Polymerization of Methacrylamide Initiated by the Persulfate/Thiolactic Acid Redox System

The aqueous polymerization of methacrylamide initiated by the ammonium persulfate/thiolactic acid redox system has been studied at 35 ± 0.2°C. The rate of polymerization is governed by the expression, R_p + K_p [MAA] ^1.33 [TLA]^0.22 [ammonium persulfate]^0.6. The deviations from normal kinetics are discussed. A tentative mechanism of initiation is given. The temperature dependence of the rate of polymerization has been studied over the range 30–55°C. The overall activation energy of polymerization is 10.4 kcal/mole.     

Permanganate-Pyruvic Acid Initiated Polymerization of Methacrylamide

A combined system of potassium permanganate and pyruvic acid was found to initiate radical polymerization of vinyl monomers, especially acrylamides. From kinetic investigations of the polymerization of methacrylamide, it was found that this initiator induced a radical polymerization which proceeded with an overall activation energy of 15.7 kcal/mol. The rate is given by

R_p=K[methacrylamide] ¹ [pyruvic acid]° [KMnO₄]¹ in aqueous and water-DMF mediums. In the presence of DMF the initial rate was found to decrease but the kinetic equation remained the same. The investigations were done at 35 ± 0.2°C in nitrogen.

Besides the clinical importance of pyruvic acid found in blood, urine, muscles, etc., it is a good initiator in conjunction with KMnO₄ for vinyl polymerization. It is therefore interesting to study the polymerization of methacrylamide using the KMnO₄-pyruvic acid redox couple in aqueous systems in order to find whether this system follows the same kinetic features of vinyl polymerization by a radical mechanism.     

Vinyl Polymerization of Ethyl Acrylate Initiated by TI3+-Ascorbic Acid Redox System

The application of polymers at ever-increasing temperatures has given impetus to research on the chemistry of thermal decomposition. In recent years polymers have been used for a variety of high-temperature applications, such as cooking vessels, motor insulation, and re-entry vehicle heat shields. Interest in chemistry of decomposition has been found in such industries as tobacco and grinding-wheels. Because of the vast number of polymers that are available and the variety of applications thousands of papers have appeared in the literature. Rather than give a complete review the purpose of this paper is to give a brief survey of topics that have been emphasized in the author's research, namely kinetics, mechanisms, and gaseous decomposition products at elevated temperatures.     

The NMR Spectra of Styrene-Itaconate Ester Copolymers Obtained by Free Radical Mechanism

Styrene copolymerized with dimethyl itaconate and with methyl benzyl itaconate by use of a free radical initiator.

Monomer reactivity ratios for styrene (M₁)-dimethyl itaconate (M₂) co-polymerization were r₁ = 0.50 and r₂ = 0.06 and for styrene (M₁-methyl benzyl itaconate (M₂), r₁ = 0.42 and r₂ = 0.19. The nonconjugative methoxycarbonyl affected the monomer reactivity of itaconate toward polystyrene radical.

The NMR spectra of styrene-dimethyl itaconate copolymers were very complex and could not be interpreted because the two methoxy groups have similar chemical shifts.

The NMR spectra of styrene-itaconate copolymers were not so complex if methyl benzyl itaconate was used as comonomer instead of dimethyl itaconate. Methoxy and benzyloxy absorptions were sufficiently separated and “co-isotacticity” could be determined.

It is shown that the nonconjugative methoxycarbonyl group had little influence on the steric course of the cross-propagation reaction between styrene and itaconate.     

Pentavalent Vanadium-Ascorbic Acid Redox System Initiated Polymerization of Acrylonitrile

Kinetics of polymerization of acrylonitrile initiated by the redox system V⁵⁺ascorbic acid were investigated in aqueous sulfuric acid in the temperature range of 35–50°C, and the rates of polymerization, of V⁵⁺/disappearance, etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V⁵⁺ - ascorbic acid complex formation followed by subsequent decomposition and terminated by V⁵⁺ions. A suitable kinetic scheme was proposed and the various rate parameters were evaluated.     

Kinetics of Aqueous Polymerization of Acrylamide Initiated by Ceric Ammonium Sulfate/2-Mercaptoethanol Redox System

Polymerization of acrylamide monomer, initiated by the redox system involving acidified ceric ammonium sulfate and 2-mercaptoethanol (2-ME) was carried out in an aqueous medium at 25° C. White, rigid polyacrylamide, isolated under controlled experimental conditions, showed a molecular weight of 1.5 × 10⁴ from viscosity measurements. The rate of monomer (M) conversion to polymer was found to be proportional to [M]^1.5, [2-ME]^0.5, and [Ce(IV)]^0.4. Further, the rate of disappearance of ceric ion was observed to be directly proportional to [2-ME] and independent of [M] in the range of 0.16–0.48 mole/liter. The explanation of the above proportionalities is given in terms of a proposed reaction mechanism. Values of the usual rate constants, k_r, k₀/k_t and k_t./k_p ^½ have been computed.     

Vinyl Polymerization Initiated by Peroxydiphosphate. XI. Polymerization of Methyl Methacrylate Initiated by Peroxydiphosphate-Tartaric Acid Redox System

The polymerization of methyl methacrylate was studied using the peroxydiphosphate and tartaric acid redox system as the initiator. 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 reaction was carried out at three different temperatures, and the overall activation energy was computed to be 3.80 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been proposed.     

Aqueous Polymerization of Methyl Methacrylate Initiated by Potassium Peroxydisulfate-Ascorbic Acid Redox System

The aqueous polymerization of methyl methacrylate initiated by the redox system K₂S₂O₈-ascorbic acid has been studied at 35°C under the influence of oxygen. The rate of polymerization increases with increasing ascorbic acid concentration at low activator concentration, remains constant within the range 4.375 × 10^?3 to 11.25 × 10^?3 mole/liter, and at higher ascorbic acid concentration again decreases. The rate varies linearly with monomer concentration. The initial rate and the limiting conversion increase with increasing polymerization temperature. Organic solvents (water-miscible only) and small amounts of neutral salts like KC1 and Na₂SO₄ depress the initial rate and the maximum conversion. The addition of small amounts of salts like Cu²⁺ and Mn²⁺ increases the initial rate, but no appreciable increase in the limiting conversion is observed.     

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.     

铈离子氧化还原引发体系与铈离子引发接枝或嵌段共聚合研究的新进展

本文介绍Ce⁴⁺/酰胺引发体系;Ce⁴⁺/聚酰胺、带酰苯胺侧基的聚合物引发接枝共聚合;Ce⁴⁺/氨基甲酸酯引发体系;Ce⁴⁺/聚醚氨酯引发接枝共聚合;Ce⁴⁺/羰基化合物引发体系;Ce⁴⁺引发嵌段共聚合6个方面的研究新进展.     

Vinyl Polymerization Initiated by Peroxydiphosphate. IV. Polymerization of Acrylonitrile Initiated by Peroxydiphosphate-Thioacetamide Redox System

Abstract

The kinetics of the aqueous polymerization of acrylonitrile initiated by the peroxydiphosphate-thioacetamide redox system was investigated at 35, 40, and 50°C. The rates of polymerization were measured at different concentrations of oxidant, activator, and monomer. Peroxydiphosphate alone did not initiate polymerization under deaerated and undeaerated conditions. Addition of certain water-miscible organic solvents and neutral salts depress the rate and conversion. On the basis of experimental observations of the dependence of the rate of polymerization on various variables, a suitable kinetic scheme has been proposed.     

Acrylonitrile Polymerization by Ceric lon-Primary Alcohol Redox Systems in Aqueous Nitric Acid

The polymerization of acrylonitrile (AN) initiated by Ce^IV-primary alcohol redox systems has been studied in aqueous nitric acid under nitrogen in the temperature range 0 to 45° C. Taft's correlation can be applied to fit the kinetic results relative to a series of differently substituted primary alcohols. The polymerization is initiated by primary radicals formed in water from the dismutation of the Ce^IV -alcohol complex, This process has a high activation energy (21 kcal/mol) and gives rise to an induction period at temperatures lower than 40° C. PAN chains containing the alcohol residue are terminated predominantly on metal ions. The alcohol enhances the AN solubility in water and accordingly influences the polymerization kinetics. Variations in temperature and concentration of both components of the redox system allow control of the polymerization rate and of the molecular weight of the resulting PAN.     

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

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.     

Aqueous Polymerization of Acrylamide Initiated by Glycolic Acid/Ce4+ Redox System

The aqueous polymerization of acrylamide initiated by the glycolic acid/Ce⁴⁺ redox system was studied in sulfuric acid medium at 35 ± 0.2°C under a nitrogen atmosphere. The initiation was carried out by the free radical generated in the decomposition of the complex formed between the oxidant and the reductant. The monomer disappearance was found to be proportional to [GA]^0,89[Ce⁴⁺]^0.57[M]^1.0, and the rate of ceric ion disappearance was found to be directly proportional to [Ce⁴⁺] and [GA] but independent of [M]. The activation energy of the system was found to be 7.21 kcal/deg/mol. The molecular weight of polyacrylamide increased with increasing [monomer] and decreased with increasing [catalyst]. The effect of pH was also studied in the pH range 2.22 to 1.44.     

Aqueous Redox Polymerization of Acrylamide Initiated by Lactic Acid/Permanganate

Acrylamide was polymerized in aqueous solution at 35 ± 0.2°C with the redox pair potassium permanganate/lactic acid. The kinetics of polymerization was followed iodometrically. The effect of monomer, potassium permanganate, and lactic acid concentration and temperature on the rate of polymerization was studied. The dependence of the number-average degree of polymerization on the initial rate of polymerization and temperature was also determined.     

Hexavalent Chromium-Thioacetamide Redox System Initiated Polymerization of Acrylonitrile

Polymerization of acrylonitrile initiated by the Cr⁶⁺/thioacetamide redox system was studied in nitrogen atmosphere in the temperature range 35–45°C. The rate of polymerization and the rate of Cr⁶⁺ ion disappearance were measured. The effect of certain water-miscible organic solvents, neutral electrolytes, and complexing agents on the rate of polymerization was investigated. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. Depending on the results obtained, a suitable kinetic scheme was proposed and various rate parameters were evaluated.     

Redox Polymerization of Acrylonitrile: Kinetics of the Reaction Initiated by the Redox System 1-Propanol—Chromic Acid

The kinetics of the aqueous polymerization of acrylonitrile initiated by the chromic acid-1-propanol redox system was investigated under a nitrogen atmosphere. The rates of polymerization and the disappearance of Cr(VI) were measured. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. Water-miscible organic solvents and neutral salts depress both the rate and the conversion. On the basis of the experimental observations of the dependence of the rate of polymerization R_p and the rate of disappearance of Cr(VI)-R_m on various variables, a suitable kinetic scheme was proposed and various rate and energy parameters evaluated.     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Bromate-Thiourea Redox System

The aqueous polymerization of methyl methacrylate initiated by the bromate-thiourea redox system in dilute HC1 has been investigated under nitrogen atmosphere. The rate of polymerization increases with increasing concentration of thiourea in the range 5 × 10^?3?10 × 10^?3 M. The percentage of conversion increases with increasing concentration of the catalyst, but beyond 1.5 × 10^?2 M, there is a decreasing trend in the rate of polymerization. The rate of polymerization increases with increasing monomer concentration, but beyond 0.184 M the polymerization rate decreases due to gel effect. The rate of polymerization increases with temperature up to 35°C and beyond 40°C a decreasing trend is noticed. The effect of water miscible organic solvents, certain neutral salts on the rate of polymerization has also been investigated.     

Polymerization of Acrylonitrile Initiated by the Thiourea-Mn3+ Redox System

Kinetics of vinyl polymerization initiated by the redox system thiourea-Mn³⁺ were investigated in the temperature range 30–40°C in sulfuric acid, and the rates of polymerization R_p and disappearance of Mn³⁺ have been measured. The effect of certain water-miscible organic solvents and anionic surfactant on the rates of polymerization was investigated. A mechanism involving the formation of a complex between Mn³⁺ and thiourea whose decomposition yields the initiating free radical with the polymerization terminated by mutual intraction of growing radicals is suggested.     

Vinyl Polymerization Initiated by Metal Chelates. III. Polymerization of Methyl Methacrylate Initiated by Vanadium(IV) Acetylacetonate Chelates

The polymerization of methyl methacrylate initiated by the vanadium acetylacetonate complex was investigated under a nitrogen atmosphere at 50°C. The effect of concentration of monomer, complex, acid, dioxane, inhibitor, and the effect of temperature on the rate of polymerization were studied. The rate of polymerization was found to increase upon increasing the concentrations of the monomer, the initiator, and the acid. The overall activation energy has been computed from the Arrhenius plot and a suitable kinetic scheme has been proposed.