Rate Of Monomer Disappearance Research Articles

Polymerization of methyl acrylate in the presence of ultrasound and peroxodisulfate

A systematic polymerization kinetic study of methyl acrylate with an added initiator, peroxodisulfate, in the presence of low-power ultrasound was done. The polymerization experiments were conducted at various concentrations of monomer and initiator at different temperatures (303–323 K). The polymerization was found to proceed without an induction period, and the steady state was attained in a fairly short time. The rate of monomer disappearance showed a second-order dependence on monomer concentration. The chain lengths of the polymer were calculated, and we found that the chain length increased with increasing monomer concentration and decreased with increasing initiator concentration. The reaction scheme proposed is based on the kinetic studies that indicated linear termination by sulfate-ion-radical-incorporating direct reaction between the monomer and the initiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Investigations of thermal polymerization in the stable free-radical polymerization of 2-vinylnaphthalene

The feasibility of utilizing stable free-radical polymerization (SFRP) in the synthesis of well-defined poly(2-vinylnaphthalene) homopolymers has been investigated. Efforts to control molecular weight by manipulating initiator concentration while maintaining a 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO):benzoyl peroxide (BPO) molar ratio of 1.2:1 proved unsuccessful. In addition, systematic variations of the TEMPO: BPO molar ratio did not result in narrow molecular weight distributions. In situ Fourier transform infrared spectroscopy (FTIR) indicated that the rate of monomer disappearance under SFRP and thermal conditions were identical. This observation indicated a lack of control in the presence of the stable free radical, TEMPO. The similarities in chemical structure between styrene and 2-vinylnaphthalene suggested thermally initiated polymerization occurred via the Mayo mechanism. A kinetic analysis of the thermal polymerization of styrene and 2-vinylnaphthalene suggested that the additional fused ring in 2-vinylnaphthalene increased the propensity for thermal polymerization. The observed rate constant for thermal polymerization of 2-vinylnaphthalene was determined using in situ FTIR spectroscopy and was one order of magnitude greater than styrene, assuming pseudo-first-order kinetics. Also, an Arrhenius analysis indicated that the activation energy for the thermal polymerization of 2-vinylnaphthalene was 30 kJ/mol less than styrene.

Block copolymerization initiated by Ce(IV)-poly(ethylene glycol) redox system—kinetics and characterization

The kinetics of ceric ion-poly(ethylene glycol) (PEG, mol. wt 6000) redox-coupled-initiated polymerization of acrylonitrile (M), yielding a block copolymer of PEG and poly(acrylonitrile) (PAN) in aqueous sulphuric acid medium, has been investigated. The polymerization experiments were conducted in the dark under a nitrogen atmosphere in the temperature range 35–60°. The polymerization was found to proceed without an induction period. The rate of monomer disappearance was found to be dependent on [M] 2, [PEG] and independent of both [Ce(IV)] and [H +]. The rate of ceric ion disappearance was directly proportional to [Ce(IV)] and [H +] but independent of [M]. The FT-i.r. spectra of the block copolymer showed the presence of both PEG and PAN segments. The elemental analysis indicated the molar composition of PAN and PEG in the block copolymer to be 80:20.

Cerium(IV)-sorbose-initiated polymerization of acrylamide and methacrylamide

The kinetics of the aqueous polymerizations of acrylamide and methacrylamide employing the cerium(IV) ammonium nitrate-sorbose redox pair under an inert atmosphere were studied. It was found that the rate of monomer disappearance is directly proportional to the concentration of sorbose and inversely proportional to the cerium(IV) ion concentration but depends on the square of the monomer concentration. The rate of cerium(IV) ion disappearance is directly proportional to the initial concentration of cerium(IV) ion and sorbose but independent of the monomer concentration. The effects of various additives, namely alcohols, inorganic salts and so on, on the rates of polymerization of acrylamide and methacrylamide were also studied. The viscometric average molecular weight M ̄ v decreases on increasing the concentration of monomer and sorbose. A plausible mechanism based on experimental results is proposed.

Greffage de monomères acryliques induit par un plasma froid sur un polypropylène

AbstractCold plasma can be applied to polymer chemistry especially when grafting is to be achieved. Multifunctional acrylate monomers could be grafted onto polypropylene after its surface was activated. Grafting, the final stage of this plasma‐induced polymerization, is the consequence of a reaction of a macroradical, which has diffused to the surface of the substrate, with a reactive species created on the polypropylene surface. The rate of grafting was found to be smaller than the rate of monomer disappearance. The rate increases with the power, but no relation could be established between both.

Kinetics of polymerization of vinyl monomers initiated by lead tetraacetate

AbstractA systematic study of the thermal polymerization of α‐chloroacrylic acid and α‐bromoacrylic acid in aqueous nitric acid was carried out. The effect of variation of monomer concentration lead tetraacetate concentration, hydrogen ion concentration, ionic strength, and temperature on the rate of monomer disappearance was carried out. Based on the experimental observations, suitable reaction schemes were proposed for the polymerization of the above monomers. The rate constants and the thermodynamic parameters were evaluated.

Aqueous Polymerization of Methacrylamide Initiated by Glycolic Acid-Ceric Ammonium Sulfate Redox System

Abstract The aqueous polymerization of methacrylamide (MA) initiated by the glycolic acid (GA)-Ce(IV) redox system was studied in sulfuric acid medium at 35 ± 0.2°C under a nitrogen atmosphere. The rate of monomer disappearance was found to be proportional to [MA]1 [Ce(IV)]1/2 [GA]1/2, and the rate of ceric ion disappearance was proportional to [GA] and [Ce(IV)] but independent of [MA]. The rate of polymerization increased with increasing temperature in the 30 to 50°C range. The activation energy was found to be 43 kJ/mol. The effect of increasing [H2SO4] on the polymerization was also studied. A kinetic scheme involving initiation by free radicals generated from the redox reaction between GA and Ce(IV) and termination by bimolecular reaction of macroradicals has been suggested.

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

AbstractThe 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 (Mv) 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.

Polymerization of Methacrylamide Initiated by Ceric Ion-Citric Acid Redox System

Abstract Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]0.4, [Ce0.4+]0.65, and [Monomer]1 The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H2SO4]. The activation energy of the system was found to be 21.4 kJ/mol.

Aqueous polymerization of methacrylic acid initiated by Ce4+ ‐glycolic acid redox pair

AbstractThe aqueous polymerization of methacrylic acid (MAA) initiated by a Ce4+ ‐glycolic acid (GA) system was observed in a sulfuric acid medium at 35 ± 0.2°C in a nitrogen atmosphere. The rate of monomer disappearance was proportional to [MAA]1 and the rate of ceric ion disappearance was proportional to [GA][Ce4+]. An increase in the reaction temperature from 30 to 45°C raised the rate and the overall activation energy was 63 kJ/mol. The molecular weight increased with a rise in [MAA] and a reduction in [Ce4+]. The effect of varying [H2SO4] was also studied.

Aqueous Polymerization of Methyl Methacrylate Initiated by Ce4+-Glycolic Acid Redox System

Abstract The aqueous heterogeneous polymerization of methyl methacrylate (MMA) initiated by the Ce4+-glycolic acid (GA) redox system was studied at 35 × 0.2°C under a nitrogen atmosphere. The rate of monomer disappearance was proportional to [MMA]1[GA]1[Ce4+]°, and the rate of eerie ion disappearance was found to be directly proportional to [Ce4+] and [GA] but independent of [MMA]. The activation energy was found to be 34 kJ/mol. The molecular weight of polymethyl methacrylate increased with increasing [MMA] and decreased with increasing [oxidant]. The effect of increasing [H2SO4] on polymerization was also studied. The results are compared with those obtained for the aqueous homogeneous polymerization of acrylamide with the same redox pair.

Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system

AbstractHeterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]0, [Ce4+]0.63, and [Monomer]1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H2SO4]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.

Kinetics of Polymerization of Ethyl Acrylate Initiated by Manganese(III)

Abstract The kinetics of the thermal polymerization of ethyl acrylate initiated by Mn3+ in sulfuric acid at 50 to 60°C have been studied. The rate of monomer disappearance is found to bear a square dependence on [M] and is independent of both [Mn3+] and [H+]. The rate of manganic disappearance is found to be directly proportional to [M], [Mn3+], and [H+]. The degree of polymerization is directly proportional to [M] and inversely proportional to [Mn3+] and [H+]. A kinetic scheme involving the initiation and termination of polymerization by Mn3+ is proposed.

Polymerization of acrylamide with ceric ion–malic acid redox pair

AbstractThe polymerization of acrylamide (M) in aqueous sulfuric acid medium initiated with ceric ammonium sulfate–malic acid redox pair was investigated at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and malic acid (MA). The rate of monomer disappearance was proportional to the first power of malic acid, ceric ion, and monomer concentrations at lower ceric ion concentrations. However, at higher ceric ion concentrations the rate was independent of [Ce(IV)]. The rate of ceric ion disappearance was proportional to [MA] and [Ce(IV)] but independent of [M] at lower ceric ion concentrations. The activation energy was found to be 57.74 kJ/mol. Sulfuric acid retarded the reaction. Molecular weights increased with increasing [M] and decreasing [Ce(IV)].

Kinetics of photopolymerization of acrylamide initiated by copper (II)–bis(amino acid) chelates in aqueous solution. II

AbstractThe kinetics of photopolymerization reactions of acrylamide initiated by copper (II)–bis(amino acid) chelates with amino acids glutamic acid, serine, or valine were studied at 30°C. The extent of monomer conversion increases with increased initiator concentration and falls off after reaching a maximum. Analysis of the results shows that for lower concentrations of the initiator, the rate of monomer disappearance is proportional to light absorption fraction f[monomer] and the square root of the intensity. At higher concentrations of the initiator, the rate of monomer disappearance is proportional to Fε/[initiator]1/2; the monomer exponent is 1.5 and the intensity exponent 0.5. Mutual termination of the radicals is proposed at lower concentrations of the initiator; at higher concentrations of the initiator termination of the initiator radical by the copper (II) complex along with mutual termination occurs. The initiator radical species is identified from flash photolysis studies of these complexes as the Cu(I)‐coordinated radical. The effect of pH on the monomer conversion is explained. The data indicate a free‐radical mechanism of polymerization and a reaction scheme is proposed for the polymerization reactions.

Ceric‐ion‐initiated polymerization of acrylonitrile in the presence of sucrose

The polymerization of acrylonitrile was studied in aqueous sulfuric acid with the redox initiator system, ceric ammonium sulfate/glycerol at 15-25°C. The initiation was effected by the ceric ion and the radical produced from the reaction of Ce 4+ with glycerol. At lower concentrations of Ce 4+ , the rate of monomer disappearance was proportional to [M] 1,5 , [G] 0,5 , and [Ce 4+ ] 0,5 , and the rate of ceric ion disappearance was directly proportional to [Ce 4+ ] and [G]. The results were explained by a kinetic scheme involving the oxidation of substrate by Ce 4+ to give the primary radical and further reaction of the latter with Ce 4+ to give the final product, and initiation of polymerization both by Ce 4+ and the primary radical. The initiation by Ce 4+ was found to be negligible as compared to that by the primary radical. The termination step is postulated to be mutual at lower concentrations of Ce 4+ and linear at higher concentrations of Ce 4+ . The induction period and the rate of polymerization was compared with those of other polyol systems, such as sorbitol and mannitol.

Polymerization of acrylonitrile initiated by ceric ion-organic sulphur compounds reducing agent systems

Polymerization of acrylonitrile was investigated using ceric ion-organic sulfur compounds reducing agent systems. The organic sulphur compounds used as the reductants are, thiourea, thioacetamide, 2-amino ethanethiol, cysteine, and thioglycolic acid. The rates of polymerization were measured within the temperature range of 25 to 40 °C. The initiation was by the radical produced from Ce4+-sulphur compounds reaction. The rate of monomer disappearance was proportional to [M]1.5, [S]0.5 and the rate of ceric disappearance was directly proportional to [S] and [Ce4+]. A kinetic scheme involving the initiation by the primary radical and termination of the growing polymer radicals by the mutual type has been suggested and the kinetic percentage have been evaluated.

Photopolymerization of methyl methaerylate initiated by benzil in non-aqueous media

Kinetics of polymerization of methyl methacrylate initiated by photolysis of benzil with 420 nm radiation, have been investigated at 35 °C. The rate of monomer disappearance has been followed gravimetrically and the chain-length of the polymer formed, measured by viscometry. The dependence of the rate of polymerization and quantum yield of monomer conversion on the concentrations of the monomer and the initiator, absorbed light-intensity etc. has been studied in detail. A kinetic scheme has been proposed in the light of experimental results, involving i) a primary photochemical act of excitation of the sensitizer producing free radicals by hydrogen abstraction, ii) initiation of polymerization by free radicals generated and iii) termination of the active chain by mutual combination involving either coupling or disproportionation.

Studies on aqueous polymerization of acrylonitrile. Cerium(IV)/acetaldehyde redox system

AbstractThe thermal polymerization of acrylonitrile initiated by the cerium(IV)/acetaldehyde (A) redox system was carried out at 25°C, and the rate of monomer disappearance, –d[M]/dt, was followed by gravimetry and the rate of cerium(IV) disappearance –d[Ce(IV)]/dt by titrimetry. –d[M]/dt was found to be directly proportionsl to [M]3/2, [A]1/2, and [Ce(IV)]1/2. –d[Ce(IV)]/dt was found to be directly proportional to [Ce(IV)] and [A]. A reaction scheme is given together with the kinetic expressions. The activation energy for the overall rate was found to be 67,24kJ.mol−1 (16,06kcal.mol−1), and the value of the second order rate constant kr, was obtained as 2,481.mol−1s−1.

Mechanism of the polymerization of acrylamide initiated by the glycerol/Ce(IV) redox system

AbstractThe mechanism of the polymerization of acrylamide in aqueous medium initiated by the glycerol (R)/Ce(IV) redox system was studied. The rate of monomer disappearance was found to be directly proportional to [M]3/2, and R1/2 at lower concentrations of Ce(IV). The rate of the disappearance of ceric ions was found to be inversely proportional to [M] and directly proportional to [Ce(IV)] and [R]. Consistent with the findings of earlier investigations, a complex formation between monomer, acrylamide, and ceric ion is indicated. The experimental results show the termination to be mutual. On the basis of these and other kinetic results, an appropriate mechanism is proposed. At higher concentration of Ce(IV), a different mechanism seems to operate. The rates of disappearance of both the monomer and ceric ions are retarded on addition of anions like HSO4−, SO4− −, or CIO4−, but they are accelerated on the addition of Mn(II) ions. Interpretations of the above observations are furnished.