Analysis and Characterization of Microwave Irradiation–Induced Graft Copolymerization of Methyl Methacrylate onto Delignified Grewia Optiva Fiber

Grafting of methyl methacrylate (MMA) onto delignified Grewia optiva fiber using ascorbic acid/H₂O₂ as an initiator was carried out under microwave irradiation. The effects of varying the microwave power, exposure time, and concentration of initiator and monomer of graft polymerization were studied to obtain maximum grafting percentage (26.54%). The experimental results showed that the optimal conditions for grafting were: exposure time, 10min; microwave power, 110 W; ascorbic acid concentration, 3.74mol/L × 10^?2; H₂O₂ concentration, 0.97mol/L × 10^?1; monomer concentration, 1.87mol/L × 10^?1. The graft copolymers were characterized by Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA).     

Grafting Vinyl Monomers onto Silk Fibers. XIII. Graft Copolymerization of Methyl Methacrylate onto Silk Using Fe3+−Cysteine Redox System

The graft copolymerization of methyl methacrylate onto silk fibers initiated by the ferric chloride-eysteine redox system has been investigated in aqueous medium. The rate of grafting was calculated by varying the concentrations of monomer, initiator, acidity of the medium, cysteine, and temperature. The percentage of grafting increases with an increase of Fe³⁺ concentration up to 2,5 × 10^?3 mol/L and thereafter it decreases. The graft yield increases steadily upon increasing the monomer concentration. The graft yield also increases with increasing cysteine concentration up to 0.5 × 10^?3 mol/L and then decreases. The effect of the perchloric acid concentration, temperature, solvents, and certain neutral salts on graft yield has also been investigated and a suitable reaction scheme has been proposed.     

Kinetics and mechanism of polymerization of acrylonitrile by peroxomonosulphate

The kinetics of polymerization of acrylonitrile initiated by peroxomonosulphate (PMS) has been carried out in the temperature range 45–60°C at constant ionic strength of 0.50 mol dm^?3 under deaerated conditions. The rate of polymerization R_p has been investigated at various concentrations of monomer and initiator. The effects of [monomer], [initiator], [H⁺], ionic strength, temperature, and reducing agents (organic and inorganic substrates) on the rate of polymerization have been observed. Activation energy was found to be 15.2 kcal mol^?1.     

Aqueous polymerization of acrylamide initiated by cerium (IV)–ethylenediamine tetraacetic acid redox system

Ethylenediamine tetraacetic acid (EDTA) terminated polyacrylamide was obtained by using the EDTA–cerium(IV) ammonium nitrate [Ce(IV)] redox initiator in the aqueous polymerization of acrylamide. The polymerization behaviors as a function of the concentration of Ce(IV), EDTA, and acrylamide as well as temperature were studied. The consumption rate of cerium(IV) depends a first-order reaction on the ceric ion concentration ([Ce(IV)]). The complex formation constant (K) and disproportionation constant (k_d) of Ce(IV)–EDTA chelated complex are 1.67 × 10⁴ and 3.77 × 10^?3, respectively. The rate dependences of polymerization on monomer concentration and EDTA concentration both follow a second-order reaction in the run of initial monomer concentration ([M]_i) equal to 0.2 mol dm^?3. The number average molecular weight increases linearly with the ratio of [M]_i/[Ce(IV)]_i. The mechanism and kinetics for the polymerization was proposed. The kinetic parameters involved were determined. © 1992 John Wiley & Sons, Inc.     

Use of samarium (III) acetate as initiator in ring-opening polymerization of trimethylene carbonate

Abstract

In this work was evaluated the activity of samarium acetate (III) (Sm(OAc)₃) as a possible initiator in the polymerization by ring opening of trimethylene carbonate (TMC). All polymerizations were carried out under solvent-free melt conditions in ampoules-like flasks, equipped with a magnetic stirrer. The effects of different parameters of reaction, such as molar ratio monomer to initiator, temperature and reaction time, on typical variables of polymers, e.g., conversion of TMC to poly(trimethylene carbonate) (PTMC), dispersity and molar mass, were analyzed. The molar ratio of monomer to initiator was varied between 0 and 1000?mol/mol and the temperature among 70 and 150?°C. Nuclear Magnetic Resonance (¹H-NMR and HMBC) and Size Exclusion Chromatography (SEC) were used to characterize the polymers. The results indicate that the Sm(OAc)₃ induces the polymerization of TMC to high conversion with number-average molecular weights of 3.11?×?10³ to 38.40?×?10³?Da. Based on the ¹H-NMR end-group analysis of low-molecular-weight PTMC, it was proposed a coordination–insertion mechanism for the polymerization, with a breakdown of the acyl-oxygen bond of the TMC. In according to the kinetic study carried out, the polymerization rate is first-order with respect to monomer concentration with apparent rate constants of k_ap?=?7.02?×?10^?4?mol?×?L^?1?×?h^?1.     

Kinetic and ESR studies on radical polymerization of methyl methacrylate in the presence of fullerene

The effect of fullerene (C₆₀) on the radical polymerization of methyl methacrylate (MMA) in benzene was studied kinetically and by means of ESR, where dimethyl 2,2′-azobis(isobutyrate) (MAIB) was used as initiator. The polymerization rate (R_p) and the molecular weight of resulting poly(MMA) decreased with increasing C₆₀ concentration ((0–2.11) × 10⁻⁴ mol/L). The molecular weight of polymer tended to increase with time at higher C₆₀ concentrations. R_p at 50°C in the presence of C₆₀ (7.0 × 10⁻⁵ mol/L) was expressed by R_p = k[MAIB]^0.5[MMA]^1.25. The overall activation energy of polymerization at 7.0 × 10⁻⁵ mol/L of C₆₀ concentration was calculated to be 23.2 kcal/mol. Persistent fullerene radicals were observed by ESR in the polymerization system. The concentration of fullerene radicals was found to increase linearly with time and then be saturated. The rate of fullerene radical formation increased with MAIB concentration. Thermal polymerization of styrene (St) in the presence of resulting poly(MMA) seemed to yield a starlike copolymer carrying poly(MMA) and poly(St) arms. The results (r₁ = 0.53, r₂ = 0.56) of copolymerization of MMA and St with MAIB at 60°C in the presence of C₆₀ (7.15 × 10⁻⁵ mol/L) were similar to those (r₁ = 0.46, r₂ = 0.52) in the absence of C₆₀. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2905–2912, 1998     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Potassium Bromate-Thiomalic Acid Redox System

The redox system composed of potassium bromate and thiomalic acid was used to initiate the aqueous polymerization of methyl methacrylate under nitrogen atmosphere at 35 ± 0.2°C. The initial rates of polymerization have been found to be approximately proportional to the first power of the initiator concentration in the range of 2.5 to 6.0 ± 10^?3 M and to the first power (1.15) of monomer concentration in the range of 3.72 to 11.16 ± 10^?2 M The overall rate was independent of activator concentration, approaching a maximum at 10 × 10^?3 M. The overall energy of activation was found to be 8.80 kcal/mol. The initial rate and the maximum conversion attained a maximum value at 35°C in the temperature range of 20 to 45°C.     

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.     

Aqueous polymerization of acrylamide initiated by acidic potassium permanganate–ascorbic acid redox system

The polymerization of acrylamide initiated by the acidic permanganate–ascorbic acid redox pair has been studied in aqueous media at 30 ± 0.2°C in nitrogen atmosphere. The initial rate of polymerization has been found to be proportional to nearly the first power of the catalyst KMnO₄ concentration within the range 6.0 × 10^?3–14.0 × 10^?3 mole/l. The rate is proportional to the first power of the monomer concentration within the range 4.00 × 10^?2–12.0 × 10^?2 mole/l. However, the rate of polymerization is independent of ascorbic acid concentration within the range 3.0 × 10^?3–6.0 × 10^?3 mole/l., but the further increase of the concentration depresses the rate of polymerization as well as maximum conversion. The initial rate increases but the maximum conversion decreases as the temperature is increased within the range 20–35°C. The overall energy of activation has been found to be 9.8 kcal/mole. The optimum amount of sulfuric acid is essential to initiate the polymerization but its presence in excess produces no effect either on the rate of reaction or the maximum conversion. Water-miscible organic solvents and salts, e.g., CH₃OH, C₂H₅OH, (CH₃)₂CHOH, KCl, and Na₂SO₄, depress the rate. Slight amounts of MnSO₄ · H₂O and a complexing agent NaF increase the rate of polymerization. Cationic and anionic detergents have been found to decrease and increase the rate, respectively, while nonionic surfactants have no effect on the rate of polymerization.     

Radical polymerization of vinyl thiocyanatoacetate: Participation of group‐transfer mechanism

Vinyl thiocyanatoacetate (VTCA) was synthesized, and its radical polymerization behavior was studied in acetone with dimethyl 2,2′‐azobisisobutyrate (MAIB) as an initiator. The initial polymerization rate (R_p) at 60 °C was expressed by R_p = k[MAIB]^0.6±0.1 [VTCA]^1.0±0.1 where k is a rate constant. The overall activation energy of the polymerization was 112 kJ/mol. The number‐average molecular weights of the resulting poly (VTCA)s (1.4–1.6 × 10⁴) were almost independent of the concentrations of the initiator and monomer, indicating chain transfer to the monomer. The chain‐transfer constant to the monomer was estimated to be 9.6 × 10^?3 at 60 °C. According to the ¹H and ¹³C NMR spectra of poly (VTCA), the radical polymerization of VTCA proceeded through normal vinyl addition and intramolecular transfer of the cyano group. The cyano group transfer became progressively more important with decreasing monomer concentration. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 573–582, 2002; DOI 10.1002/pola.10137     

Kinetics of the Copolymerization of Methyl Vinyl Ketone and Acrylamide Initiated by the Adduct of Methyl Vinyl Ketone and Imidazole

N-(Butyl-3-one)imidazole acts as an initiating adduct which is formed in the anionic polymerization of methyl vinyl ketone (MVK) induced by imidazole (Im) and is directly formed from Im and the MVK monomer. The kinetics of the anionic homopolymerization of MVK and acrylamide (AAm) under argon in the presence of the adduct were investigated in tetrahydrofuran (THF). The rate of polymerization for the MVK system is expressed as R_p = k[Adduct] [MVK], where k = 3.1 × 10^?6 L/(mol·s)in THF at 30°C. The overall activation energy, E_a , was found to be 5.34 kcal/mol. The R_p for the AAm system is expressed as R_p = k[Adduct] [AAm], where k = 6.8 × 10^?6 L/(mol·s) in THF at 30°C, with E_a 7.78 kcal/mol. The mechanism of the polymerization induced by the initiator adduct is discussed on the basis of these results.     

Photopolymerization initiated by charge transfer complex. II. Photopolymerization of methyl methacrylate with the use of γ-picoline–bromine charge transfer complex as photoinitiator

Polymerization of MMA was carried out in the presence of visible light (440 nm) with the use of γ-picoline-bromine charge transfer complex as the initiator. The rate of polymerization R_p increases with increasing monomer concentration and the monomer exponent was computed to be unity. The rate of polymerization increases with increasing initiator concentration. The initiator exponent was computed to be 0.5. The reaction was carried out at three different temperatures and the overall activation energy was calculated to be 4.5 kcal/mol. The polymerization was inhibited in the presence of hydroquinone. Kinetic and other evidence indicates that the overall polymerization takes place by a radical mechanism.     

Effect of triphenyl phosphite on the radical polymerization of styrene and methyl methacrylate

The effects of triphenyl phosphite (TPP) on the radical polymerization of styrene (St) and methyl methacrylate (MMA) initiated with α,α,-azobisisobutyronitrile (AIBN) was investigated at 50°C. The rate of polymerization of St and MMA at a constant concentration of TPP was found to be proportional to the monomer concentration and the square root of the initiator concentration. The rate of polymerization and the degree of polymerization of both St and MMA increased with increasing TPP concentration. The accelerating effect was shown to be due to the decrease of the termination rate constant k_t with an increase in the viscosity of the polymerization systems. The chain transfer constant C_tr of TPP in St and MMA systems was determined from the degree of polymerization system. The C_tr of TPP was almost zero in the St system and 6.5 × 10^?5 in the MMA system.     

Kinetics of polymerization of N-tert-butylacrylamide. Part II

The effect of ferric chloride on the kinetics of the radical polymerization of N-tert-butylacrylamide has been investigated in methanol solution at 25°C, with the use of 4,4′-dicyano-4,4′-azodipentanoic acid as initiator. A shrinkage factor of 0.193 mmole polymerized for 1 mm contraction in a capillary of 1 mm diameter has been obtained from density measurements. In the absence of ferric chloride, rates of polymerization were found to be proportional to the concentration of monomer and to the square root of the initiator concentration. With ferric chloride present, the rate of polymerization becomes directly proportional to the initiator concentration and inversely proportional to the concentration of ferric salt. From measurements of the rates of production of ferrous iron, the specific rate constant of the initiation reaction has been found to be (1.8 ± 0.4) × 10^?6sec^?1 at 25°C, compared with a value of 7.63 × 10^?8 sec^?1 calculated from the kinetic data obtained with no ferric salt present. The value of the ratio k_p/k₄. where k_p is the propagation coefficient and k₄ is the velocity coefficient for termination by ferric chloride, has been calculated to be 6.0 × 10^?4 at 25°C, which is considerably smaller than the value found for the ferric chloride-terminated polymerization of acrylamide in water. This markedly lower value of k_p/k₄ has been attributed principally to the steric effect of the tert-butyl group on the magnitude of k_p.     

Aqueous polymerization of acrylamide

The polymerization of acrylamide (I) initiated by a potassium bromate—thioglycollic acid (TGA) redox pair has been studied in aqueous media at 30°C in a nitrogen atmosphere. The reaction order related to the catalyst concentration (KBrO₃) was 0.501, which indicated a bimolecular mechanism for the termination reaction in the range of 1.0?3.0 × 10^?3 mole/liter. The polymerization rate varied linearly with monomer (I) concentration over the range of 1.0?5.0 × 10^?2 mole/liter. A typical behavior is observed, however, by changing the thioglycollic acid concentration. The initial rate of polymerization (Ri), as well as the maximum conversion, increases by increasing the temperature to 30°C, but the initial rate and the maximum conversion falls as the temperature rises above 30°C. The overall energy of activation is 6.218 kcal in the temperature range of 20–40°C. Water-miscible organic solvents, namely, CH₃OH and C₂H₅OH, depress the rate of polymerization.     

Aqueous polymerization of acrylonitrile by ascorbic acid–peroxodisulfate redox system

The polymerization of acrylonitrile initiated by an ascorbic acid–peroxodisulfate redox system was studied in an aqueous solution at 35°C in the presence of air. Molecular oxygen was found to have no effect on the polymerization reaction. An increase in ionic strength slightly increased the rate. The overall rate of polymerization, R_p, showed a square dependence on [monomer] and a half-order dependence on [peroxodisulfate]. A first-order dependence on [ascorbic acid] at low concentrations (<3.0 × 10^?3 mol L^?1) followed by a decrease in R_p at higher concentrations of ascorbic acid (>3.0 × 10^?3 mol L^?1) was also noted. R_p remained unchanged up to 40°C and showed a decline thereafter. Addition of catalytic amounts of cupric ions decreased the rate whereas ferric ions were found to increase the rate. Added sulfuric acid in the range (6.0?50.0) × 10^?5 mol L^?1 decreased the R_p.     

Cerium (IV)-2-chloroethanol redox-pair initiated polymerization of acrylamide in aqueous medium

The kinetics of acrylamide polymerization has been investigated by employing cericammoniumnitrate-2-chloroethanol redox pair under nitrogen atmosphere at 30 ± 1°C. The rate of monomer disappearance is directly proportional to the concentration of 2-chloroethanol (1.0 × 10^?2 ? 10.0 × 10^?2 mol. dm^?3) and is inversely proportional to the ceric ion concentration (2.5 × 10^?3 ? 10.0 × 10^?3 mol. dm^?3) but shows square dependence to the concentration of monomer (5.0 × 10^?2 ? 25.0 × 10^?2 mol. dm^?3). The rate of ceric ion disappearance is directly proportional to the initial concentration of ceric ion and 2-chloroethanol but independent of acrylamide concentration. The viscometric average molecular weight (M _v) decreases on increasing the concentration of ceric ion and increases on increasing the concentrations of acrylamide and 2-chloroethanol. A tentative mechanism has been proposed.     

Studies on the kinetics of ceric–thiourea-initiated aqueous polymerization of methyl methacrylate. I. Mechanistic features in moderately acid solution

The kinetics of the aqueous polymerization of methyl methacrylate by a ceric-thiourea initiator system in moderately acid solution (pH 2.15) was studied. The rate of polymerization was proportional to 0.41 power of ceric concentration, 0.32 power of thiourea concentration, and 1.18 power of monomer concentration. The degree of polymerization was smaller than expected from the rate of polymerization. Initiation efficiency was less than one. There was no evidence of any ceric ion termination in the concentration range of 2.50 × 10^?4–2.00 × 10^?3M studied. The results are explained in terms of partial primary radical termination; the principal mode of termination, however, was bimolecular.     

Photopolymerization initiated by charge-transfer complex. I. Photopolymerization of methylmethacrylate with the use of quinaldine-bromine and lutidine–bromine charge-transfer complexes as photoinitiator

Photopolymerization of MMA was carried out with quinaldine–bromine (QN–Br₂) and lutidine–bromine (LU–Br₂) charge-transfer complexes as initiators. The rate of polymerization R_p increased with rising monomer concentration and the monomer exponent was computed as unity. At first the rate of polymerization accelerated and then reduced as the initiator concentration was increased. The initiator exponent was 0.5. The reaction was carried out at three different temperatures and overall activation energy was calculated at 4.0 kcal/mol. The kinetic data and other evidence indicate that the overall polymerization takes place in a radical mechanism. A suitable mechanism is suggested.     

Polymerization initiated by ylide: Polymerization of ethyl methacrylate with the use of 4-picolinium p-chloro phenacylide as initiator

The ylide 4-picolinium, p-chloro phenacylide-initiated thermal polymerization of ethyl methacrylate (EMA) was studied. 4-Picolinium p-chloro phenacylide induces the thermal polymerization of ethyl methacrylate at 65°C. The rate of polymerization (R_p) rose as the initiator concentration increased from 2 × 10^?3 to 4 × 10^?3 M and the initiating exponent was computed as 1.9. The R_p decreased as the concentration of ylide increased from 6 × 10^?2 to 1M. The greater initiator concentration also affected the molecular weight inversely. The polymerization was carried out at different temperatures and the overall activation energy was computed as 4.08 Kcal/mol. Polymerization was inhibited in the presence of hydroquinone as a radical scavenger. Kinetic studies and other data show that the overall polymerization takes place in a radical mechanism. The various kinetic parameters, such as the rate and average degree of polymerization, molecular weight, and energy of activation of the present system, were evaluated.