Radiation-induced polymerization of water-saturated styrene in a wide range of dose rate

Radiation-induced polymerization of water-saturated styrene (water content 3.5 × 10^-2 mole/liter) was carried out in a wide range of dose rate between 1.2 × 10³ and 1.8 × 10⁷ rad/sec, and compared with the polymerization of the moderately dried styrene (water content 3.2 × 10^-3 mole/liter). Molecular weight distribution curves of the polymerization products showed that they were generally consisted of four parts, namely, oligomers, radical, cationic, and super polymers. Contributions of the four constitutents to the polymerization and the number average degrees of polymerization (DP) of the four kinds of polymers were calculated by the graphical analysis of the curves. The rate of radical polymerization and DP of radical polymers are independent of the water content; the dose rate dependences of the polymerization rate and DP agree with the well known square root and inverse square root laws, respectively, of the radical polymerization of styrene. The rate of ionic polymerization is directly proportional to the dose rate, but it decreases, at a given dose rate, inversely proportional to the water content of styrene. DP of ionic polymer is independent of the dose rate but decreases with increasing water content. The super polymer of DP about 10⁴ is not formed in the case of the moderately dried styrene. G values for the initiating radical and ion formation are calculated to be, independently of the dose rate and water content, 0.66 and 0.027, respectively. It was suggested that oligomer was formed in the early stage by the interaction of cation with anion and only those cations which had survived underwent polymerization.     

Determination of Rate Constants for Ozonation of Ofloxacin in Aqueous Solution

The ozonation of the quinolone antibiotic ofloxacin in water has been investigated with focus on kinetic parameters determination. The apparent stoichiometric factor and the second-order rate constants of the reactions of ozone and hydroxyl radical with ofloxacin were determined at 20 °C in the pH range of 4–9. The apparent stoichiometric factor was found to be about 2.5 mol O₃/mol ofloxacin regardless of the pH. The rate constant of the reaction between ozone and ofloxacin was determined by a competitive method (pH = 6–9) and a direct ozonation method (pH = 4). It was found that this rate constant increases with pH due to the dissociation of ofloxacin in water. The direct rate constants of ofloxacin species were determined to be 1.0?×?10², 4.3?×?10⁴ and 3.7?×?10⁷ for cationic, neutral-zwitterion and anionic species, respectively. Accordingly, the attack of ozone to ofloxacin mainly takes place at the tertiary amine group of the piperazine ring, though some reactivity is also due to the quinolone structure and oxazine substituent. The rate constant of the reaction between ofloxacin and hydroxyl radical was obtained from UV/H₂O₂ photodegradation experiments. It was found that this rate constant varies with pH from 3.2?×?10⁹ at pH 4 to 5.1?×?10⁹ at pH 9.     

Radiation-induced seeded copolymerization of tetrafluoroethylene with propylene. II. Kinetic analysis

The radiation-induced seeded copolymerization of tetrafluoroethylene with propylene was kinetically analyzed by assuming that growing radical in polymer particle is deactivated by degradative chain transfer to propylene and/or by recombination with newly entered radical which grows for a while before recombination. Apparent rate constant of initiation is 2.6 × 10^?9 mole/liter rad independent of the monomer composition in polymer particles. Apparent rate constant of propagation lies in the range of 10⁵ hr^?1 increasing with tetrafluoroethylene fraction. Change in apparent rate constant of chain transfer with propylene fraction suggests that first-order termination by radical occlusion or radical escape to aqueous phase may occur simultaneously with the degradative chain transfer. Average number of radical in a particle is found to increase with dose rate and levelled off at the value of 0.9. The higher value above 0.5 is explained by Trommsdorff effect. The dose rate exponent of average number of radical changes from 1 to 0 with increasing dose rate. This change is consistent with the dose rate effect on the polymerization rate under the constant number of polymer particles.     

Mechanistic and kinetic studies on the polymerization of styrene initiated by dimethyl sulfonium 2-pyridyl carbonyl methylide

Dimethyl sulfonium 2-pyridyl carbonyl methylide (Y_py-s) initiated radical polymerization of styrene in dimethyl sulfoxide at 85±0.1°C for 6 h under a nitrogen blanket using dilatometric techniques has been studied. The initiator and monomer exponent values were calculated to be 0.5 and 1.2, respectively. The system follows ideal radical kinetics with bimolecular termination. The higher monomer exponent value is ascribed to significant solvent effects on the initiation rate. The overall activation energy and average value of k²_p/k_t are 52.0 kJ mol^?1 and 1.0 × 10^?3 litre mol^?1 s^?1, respectively. The polymerization was retarded in the presence of hydroquinone or benzene; dimethylformamide, however, enhanced the rate of polymerization. Kinetic data and ESR studies indicate that the overall polymerization takes place via triplet carbene formation which acts as a source of free radicals.     

Studies on suspension and emulsion. XLVI. Emulsifier-free emulsion polymerization of styrene in acetone–water

Emulsifier-free emulsion polymerization of styrene in acetone–water medium was carried out using potassium persulfate as initiator. Below acetone content of 40 vol %, stable emulsion was prepared and polymerizations were remarkably fast compared with those in pure water. The particle size decreased from 0.5 to 0.17 μm with an increase in acetone content in the range 0–40 vol %, and the distributions were very sharp. The optimum polymerization for the preparation of the stable emulsion was: styrene, 20 vol %; acetone/water, 40/60 (v/v); KPS, 3.4 × 10^?3 mole/l; temp., 90°C.     

The synthesis of (N1E,N4E)-N1,N4-bis(pyridine-2-YL) ethylene benzene-1,4-diamine and investigation of its efficiency as new binuclear catalyst complex in copper-based ATRP

(N¹E,N⁴E)-N¹,N⁴-bis(pyridin-2-yl) ethylene benzene-1,4-diamine (BPEBD) was synthesized by condensation of 2-acetyl pyridine and 1,4-diaminobenzene and its efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) and styrene (S) was investigated. Linear first-order kinetic plots were obtained. However, there were induction periods. The apparent rate constant values of ATRP of MMA with CuCl/BPEBD catalyst system in toluene were found to be between 2.10 × 10^?5 and 9.83 × 10^?5 s^?1, while they were between 6.67 × 10^?6 and 3.30 × 10^?5 s^?1 in the case of acetonitrile, indicating the presence of a low radical concentration throughout the polymerizations. Low apparent rate constant values denote a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of 1. In the ATRP of MMA in toluene, M _n,GPC values increased linearly with conversion and these molecular weight values were close to M _n,th in comparison to that of in acetonitrile. In the polymerization of S, the control of molecular weights was not good, although the reactions were first-order kinetics. Cyclic voltammetry measurements confirmed that CuCl/BPEBD complex in acetonitrile gives quasi-reversible redox couples, and copper (I) centers in CuCl/BPEBD binuclear catalyst complexes are readily oxidized and it potentially suits to facile ATRP.     

Miniemulsion copolymerizations of styrene and methyl methacrylate in the presence of reactive costabilizer

Miniemulsion stability of three‐component disperse phase systems comprising styrene [ST (1)], methyl methacrylate [MMA (2)], and stearyl methacrylate [SMA (3)] was investigated. The Ostwald ripening rate (ω) increases with increasing MMA content in the monomer mixture. The empirical equation 1 /ω = k(φ₁/ω₁ + φ₂/ω₂) + φ₃/ω₃ was proposed to adequately predict the miniemulsion stability data. The empirical parameter k was determined to be 555.77, and the Ostwald ripening rate (ω₃) and water solubility of SMA were estimated to be 8.77 × 10^?21 cm³/s and 1.90 × 10^?9 mL/mL, respectively. A water‐insoluble dye was used as a molecular probe to study particle nucleation mechanisms in the miniemulsion copolymerizations. In addition to the primary monomer droplet nucleation, homogeneous nucleation also plays an important role in the formation of particle nuclei, and this mechanism becomes more important for the polymerization systems with higher MMA contents as a result of the enhanced aqueous phase polymer reactions. The polymer composition data suggest that, during the early stage of polymerization, MMA is consumed more rapidly by free radical polymerization compared with ST. The final latex particle surface potential data also support this conclusion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sodium bisulfite-initiated polymerization of methyl methacrylate in aqueous medium in the presence of the metal oxides CuO and MnO2

Sodium bisulfite-initiated polymerization of methyl methacrylate (MMA) in water medium was carried out in the absence and in the presence of cupric oxide and manganese dioxide using various initiator concentrations at various temperatures ranging from 30° to 60°C. It seems that the metal oxide–water interface plays an important role, as it has been found that both oxides accelerate the rate of polymerization. Cupric oxide was found to be more effective than manganese dioxide. The cupric oxide was found to have nearly the same catalytic effect as the cuprous oxide, and manganese dioxide was found to be somewhat more effective than titanium dioxide. The initial rate of polymerization increased from 2.3 × 10^?5 mole/(l.sec) to 3.4 × 10^?4 mole/(l.sec) and to 6.6 × 10^?5 mole/(l.sec) when the metal oxide concentration increased from 0 to 3 g/l. in case of cupric oxide and manganese dioxide, respectively. The initial rate of polymerization increased from 3.7 × 10^?4 mole/(l.sec) to 4.2 × 10^?4 mole/(l.sec) and from 7.2 × 10^?5 to 2.2 × 10^?4 mole/(l.sec) when the temperature was raised from 30° to 60°C in the presence of cupric oxide and manganese dioxide, (9 g/l.), respectively. Both the rate of polymerization and the number-average molecular weights were found to increase with increase the monomer concentration; the rate values were higher while the number-average molecular weights were lower in case of cupric oxide than in case of manganese dioxide. For example, the rate of polymerization increased from 2 × 10^?5 mole/(l.sec) to 8.1 × 10^?5 mole/(l.sec) and from 1.9 × 10^?5 mole/(l.sec) to 6.9 × 10^?5 mole/(l.sec); and the number-average molecular weight increased from 0.7 × 10⁵ to 2.2 × 10⁵ and from 1.5 × 10⁵ to 4.9 × 10⁵ in the presence of cupric oxide and manganese dioxide (10 g/l.), respectively, when the monomer concentration was increased from 23.5 g to 94 g/1. water. The apparent energy of activation for the polymerization of methyl methacrylate in water medium between 40° and 50°C was found to be 0.8 and 4.3 kcal/mole when using cupric oxide and manganese dioxide (9 g/l.), respectively.     

Radiation-induced graft copolymerization of styrene to cellulose

The radiation-induced graft copolymerization of styrene to cellulose has been studied in vacuo at 30°C and at dose rates from (0.37 to 8.73) × 10^?2 W/kg. Dioxan was used as solvent for monomer and polystyrene homopolymer, and water (2% total volume) was incorporated as swelling agent for cellulose. The concentration of styrene in the bulk medium was varied from 0.432 to 3.46 moles/l., and the rates of both grafting and homopolymerization were shown to be proportional to [monomer] · [intensity]^1/2. The value of 3.3 × 10^?4 l. mole^?1 sec^?1 derived for k_p²/k_t in homopolymerization is similar to that for normal free-radical polymerization of styrene. However, reduced termination during grafting yielded a much higher value (58 l. moles^?1 sec^?1). Degradation of cellulose in the absence of monomer was followed viscometrically, and values of 13.5 and 24.6 were derived for G (scission) in vacuo and in air, respectively.     

Copolymerization of styrene and methyl methacrylate mediated by iron wire/N,N,N′,N′-tetramethyl-1,2-ethanediamine as catalyst in the presence of air

Random copolymers of P(MMA-co-styrene) were synthesized via single electron transfer-living radical polymerization (SET LRP) at 25 °C in N,N-dimethylformamide (DMF) and benzene using CCl₄ as initiator and Fe(0) wire/N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA)/hydrazine (NH₂NH₂) complexes as catalyst in the presence of air. Fe(0) wire-mediated single electron transfer-living radical copolymerization of MMA and styrene represented a robust and versatile technique to synthesize the well-defined copolymers. The copolymerization rate was faster in DMF than in benzene, as determined by the apparent rate constants. The results showed that the copolymerization followed first-order kinetics model in the presence of polar DMF and non-polar benzene. The molecular weights increased linearly with the increase of monomer conversion with a narrow polydispersity index when the conversion was beyond 25 %. The polarity and the quantity of solvent had significant effects on the polymerization, and the apparent rate constants were 1.28 × 10^?4, 1.21 × 10^?4, and 9.23 × 10^?5 s^?1 in the order of DMF amount, 5, 10, and 15 mL. The conversion increased from 29.3 to 48.5 % and the polydispersity index (PDI) changed from 1.24 to 1.21 with [CCl₄]₀/[TMEDA]₀ molar ratio changing from 1:0.5 to 1:5. The chain extension experiment demonstrated that the copolymerization exhibited a living characteristic.     

Graft polymerization of some vinyl monomers onto acrylic rubber. I. Chain transfer and grafting reaction

The grafting reactions of styrene (St), methyl methacrylate (MMA), and vinyl acetate (VAc) were investigated in the presence of n-butyl acrylate–acrylonitrile copolymer. Results showed that the nature of monomer and initiator were the major factors influencing the grafting activity. The grafting efficiency was 0.87 for St, 0.26 for MMA, and 0.18 for VAc under the most favorable conditions. Acrylic rubber reduced the rate of polymerization, and the retarding effect increased in the order St, MMA, VAc. The chain transfer constants for acrylic rubber were evaluated to be 4.8 × 10^?4 for St, 1.27 × 10^?3 for MMA, and 1.45 × 10^?3 for VAc. The rate of polymerization and the grafting efficiency decreased with increasing acrylonitrile content in acrylic rubber, while the chain transfer constant of St for acrylic rubber remained practically unchanged.     

Laser flash photolysis investigations on primary processes of the sensitized polymerization of vinyl monomers: 1. Experiments with benzophenone

The laser flash photolysis technique was used in order to evaluate kinetic parameters concerning the efficiency of benzophenone (BP) as a photosensitizer for polymerizations. Rate constants (in M^?1 sec^?1) of the reaction of triplet BP with monomers were measured (e.g. styrene, 3.3 × 10⁹; methyl methacrylate, 6.9 × 10⁷; acrylonitrile, 3.4 × 10⁷; vinyl acetate, 5.4 × 10⁶). The rate constant of the reaction of triplet BP with tetrahydrofuran is 3 × 10⁶M^?1sec^?1. From these results it can be derived, for example, that the BP photosensitized polymerization of styrene is not feasible. Ketyl radicals of BP were found to react relatively slowly with vinyl acetate (5.5 × 10³M^?1sec^?1), acrylonitrile (3.8 × 10³M^?1sec^?1) and methyl methacrylate (9.0 × 10³M^?1sec^?1). Based on these data it was estimated that benzpinacol should not be formed as a major reaction product at relatively low incident light intensities and at monomer concentrations greater than 1 mol/l.     

Kinetics and modeling of diethylene glycol bisallyl carbonate bulk polymerization

The free‐radical polymerization kinetics of diethylene glycol bisallyl carbonate in bulk were investigated with Fourier transform infrared and Fourier transform Raman techniques in a wide temperature range of 50–140°C with four different peroxide initiators. In addition, the ratios of the degradative kinetic rate constant to the propagation rate constant under different reaction conditions were obtained from molecular weight measurements under various reaction conditions. The ratio of the chemically controlled termination and propagation rate constants of the polymerization system were obtained with the initial rates of polymerization and the number‐average molecular weight data, which were between 8.22 × 10^?5 and 1.47 × 10^?3 L mol^?1 s^?1. The initiator efficiencies were evaluated with special experiments at low initiator concentrations with the theory of dead‐end polymerization. The computed conversions from the developed kinetic model were in good agreement with the conversion and molecular weight measured data. The values of the diffusion‐controlled propagation and termination rate constants, with clear and physical meaning, were the only two parameters obtained from the developed kinetic model fitting the measured conversion points. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 345–357, 2005     

Anionic polymerization of styrene in triglyme-benzene mixtures

Living anionic polymerization of styrene was kinetically investigated in triglyme-benzene mixtures. At low concentrations of triglyme the overall propagation rate constant, k_p, was much larger than at the same concentration of monoglyme (DME) in DME-benzene mixtures. The Szwarc-Schulz plot did not have negative slopes for lithium and sodium salts at triglyme contents of 5～20vol%, and no contribution of free anions to the propagation was observed for the sodium salt. The sodium ion pair was more highly reactive than the lithium ion pair; thus at 25°C, the ion pair rate constant, k′_p, for the lithium salt was 43, 102, 135 and 165 M^?1sec^?1 at triglyme concentrations of 5, 10, 15, and 20%, respectively, while that for the sodium salt was 410, 920, and 1460 M^?1sec^?1 in 5, 10, and 15% triglyme, respectively. The dissociation constant, K, for the lithium salt was 2·4×10^?11, 1·9×10^?10 and 1·3×10^?9 M in 10, 15, and 20% triglyme, respectively and the free ion rate constant, k″_p, was 2～2·5×10⁴ M^?1sec^?1 for the lithium salt.     

Aqueous dispersion polymerization of acrylamide with quaternary ammonium cationic comonomer

Using aqueous solution of ammonium sulfate as medium, acrylamide (AM) and dimethylaminoethyl methacrylate methyl chloride (DMC) as main raw materials, poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and 2,2′‐azobis (2‐amidinopropane) dihydrochloride (V‐50) as initiator, the cationic polyelectrolyte of P(DMC‐AM) was synthesized by aqueous dispersion polymerization. The effects of the major reaction variables on synthesis conditions, product characteristics (particle size and molecular weight), and polymerization rate were investigated. The polymerization was retarded by the presence of the ammonium sulfate. The optimum reaction conditions for obtaining a stable aqueous dispersion were concentrations of 1.8 × 10^?4–7.0 × 10^?4 mol L^?1 for V‐50, 1.5–3.5% for stabilizer, and 23.2–30.0% for salt. The molecular weight of PDMC formed was 1.5 × 10⁵ to 7.0 × 10⁵. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Zinc ion-imprinted polymer based on silica particles modified carbon paste electrodes for highly selective electrochemical determination of zinc ions

ABSTRACT

In this study, Zn(II) ion-imprinted polymer was prepared on the surface of vinyl silica particles and applied for detection of Zn(II) ions using differential pulse voltametry. The ion- imprinted polymer particles were prepared by free radical polymerization. The prepared particles were characterized by different morphological and elemental techniques. The ion-imprinted particles were used to fabricate the carbon paste electrode as a zinc ions sensor. The modified zinc sensor showed linear response in the concentration range 6.12 × 10^?9 to 4.59 × 10^?8 mol L^?1. The limit of detection and limit of quantification of the electrode were 1.351 × 10^?8 and 4.094 × 10^?8 mol L^?1, respectively.     

Macromonomers by activated polymerization of oxiranes. Synthesis and polymerization

Macromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by the activated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DP _n ～ 15 for propylene oxide and DP _n ～ 20 for epichlorohydrin, polymerization proceeds as a living process, giving with quantitative yields macromonomers with functionality equal to one, controlled molecular weight and narrow molecular weight distribution (M _wM _n<1.2) free of side products. In the higer molecular weight region, side reactions become increasingly noticeable. Propylene oxide macromonomers undergo radical homopolymerization. Homopolymerization of macromonomer with M _n = 8×10² gives graft copolymers with M _n up to 7.2×10³ in copolymerization with styrene, completely soluble graft copolymers with M _n ～ 2×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M _n ～ 6×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M_n～ 6×10⁴, which are converted in the later stages into insoluble gels, apparently due to the chain transfer to chloromethly groups of the polyepichlorohydrin chains.     

RAFT with Bulk and Solution Polymerization: An Approach to Mathematical Modelling and Validation

Reversible addition fragmentation chain transfer (RAFT)-mediated polymerization is a novel technique used to impart a living character in free radical polymerization. A mathematical model accounting for the concentrations of the propagating, intermediate, dormant and dead chains is developed based on their reaction pathways. The kinetic scheme used includes initiation, propagation, pre-equilibrium, core-equilibrium and termination of the propagating radicals along with termination reactions of the carbon-centered intermediate radical. This model is combined with chain-length dependant termination model in order to account for the decreased termination rate. The model has been validated against experimental data for solution polymerization of styrene with dithiobenzoate at 80°C. The fragmentation rate coefficient was used as a model parameter and a value equal to 6×10⁴ sec^?1 was found to provide a good agreement with the experimental data. The model predictions indicate that the observed retardation can be attributed to the cross termination of the intermediate radical and, to some extent, to the RAFT effect on increasing the average termination rate coefficient. The hypothesised irreversible self termination was found to have a negligible effect on the polymerization rate. While the linear growth of the number average molecular weight along with the low polydispersity, reveal the living nature of RAFT agent and the importance of the transfer constant in controlling these properties.     

New aspects of viscosity effects on the photopolymerization kinetics of the 2,2‐bis[4‐(2‐hydroxymethacryloxypropoxy)phenyl]propane/triethylene glycol dimethacrylate monomer system

The photopolymerization kinetics and viscosity behavior of 11 2,2‐bis[4‐(2‐hydroxymethacryloxypropoxy)phenyl]propane/triethylene glycol dimethacrylate mixtures were investigated. The viscosity was studied at six temperatures (20–70°C), and the activation energies for the viscosity were determined. The excess logarithm viscosities were calculated and found to be negative over the whole composition and temperature ranges; they were fitted to the Redlish–Kister polynomial equation. The kinetic analysis of the photopolymerization was carried out at three polymerization temperatures (20, 40, and 60°C). The results proved the existence of the most reactive composition (reaching the highest value of the maximum polymerization rate), but the ratio of the monomers in this composition, close to equimolar, showed a tendency to change with the polymerization temperature. The viscosities of the most reactive compositions lay in the range of about 0.1–1.2 Pa s, which was narrow in comparison with the range of viscosities of all the compositions used in the kinetic studies (from 3 × 10^?3 to 1.5 × 10³ Pa s). The activation energies for the polymerization rates were calculated and correlated with the viscosity changes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008