Vinyl polymerization initiated by peroxydiphosphate. VII. Polymerization of acrylonitrile initiated by peroxydiphosphate–ascorbic acid redox system

The polymerization of acrylonitrile was studied with a peroxydiphosphate–ascorbic acid redox system as the initiator. The rate of polymerization increased with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. It also increased with increasing monomer concentration and the monomer exponent was computed to be unity. The reaction was carried out at three different temperatures and the overall activation energy was computed to be 4.6 kcal/mol. The effect of certain surfactants on the rate of polymerization was investigated and a suitable kinetic scheme is described.     

Photopolymerization initiated by triphenylphosphine

The triphenylphosphine-initiated photopolymerization of acrylic monomers was studied. Only those monomers containing an α,β-unsaturated carbonyl group could be photoinitiated by triphenylphosphine, styrene being unaffected at the level of initiator employed. Kinetic studies with methyl methacrylate showed that the propagation was free radical in nature. Analysis of the resulting polymer indicated that it contained one phosphorus atom per chain. Ultraviolet spectral data suggested the formation of complexes between the triphenylphosphine and each monomer for which it is initiator. A relationship between the complex and the polymerization was shown to exist. A mechanism is proposed, involving a light-activated dipole interaction between the carbonyl oxygen and the phosphorus atom with the ultimate formation of a methacrylate type of free radical.     

Vinyl polymerization initiated by peroxydiphosphate. V. Polymerization of acrylonitrile initiated by peroxydiphosphate-cyclohexanol redox system in the presence of silver ion

The polymerization of acrylonitrile was carried out using peroxydiphosphate-cyclohexanol redox system in the presence of silver ion. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The plot of R_p vs [Ag⁺]^1/2 was linear, indicating 0.5 order with respect to [Ag⁺]. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 7.60 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been pictured.     

Anionic polymerization of lactones initiated by alkali graphitides. III. Polymerization of δ-valerolactone initiated by KC24

The anionic polymerization of δ-valerolactone initiated by KC₂₄ in xylene or tetrahydrofuran was investigated. The influence of the polymerization conditions on the amount and composition of the oligomers fraction and high polymers formed was tested. Experiments were done with a potassium mirror and benzophenone-potassium as initiators of the polymerization to check the influence of the layered structure of the initiator. It was found that the amount of the oligomers formed under comparable conditions increases in the order KC₂₄ (9%), potassium mirror (22%), benzophenone-potassium (56%). The highest yields of poly(δ-valerolactone) (over 90%) and highest intrinsic viscosities (1.0 dL/g and more) were achieved by the KC₂₄-initiated polymerizations in xylene.     

Anionic polymerization of lactones initiated by alkali graphitides. IV. Copolymerization of ε-caprolactone initiated by KC24

The copolymerization of ε-caprolactone (ε-CL) with octamethylcyclotetrasiloxane (D₄) and styrene (St) under the action of the second-stage potassium graphitide KC₂₄ was investigated. The copolymerizations were carried out in bulk or in xylene at 20°C. The content of the block copolymer ε-CL/D₄ in the polymerization mixture was 60–95%, the molecular weight ranging between 150,000 and 300,000. The data for the copolymers' composition obtained by ¹H-NMR and GPC showed 14–20% of D₄-units in the copolymer. The amount of the block copolymer ε-CL/St in the polymerization products was 0–87%, and the molecular weights in the case of copolymer formation were between 100,000 and 500,000. The content of St-units in the copolymers was from 10 to 75% as shown by GPC and ¹H-NMR. The mechanism of action of the initiator is discussed.     

Anionic polymerization of lactones initiated by alkali graphitides. I. Polymerization of ϵ-caprolactone initiated by KC24

The influence of the reaction conditions (time, temperature, concentrations of the monomer, and the initiator) on the amount and composition of the oligomers and high molecular products formed during the heterogeneous anionic polymerization of ?-caprolactone was investigated. The polymerization was initiated by KC₂₄ in xylene or tetrahydrofuran. Conditions were found under which intra- and intermolecular transesterification was strongly suppressed, thus providing the opportunity for the formation of polyesters with viscometric molecular masses of more than 300,000 and good yields (80% and higher). The total quantity of products with a viscometric molecular mass below 2500 did not exceed 15%; that of the cyclic dimer was not in excess of 5%. Peculiar features of the KC₂₄ initiated polymerization are the insignificant rise in the number of oligomers and the formation of high polymers even in strongly diluted solutions of ?-caprolactone (0.2 mol/L and lower). The quantity and molecular mass of the polymers obtained decreased as the temperature increased. It was also established that the polymerization of the cyclic dimer of ?-caprolactone is not initiated by KC₂₄.     

Nuclear processes initiated by electrons

Possible reasons for nuclear transformations upon powerful electric discharges in tubes containing deuterium-inert gases mixtures, along with the transmutation of various elements upon the laser excitation of metal nanoparticles or local explosions in liquid media are discussed. It is shown that the observed phenomena, particularly the fixation of neutrons and hard X-ray photons upon electrical discharges in mixtures with deuterium and the transformation of the stable ¹⁹⁶Hg isotope into ¹⁹⁷Au upon the laser excitation of Hg nanodrops in D₂O, along with the detected increase in the decay rate of ²³⁸U with violations of the secular fraction of ²³⁴Th after laser excitation of Au nanoparticles (～20 nm) in UO₂Cl₂ in D₂O and H₂O, could be related to the initiated interactions between electrons and nuclei.     

Vinyl polymerization initiated by peroxydiphosphate

Colloid and Polymer Science - The kinetics of aqueous polymerization of acrylamide and methacrylamide initiated by potassium peroxydiphosphate has been investigated. The kinetic orders with respect...     

Photopolymerizations initiated by oxime derivatives

A number of ester, urethane, and carbonate derivatives of biacetyl monooxime, dimethylglyoxime, and ketone oxime, were synthesized and their photolyses studied by means of ultraviolet spectroscopy. Most of the oxime derivatives photolyzed easily upon UV irradiation. Among them, however, only the free radicals formed by photolysis from the ester and carbonate of biacetyl monooxime could effectively initiate the polymerization of a vinyl monomer such as methyl methacrylate. Based on the results obtained from the monomeric reactions, syntheses of grafting polymers were made. Graft polymers were obtained by using a copolymer of methyl methacrylate and methacrylic acid–biacetyl monooxime ester (copolymer I) and that of methyl methacrylate and vinyl benzioc acid–biacetyl monooxime ester (copolymer II) in good yield and without the formation of homopolymer. It was also found that when copolymer I was employed as a grafting polymer, a considerable amount of main-chain scission was seen, but no chain degradation was noted in the case of copolymer II. Photocrosslinking was attempted by using these copolymers in the presence of divinyl benzene. It was confirmed that copolymer II was photocrosslinkable, whereas copolymer I underwent photodegradation.     

Vinyl polymerization. 416. Polymerization of vinyl monomer initiated by polyethyleneglycol

The polymerization of vinyl monomer initiated by polyethyleneglycol (PEG) in aqueous solution was carried out at 85°C with shaking. Acrylonitrile (AN), methyl methacrylate (MMA), and methacrylic acid were polymerized by PEG–300 (M?_n = 300), whereas styrene was not. The effects of the amounts of monomer and PEG, the molecular weight of PEG, and the hydrophobic group at the end of PEG molecule on the polymerization were studied. The selectivity of vinyl monomer and the effect of the hydrophobic group are discussed according to “the concept of hard and soft hydrophobic areas and monomers.” The kinetics of the polymerization was investigated. The overall activation energy in the polymerization of AN was estimated as 37.9 kJ mol^?1. The polymerization was effected by a radical mechanism.     

Vinyl polymerization initiated by peroxydiphosphate

The kinetics of the aqueous polymerization of acrylonitrile and methyl methacrylate initiated by the peroxydiphosphate-thioglycollic acid redox system was investigated at 40, 45, 50, 55, and 60 °C. The rates of polymerization were measured at different concentrations of oxidant, activator and monomer. From the results, it was concluded that the polymerization reaction is initiated by an organic free radical arising from the peroxydiphosphate-thioglycollic acid system and termination by mutual type. On the basis of experimental observations of the dependence of the rate of polymerization,R _p on various variables, a suitable kinetic scheme has been proposed.     

Kinetics of polymerization initiated by peroxides containing heterocyclic groups. I. Kinetics of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide

The rate and degree of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide and, for comparison, by dilauroyl and dibenzoyl peroxides were measured at several temperatures as a function of the initiator concentration. Also the rates of initiation were determined by the inhibition method with Banfield's radicals. The rate of polymerization initiated by difuroyl peroxide appears to be lower than could be expected from the rate of initiation determined by the inhibition method and from the decomposition of difuroyl peroxide. In the case of polymerization of vinyl acetate there are significant deviations from the proportionality between R_p and the square root of the initiator concentration, which follows from the conventional kinetic scheme. The degrees of polymerization are also low, and the plots of P _n^?1 versus R_p are not linear. These deviations can be accounted for by postulating a retardation effect of the furan cycle and chain transfer to difuroyl peroxide.     

Kinetics and mechanism of emulsion polymerization initiated by oil-soluble initiators. II. Kinetic behavior of styrene emulsion polymerization initiated by 2,2′-azoisobutyronitrile

In order to clarify the general kinetic behavior of emulsion polymerization initiated by oilsoluble initiators, the emulsion polymerization of styrene initiated by 2,2′-azoisobutyronitrile was as a typical example, investigated thoroughly. The variations of the polymerization rate and the number of polymer particles produced with changes in emulsifier (sodium lauryl sulfate), initiator, and monomer concentrations initially charged and the reaction temperature were determined. It is shown from these experimental results that the kinetic behavior of this emulsion polymerization system is quite similar to that of styrene emulsion polymerization initiated by the water-soluble initiator, potassium persulfate despite the difference in the principal loci of radical production in both systems.     

Photopolymerization initiated by carbonyl compounds. VII. Solvent effects on biacetyl photoinitiation

Biacetyl is solvated by methanol or water giving an α-substituted alkanone. Irradiation of the solvated species at 300 nm in the presence of vinyl acetate or vinyl pyrrolidone, produces a significant amount of polymer. The photoprocesses leading to active free radicals are considered to be a type I photocleavage of the α-substituted alkanone.     

Polymerization of cyclopentadiene initiated by methylaluminoxane

The polymerization of cyclopentadiene (CPD) was effectively initiated by methylaluminoxane (MAO) to generate poly(cyclopentadiene) (polyCPD). The effects on the polymerization of some reaction parameters such as the monomer concentration, the initiator concentration, and solvents were investigated. The conversion of CPD was monitored with gas chromatography to investigate the reaction kinetics. The polymerization rate was proportional to the concentrations of MAO in the first order and of the CPD monomer in the second order, and a reasonable cationic polymerization mechanism was suggested on the basis of the kinetic study. PolyCPD obtained at a low temperature could be dissolved in toluene or chloroform, and this indicated lower cross‐coupling during the polymerization reaction. ¹H NMR and IR analysis of the polymer indicated that there were almost equal amounts of 1,2‐enchainment and 1,4‐enchainment in the polymer chain. The measurement of polyCPD showed its unique properties as a potential candidate for stable wrappings or electronic packaging materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 264–272, 2006     

Tetrafluoroethylene telomerization initiated by benzoyl peroxide

The radical telomerization of tetrafluoroethylene initiated by benzoyl peroxide (BP) photolysis at λ ≥ 365 nm is studied in acetone, dichloromethane, carbon tetrachloride, and Freon 114B2 at 25°C. The products of synthesis are a mixture of telomers of different molar masses, segregated into soluble and insoluble fractions. To characterize the radicals initiating telomerization, crystalline BP and its solution in ethanol are subjected to low-temperature (77 K) photolysis, with the liquid system serving as a model for BP behavior in solutions of telogens. It is established that radicals are not only initiators but also participate in chain termination reactions, lowering the telomers’ molar mass and thus raising the proportion of the soluble fraction. Telomerization initiated by an initiator compound versus initiation by gamma radiation are compared and discussed.