vinyl chloride) could be prepared, avoiding the two phase region. The interaction parameters between vinyl chloride and both poly(vinyl chloride) and poly(butyl acrylate) were estimated using inverse gas chromatography. Using these and an estimate of the polymer/polymer interaction parameter the three component phase diagram could be qualitatively explained.     

Vinyl chloride formation from the thermal degradation of poly(vinyl chloride)

The volatile products from the thermal degradation of poly(vinyl chloride) (PVC) resins and compounds are shown to contain trace amounts of vinyl chloride. Data presented show the effect of temperature and resin type on the amount of vinyl chloride formed. At the maximum temperatures involved in PVC processing which may reach 210°C, vinyl chloride monomer (VCM) evolution amounts to less than 1 ppm (resin basis). A technique employing a thermogravimetric balance and charcoal adsorption of volatiles is described for studying thermal degradation of PVC. The volatiles are analyzed for vinyl chloride by gas chromatography. Peak identity was confirmed by mass spectrometry.     

Radiation-convertible polymers from norbornenyl derivatives. Crosslinking with ionizing radiation

Vinyl polymers with pendant norbornenyl (bicyclo[2.2.1]heptenyl) groups crosslink rapidly on exposure to ionizing radiation. Analysis (according to Charlesby-Pinner theory) of extraction data from an ethylene–vinyl acetate copolymer and the corresponding ethylene–vinyl norbornenecarboxylate copolymer shows that the unsaturated polymer crosslinks by a chain reaction. At low doses, the kinetic chain length is about 4. Pendant norbornenyl groups accelerate crosslinking of a vinyl alcohol–vinyl acetate–vinyl chloride copolymer and convert poly(vinyl alcohols) and cellulose acetate from degrading to crosslinking polymers. A novel application of the Charlesby-Pinner plot strongly suggests linear dependence of the extent of crosslinking on the norbornenyl group concentration in a series of modified poly(vinyl alcohols). The greater effectiveness of pendant norbornenyl groups, compared to cyclohexenyl groups, demonstrates the importance of the reactivity of the double bond.     

Terpolymers. II. Mechanical properties and transition temperatures of terpolymers of vinyl stearate,vinyl acetate,and vinyl chloride

Vinyl stearate was studied as a major internal plasticizer in terpolymers containing vinyl acetate and vinyl chloride. The terpolymers were prepared by systematically replacing vinyl acetate by close increments of vinyl stearate starting with combinations of vinyl acetate and vinyl chloride, in increments, over all compositions. For comparison of properties, a complete range of copolymers of vinyl stearate and vinyl chloride, as well as mixtures of poly(vinyl chloride) and di-2-ethylhexyl phthalate (DOP) were also made. The external plasticizer was more efficient in reducing the glass temperature than was vinyl stearate. The decline in T_g with weight fraction of plasticizer was linear for the copolymers and terpolymers but concave downward with the liquid diluent. The linear decline was shown to involve mere additivity of the free volume contributed by each side-chain methylene (or methyl) group in both vinyl esters to reducing T_g. The mechanism of the diluent system was more complex. However, the magnitude of the reduction of tensile modulus at a given weight fraction of DOP could be equaled or exceeded by the same amount of vinyl stearate, by increasing the vinyl acetate content of the base copolymer to 40 mole-% or more. Unfortunately, the ultimate strengths and elongations of internally plasticized systems were reduced more than those of the mixtures at comparable compositions. Vinyl stearate was found to markedly retard photolytic degradation compared to both vinyl acetate and the external plasticizer in unstabilized samples having nearly the same thermal treatment. The effect was greater than could be ascribed to dilution by the long alkyl group. The production of a stearoyl radical more stable than the radicals initiating dehydrochlorination is suggested as a possible mechanism.     

Effect of a variable diffusivity on the migration of vinyl chloride from poly(vinyl chloride) pipe

Measurements of the extent of vinyl chloride migration from specimens of processed poly(vinyl chloride) (PVC) are used to calculate the diffusivity of vinyl chloride in PVC pipe compound. The migration is strongly affected by temperature and is slightly larger into water than into air. The equation for calculating vinyl chloride migration from PVC must be generalized to recognize a variable diffusivity to be useful for non-isothermal situations, as in the case of the measurements. The diffusivities calculated from the data with the generalized equation were confirmed by migration measurements from one in. pipe. Predictions with the calculated diffusivities and the generalized equation show that PVC pipe with a 3 mg/kg concentration of residual vinyl chloride will not release quantitatively detectable amounts of vinyl chloride (< .002 mg/kg) in a realistic time frame in potable water distribution.     

Vinyl chloride formation from the thermal degradation of poly(vinyl chloride)

The volatile products from the thermal degradation of poly(vinyl chloride) (PVC) resins and compounds are shown to contain trace amounts of vinyl chloride. Data presented show the effect of temperature and resin type on the amount of vinyl chloride formed. At the maximum temperatures involved in PVC processing which may reach 210°C., vinyl chloride monomer (VCM) evolution amounts to less than 1 ppm (resin basis). A technique employing a thermogravimetric balance and charcoal adsorption of volatiles is described for studying thermal degradation of PVC. The volatiles are analyzed for vinyl chloride by gas chromatography. Peak identity was confirmed by mass spectrometry.     

Study of dynamic mechanical properties of poly(vinyl chloride)–ethylene vinyl acetate copolymer and poly(vinyl chloride)–chlorinated ethylene vinyl acetate copolymer mixtures

The compatibility of the mixtures poly(vinyl chloride)—ethylene vinyl acetate copolymer and poly(vinyl chloride)—chlorinated ethylene vinyl acetate copolymer was studied by the method of dynamic mechanical testing. The character of G′ and G″ was confronted with the Takayanagi model. In all cases a limited compatibility of the components was observed.     

Miscibility and interaction studies on some aqueous polymer blend solutions by ultrasonic and rheological techniques

The aqueous solutions of poly(ethylene oxide)–polyacrylic acid, poly(vinyl pyrrolidone)–poly(vinyl alcohol), and poly(ethylene oxide)–poly(vinyl alcohol) blends have been studied by ultrasonic, rheological, and viscometric techniques. Extensive investigation over a wide range of concentrations, temperatures, compositions, pH, and shear rates indicate the degree of miscibility, extent of interaction between the polymers, and stoichiometry of the polymer complexes formed by the strong interaction between the polymers in solutions. These investigations indicate the miscibility of poly(ethylene oxide)–polyacrylic acid and poly(ethylene oxide)–poly(vinyl pyrrolidone) blends and the immiscibility of poly(ethylene oxide)–poly(vinyl alcohol) blends in conformity with other reported investigations. © 1994 John Wiley & Sons, Inc.