Cationic Polymerization of Isobutyl Vinyl Ether in Solution by Radiation

The radiation-induced cationic polymerization of isobutyl vinyl ether in solutions of diethyl ether and methylene chloride was investigated under conditions where the monomer and solvents were dried with molecular sieves to high levels of dryness. The investigation covered the temperature range from -16 to 90° C, the dose-rate range from 10¹⁵ to 10²⁰ eV/ (g)(sec) (using both gamma rays and electrons), and the influence of diethyl ether and methylene chloride as solvents for the monomer.

For the solution of the monomer in diethyl ether, a very high overall activation energy of 29.7 kcal/mole was found, which decreased sharply to a value of 1.2 kcal/mole above 30° C. No such change was found for the monomer solution in methylene chloride.

The dose-rate dependence of the rate of polymerization for the monomer solution in methylene chloride was found to be close to unity over the entire dose-rate range investigated.     

Polymerization of Acrylamide with Permanganate/Mercaptosuccinic Acid Initiator System

The aqueous polymerization of acrylamide initiated by the acidified potassium permanganate/mercaptosuccinic acid redox system was studied at 35 ± 0.2°C in nitrogen. In the studied range of activator concentration (2.0 × 10^?3 to 6.25 ± 10^?3 mole/liter) the polymerization rate remains unaffected. The initial rate of polymerization varies linearly with KMnO₄ and acrylamide concentrations in the studied range. The activation energy was found to be 6.61 kcal/mole (27.63 kJ/mole) in the temperature range of 30–50°C. The molecular weight of polyacrylamide was found to be independent of [KMnO₄] but increased with increasing monomer concentration. The effect of DMF on polymerization rate and molecular weight was also investigated.     

Polymerization of α-amino acid N-carboxy anhydrides. III. Mechanism of polymerization of L- and DL-alanine NCA in acetonitrile

The polymerization of L - and DL -alanine NCA initiated with n-butylamine was carried out in acetonitrile which is a nonsolvent for polypeptide. The initiation reaction was completed within 60 min.; there was about 10% of conversion of monomer. The number-average degree of polymerization of the polymer obtained increased with the reaction period, and it was found to agree with value of W/I, where W is the weight of the monomer consumed by the polymerization and I is the weight of the initiator used. The initiation reaction of the polymerization was concluded as an attack of n-butylamine on the C₅ carbonyl carbon of NCA. The initiation, was followed by a propagation reaction, in which there was attack by an amino endgroup of the polymer on the C₅ carbonyl carbon of NCA. The rate of polymerization was observed by measuring the CO₂ evolved, and the activation energy was estimated as follows: 6.66 kcal./mole above 30°C. and 1.83 kcal./mole below 30°C. for L -alanine NCA; 15.43 kcal./mole above 30°C., 2.77 kcal./mole below 30°C. for DL -alanine NCA. The activation entropy was about ?43 cal./mole-°K. above 30°C. and ?59 cal./mole-°K. below 30°C. for L -alanine NCA; it was about ?14 cal./mole-°K. above 30°C. and ?56 cal./mole-°K. below 30°C. for DL -alanine NCA. From the polymerization parameters, x-ray diffraction diagrams, infrared spectra, and solubility in water of the polymer, the poly-DL -alanine obtained here at a low temperature was assumed to have a block copolymer structure rather than being a random copolymer of D - and L -alanine.     

Ferric oxide-catalyzed polymerization of methyl methacrylate

The polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10^?5 mole/l.-sec to 11.8 × 10^?5 mole/l.-sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 10⁶ in the absence of ferric oxide to 2.8 × 10⁵ when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 10⁵ at 30°C to 2.2 × 10⁵ at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 10⁴ to 5.3 × 10⁵ and from 3.4 × 10⁵ to 8.9 × 10⁵ as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferric oxide, respectively.     

Evidence for several species of active sites in Ziegler-Natta catalysts

The kinetics of isoprene polymerization catalyzed by VCl₃ and Et₃Al were studied by measuring fractional conversions, polymer composition, and molecular weight distributions at a series of reaction times and temperatures. The rate of polymerization plotted against temperature shows an inflection point with a minimum and maximum in the 60–90°C range. The isomeric composition of the polymer changes with temperature but not with reaction time, while the molecular weight distribution undergoes substantial change with both of these variables. The rate of polymerization at sites producing low molecular weight polymers was measured, and the activation energy calculated to be about 10 kcal/mole. The active sites were found to deactivate at different rates. The results support the hypothesis that several species of active sites are present in the system and that these exhibit characteristic polymerization behavior.     

Molecular weight distributions in radiation-induced polymerization. III. γ-Ray-induced polymerization of styrene at low temperatures

The kinetics of the γ-radiation-induced polymerization of styrene was studied at radiation intensities of 8 × 10⁴, 2.4 × 10⁵, 3.1 × 10⁵, and 8.3 × 10⁵ rad/hr over a temperature range of ?10°C to 30°C. The water content of the irradiated samples varied from 1.0 × 10^?3 to 7.5 × 10^?3 mole/l. The power dependence of the rate of polymerization on the dose rate at ?10°C varied from 0.53 to 0.71 as the water content of the sample varied from 7.5 × 10^?3 to 1.0 × 10^?3 mole/l. A value of 3.1 kcal/mole was determined for the overall activation energy. Molecular weight distribution studies by gel-permeation chromatography indicated the presence of two distinct peaks. The contribution of each peak was dependent on specific experimental parameters. Kinetic data and molecular weight distribution data indicate the coexistence of two propagating species. Analysis of the data strongly suggests that a free-radical mechanism and a cationic mechanism are involved.     

Polymerization of Acrylonitrile Initiated by 1,4-Dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene

The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]^0.64 and [AN]^1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are k_d = 2.78 × 10^?6 sec^?1, ΔH^? = 40.8 kcal/mole, and ΔS^? = 19.5 cal/mole-deg, respectively.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. VI. Effects of pressure and temperature

In a radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene, the effects of pressure and temperature were investigated in the range of 0–40 kg/cm² and 7–53°C at emulsifier concentration of 0.5 and 2.0%. Both the polymerization rate and the molecular weight of copolymer increase with increasing pressure and decreasing temperature. These facts are mainly due to an increase of the monomer concentration in the polymer particles. The rate of polymer chain formation was found to be independent of pressure and temperature. The initiation reaction is due mainly to the entry of radicals generated in the aqueous phase into the polymer particles. The apparent activation energy is ?2.0 to ?3.8 kcal/mole for the polymerization in the presence of 0.5% emulsifier, but is nearly zero at an emulsifier concentration of 2.0%. This difference in apparent activation energies at emulsifier concentrations of 0.5 and 2.0% is explained in terms of the termination mechanisms.     

The Thermal Dimerization and Polymerization of 1,3-Cyclohexadiene

Abstract

The thermal polymerization of 1,3-cyclohexadiene to produce dimer and low molecular weight polymer is reported. The reaction initiated thermally and/or by benzoyl peroxide is kinetically of the second order, and the activation energy is 13.1 kcal/mole. The activation energy for the reaction is in quantitative agreement with that of the homopolymerization of 1,3-cyclohexadiene estimated from the kinetic study on the copolymerization with acrylonitrile. Evidently the dimerization process to give dimer as a product of typical Diels-Alder condensation is a competing type of reaction with radical polymerization to give a low molecular weight polymer. The ratio of the rate constant for two competing types of reaction at 200°C is found to be 1.21. The thermal polymerization in the presence of oxygen produces dimer in greater yield as a result of inhibition of the radical polymerization process.     

The Effect of Active Carbon on the Kinetics of Polymerization of Methyl Methacrylate

Rates of 2–2¹?azobisisobutyronitrile initiated polymerization of methyl methacrylate in benzene were determined at 77.2, 65.0, and 50.0°C. The variation of molecular weight of the polymer with temperature and conversion was also studied. At a fixed conversion of 2.0%, the molecular weight decreased from 2.05 × 10⁵ at 50°C to 1.4 × 10⁵ at 77.2°C. The ratio of the propagation rate coefficient to the square root of the termination rate coefficient was found to be 0.61, 0.397, and 0.374 at 77.2, 65.0, and 50.0°C, respectively, with an uncertainty of ±0.5°C in temperature. The effect of active carbon on the rates of polymerization at 77.2°C was measured. Rates of polymerization decreased in the presence of active carbon. For example, the initial rate of polymerization decreased from 7.8 × 10^?4 mole/(liter min) to 4.6 × 10^?4 mole/(liter min) when the carbon concentration was varied from 0 to 9.65 g/liter. The molecular weight of the polymer increased from an average of 1.4 × 10⁵ in the absence of carbon to 1.5 × 10⁵ when carbon was present.     

Proposed Participation of Excited Monomer in the Free Radical-Catalyzed High Pressure,High Temperature Polymerization of Ethylene

The radiation-induced copolymerization of ethyl vinyl ether with dibutyl maleate was investigated over a wide range of comonomer compositions, dose rates, and in the temperature range from ?25 to 75° C. Both the rates of copolymerization and the molecular weights of the resulting copolymers were found to depend strongly on the initial comonomer composition, both reaching a maximum value at an equimolar comonomer composition. A copolymer was obtained in which the co-monomers alternate with regularity along the polymer chain over the entire range of comonomer compositions investigated. The monomer reactivity ratios were determined and found to be practically zero. The apparent activation energy was found to change at 35° C, the boiling point of the ethyl vinyl ether, from a value of 10.48 kJ/mole to a value of 18.86 kJ/mole above this temperature. This phase change also resulted in a marked decrease in the molecular weights of the copolymers formed above 35° C. The dose-rate dependence of the rate of copolymerization was found to be 0.70 over the dose-rate range     

Radiation-Induced Polymerization of Tetrafluoroethylene

Polymerization of tetrafluoroethylene was carried out in bulk at low temperatures by initiation with γ-rays from a ⁶⁰ Co source. It was found that a remarkable postpolymerization takes place even in the liquid phase. Kinetical analysis has been made of the in-source and postpolymerizations. An activation energy of 2.7 kcal/mole was obtained for the in-source polymerization and 10.3 kcal/mole for the postpolymerization. The long lifetime of polymer radicals in the liquid phase at -78°C seems to be due to the slow recombination rate of the polymer radicals, based on the rodlike shape of the polymer radicals.     

Kinetic study of dissolution of poly(vinyl chloride) in cyclohexanone

The kinetics of dissolution of five fractions of commercial poly(vinyl chloride) in cyclohexanone was studied at temperatures from 20 to 70°C. Good agreement was observed between the experimental results and equations expressing the dependence of the induction periods and the rates of dissolution on temperature and molecular weight. It was found that the apparent activation energy for the swelling process lies in the range 9–14 kcal/mole and the apparent activation energy for the dissolution diffusion process in the range 8–12 kcal/mole. The apparent dependence of activation energies on number-average molecular weight indicates that the chain ends are more important in determining the dissolution rate than the centers of the polymer chains.     

Radiation-induced heterogeneous polymerization of methyl methacrylate in precipitants

The radiation-induced heterogeneous polymerization of methyl methacrylate in various precipitants, mainly methyl alcohol, was carried out, and the effects of reaction conditions on the polymerization behavior and the molecular weight distribution of polymer were studied. Bimodal molecular weight distributions were found for the polymer produced by the heterogeneous polymerizations in methyl alcohol and in tert-butyl alcohol. The apparent activation energy is 1.0 and 4.5 kcal/mole, respectively, for the polymerization at a monomer concentration of 10 vol-% in methyl alcohol above and below 35°C. The polymerization at a monomer concentration lower than 40 vol-% in methyl alcohol proceeded with the precipitation of polymer. The dose rate exponent of the mean rate of heterogeneous polymerization decreased from 0.5 to a smaller value as the polymerization progressed. The ratio of the two peaks in the bimodal molecular weight distributions of polymer produced in methyl alcohol was affected by the reaction conditions. These results show the coexistence in the polymerizations of two different physical states of propagating chain, a loose state and a rigid one. The reaction scheme is discussed in connection with the physical factors which affect the solubility or the mobility of propagating chains, and the rate of elementary reactions, which influences the degree of propagating chains.     

Precipitation polymerization of acrylamide using vazo-33 as an initiator and acetonitrile/water mixtures as the solvent

Precipitation polymerization of acrylamide initiated by a thermal initiator, Vazo-33 (DuPont Vazo Initiator), was achieved at a solvent composition of acetonitrile/water = 4/6 (vol/vol). The polymerization kinetics were investigated in the acrylamide [M] concentration range 0.86–2.27M, Vazo-33 [I] concentration range 1.4–11.0 × 10^?4M, and temperature range 30–40°C. Polymerization was carried out in reaction ampules and the rate was determined gravimetrically. Number-average molecular weight was obtained from intrinsic viscosity. The precipitation polymerization rate varied as [M]^2.16 and [I]^0.44. Number-average molecular weight was proportional to [M]^1.22 and inversely proportional to [I]^0.31. The overall reaction activation energy was calculated as 17.3 kcal/mol in the temperature range studied. The optimal reaction conditions studied were: acetonitrile/water = 4/6, temperature = 40°C, [M] = 1.95M and [I] = 2.8 × 10^?4M. One hundred percent conversion was achieved in 90 min and a polymer with a number-average molecular weight of 1,200,000 was obtained.     

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.     

Radiation-induced copolymerization of isobutyl vinyl ether with trichloroethylene

The radiation-induced copolymerization of isobutyl vinyl ether with trichloroethylene was investigated in the temperature range from ?50°C to 100°C over a wide range of comonomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over essentially the entire range of comonomer compositions. Both the rate of copolymerization and the number-average molecular weight of the resulting copolymer were found to depend strongly on the initial comonomer composition. The monomer reactivity ratios were determined and correspond well with calculated values. An apparent activation energy of 3.2 kcal/mole was obtained for the copolymerization process which exhibits a dose rate dependence of 0.72. The number-average molecular weight was found to be strongly dependent on the irradiation temperature, reaching a maximum value at 5°C.     

Radiation-induced solid-state polymerization of derivatives of methacrylic acid. II. Postirradiation polymerization of octadecyl methacrylate

Octadecyl methacrylate (mpc ≈ 12°C.) polymerized readily in the solid state in the temperature range ?30 to +12°C. after gamma irradiation at ?196°C. The initial rate of polymerization and the “limiting” conversion increased with radiation dose and temperature. The temperature dependence of the rate corresponded to an “apparent” activation energy of 20 kcal./mole. Difficulties were experienced with polymerization during separation of the polymer from residual monomer, but these were minimized by using low radiation doses and a hot, selective solvent. The maximum conversion achieved was 70%. The polymer was crosslinked, even at low conversions.     

Aqueous polymerization of methacrylamide

The aqueous polymerization of methacrylamide (I) initiated by KBrO₃–thioglycolic acid (TGA) has been studied at 30 ± 0.2°C in nitrogen. The rate is given by K[M]^1.19 [thioglycolic acid]¹ [KBrO₃]^0.53 for 10–15% conversion. Activation energy was found to be 53.96 kJ/mole (12.92 kcal/mole) in the investigated range of temperature 30–45°C. The role of addition of a series of aliphatic alcohols and some salts was also determined. The kinetics of polymerization was followed iodometrically.     

Studies of redox polymerization. I. Aqueous polymerization of acrylamide by an ascorbic acid–peroxydisulfate system

The polymerization of acrylamide initiated by an ascorbic acid–peroxydisulfate redox system was studied in aqueous solution at 35 ± 0.2°C in the presence of air. The concentrations studied were [monomer] = (2.0–15.0) × 10^?2 mole/liter; [peroxydisulfate] = (1.5–10.0) × 10^?3 mole/liter; and [ascorbic acid] = (2.84–28.4) × 10^?4 mole/liter; temperatures were between 25–50°C. Within these ranges the initial rate showed a half-order dependence on peroxydisulfate, a first-order dependence on an initial monomer concentration, and a first-order dependence on a low concentration of ascorbic acid [(2.84–8.54) × 10^?4 mole/liter]. At higher concentrations of ascorbic acid the rate remained constant in the concentration range (8.54–22.72) × 10^?4 mole/liter, then varied as an inverse halfpower at still higher concentrations of ascorbic acid [(22.72–28.4) × 10^?4 mole/liter]. The initial rate increased with an increase in polymerization temperature. The overall energy of activation was 12.203 kcal/mole in a temperature range of 25–50°C. Water-miscible organic solvents depressed the initial rate and the limiting conversion. The viscometric average molecular weight increased with an increase in temperature and initial monomer concentration but decreased with increasing concentration of peroxydisulfate and an additive, dimethyl formamide (DMF).