Vinyl Polymerization. 282. Vinyl Polymerization Initiated by Dimethylhydroxylamine-Titanous(lll) Chloride Redox System

Abstract

The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]^0.5 for DHA concentrations of less than 2.06 × 10^?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] ^0.58 and to [MMA] ^1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made.     

Vinyl Polymerization Initiated by Sulfur Dioxide

Abstract

A number of monomers have been polymerized in the presence of catalytic and higher concentrations of SO₂. The addition of t-butyl hydroperoxide greatly accelerates the rate of polymerization. The use of ³⁵SO₂ indicates that at catalytic concentrations of SO₂ (10^?2 mole/liter), only one or two molecules of SO₂ are incorporated in the chain, but, at high SO₂ concentrations, copolymerization of SO₂ with vinyl monomers occurs.     

Vinyl Polymerization. 287. Polymerization of Methyl Methacrylate Initiated by the Polyacrylonitrile-Water-Cupric Ion System

Abstract

Methyl methacrylate was found to be polymerized by the system polyacrylonitrile-water-cupric ion without any added initiator. Addition of carbon tetrachloride to this system greatly increased the polymerization rate. Acrylonitrile and styrene did not polymerize in this system. The kinetic behavior of polymerization was the same as the system consisting'of cellulose or nylon instead of polyacrylonitrile. When the flaky polyacrylo-nitrile was swelled or dissolved by the solvent DMF, the conversion and the degree of polymerization of the poly-methyl methacrylate formed decreased markedly. Commercial acrylic fiber also initiated polymerization but the activity was lower than with flaky polyacrylonitrile, even after steam treatment, because of the poor permeability of monomer into the fiber.     

Vinyl Polymerization. 274. Polymerization of Acrylonitrile Initiated by the System Tetramethyl Tetrazene and Co(II) Chloride

Abstract

The binary system of tetramethyl tetrazene (TMT) and Co(II) chloride was used as initiator of acrylonitrile (AN) in dimethylformamide. The initial rate of polymerization (Rp) was found to be expressed by Rp = k[TMT]^0.62[Co(II) chloride]^0.57 [AN]^2.00

The polymerization was confirmed to proceed via a radical mechanism. The over-all activation energy for the polymerization was estimated as 15.1 kcal/mole. On the basis of these results and the product analysis of the reaction between the catalyst components in the absence of monomer, the initiation mechanism of the polymerization is discussed.     

Studies on the Kinetics of Polymerization of Styrene Initiated by Arsenic Trichloride

Abstract

The cationic polymerization of styrene initiated by arsenic trichloride (AsCl₃) in the presence of traces of acetic acid (co-catalyst) at -8, -4, and 0°C for 100 min using the dilatometric technique in an inert atmosphere yielded low molecular weight polymer. The rate of polymerization (R_p) is a direct function of the concentration of AsCl₃, monomer, and polar solvent, but inversely proportional to the polymerization temperature and nonpolar solvent. Hydroquinone has no effect on R_p Various kinetic parameters have been evaluated and a kinetic scheme is proposed.     

Vinyl Polymerization. 269. Polymerization of Methyl Methacrylate Initiated by p,p'-Dimethoxydiphenyldiazomethane

Using p,p'-dimethoxydiphenyldiazomethane (DMDM) as initiator, the polymerization of methyl methacrylate (MMA) in benzene or in bulk was carried out. The initial rate of polymerization, R_p, was found to be expressed by the following equation:

R_p = k[DMDM]^0.53 [MMA]^0.84

The polymerization was confirmed to proceed by a radical mechanism. The over-all activation energy for the polymerization in benzene was calculated as 19.3 kcal/mole. The rate of thermal decomposition of DMDM was also measured in benzene and the rate equation was obtained as follows:

k_d (sec^?1) = 1.0 × 10¹⁵ exp (^?29.1 kcal/RT) (for 50-80°C)

Explanations of these observations are discussed in connection with those of the preceding papers.     

Vinyl Polymerization. 418. Polymerization of Vinyl Monomer Initiated by Betaine-Type Polymers in Aqueous Solution

Abstract

Three kinds of betaine-type polymers, which are macromolecular amphoteric electrolytes, were found to be able to polymerize vinyl monomers in aqueous solution through a radical mechanism without any further initiator. Betain-type polymers form hydrophobic areas (HA) in water. Vinyl polymerization commenced in the HA. The effect of the pH of the aqueous solution on polymerization was investigated.     

Polymerization of Acrylonitrile Initiated by the Mn(III)/Ethane Thiol Redox System

Abstract

Kinetics of vinyl polymerization of acrylonitrile initiated by the redox system Mn(III)/ethane thiol were investigated in aqueous sulfuric acid in the temperature range of 30-45°C. The rate of polymerization, rate of manganic ion disappearance, etc. were measured. The effect of certain water-miscible organic solvents, neutral electrolytes, and organic nitrogen compounds on the rate has been investigated. A mechanism involving the formation of a complex between Mn(III) and the thiol, whose decomposition yields the initiating free radical with the polymerization being terminated by mutual combination of the growing radicals, has been suggested.     

Polymerization of Styrene Initiated by 1,4-Dimethyl-1,4-bis(p-anisyl)-2-tetrazene

Abstract

The polymerization of styrene (St) initiated by 1,4-dimethyl-1,4-bis(p-anisyl)-2-tetrazene (1a) was studied kinetically in benzene. The polymerization proceeds through a radical mechanism. The rate of polymerization is proportional to [1a]^0.5 and [St]^1.0. The overall activation energy for the polymerization is found to be 81.2 kJ/mol within the temperature range of 65 to 80°C. The activation parameters for the decomposition of 1a at 70°C are k_d = 1.88 × 10^?5s^?1, δH? = 133.1 kJ/mol, and δS? = 29.9 J/mol·deg.     

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 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 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.     

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.     

Surface Initiated Polymerization from Nanoparticle Surfaces

Abstract

The synthesis, characterization, and development of new nanoparticle materials have both scientific and technological significance. Surface initiated polymerization (SIP) from nanoparticle surfaces involves the growth of end‐tethered polymer brushes where the length or thickness can be more than twice the radius of gyration (Rg) compared to a free polymer in solution. Different mechanisms are possible on a variety of initiators, reaction conditions, monomers, and nanoparticles. Important differences to solution and bulk polymerization can be observed where the nanoparticles with grafted initiators behave as macroinitiators. In turn, the development of these materials will allow the preparation of thermodynamically and kinetically stable nanocomposites and colloids. Through the careful use of surface sensitive spectroscopic and microscopic techniques, much has been gained from the direct and in‐situ analysis of grafted polymers on the nanoparticles with regards to the kinetics and mechanism of the polymerization process. Parallels can be drawn to SIP on flat surfaces where surface sensitive spectroscopic and microscopic measurements are complementary to analysis methods for colloidal particles. Thus, this review surveys the different polymerization mechanisms and procedures towards forming core‐shell types of hybrid inorganic–organic polymer nanoscale materials.     

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.     

Synthesis of Controlled Block and Graft Copopolymers. II. Block and Graft Polymerization Initiated by Monohalo-Containing Polymer/Manganese Carbonyl Systems

Abstract

Block polymerization of methyl methacrylate initiated with monohalo-terminated polystyrene/manganese carbonyl systems were investigated. The rate of polymerization was lower than that of the trihalo-terminated polystyrenelmanganese carbonyl system. The molecular weight of the block copolymers obtained was independent of the conversion. To define the polymerization mechanism, 1-bromobutane was employed as a model compound for monohalo-terminated polystyrene. Polymerization kinetics followed a modified rate equation based on the Michaelis-Menten mechanism. The molecular weight of the block co-polymer could be regulated by varying the ratio of monohalo-terminated polymer to methyl methacrylate. Graft polymerization of methyl methacrylate initiated with chloromethylstyrene-styrene copolymer/ manganese carbonyl was also carried out. The polymerization behavior was strongly affected by the concentration of manganese carbonyl. Characterization of graft copolymers by GPC and halogen analysis showed that the number of grafting points per backbone polymer molecule increased when the concentration of manganese carbonyl was raised, but that the branches became shorter.     

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.     

Effect of Hexamethyi Phosphoric Acid Triamide on the Polymerization of Epichlorohydrin-Methyl Methacryiate Initiated with Alkylaluminum

Abstract

The effect of hexamethyi phosphoric acid triamide on the rate of polymerization of AlEt₃-initiated polymerization of epichloro-hydrin and methyl methacryiate was examined. Benzene was used as solvent and the experiments covered AlEt₃ /hexamethyi phosphoric acid triamide ratios from 1:0 to 1:2. Rate of polymerization increased to a maximum at AlEt₃/ hexamethyi phosphoric acid triamide ratio of 1:0.2 and then decreased.

The reaction of hexamethyi phosphoric acid triamide with AlEt, appears to modify the catalytic nature and copolymeriza-tion of epichlorohydrin with methyl methacryiate as demonstrated by enhanced methyl methacryiate reactivity in the presence of hexamethyi phosphoric acid triamide.     

Polymerization of 2-Oxazolines. I. Cationic Polymerization of 2-Phenyl-2-oxazoline Initiated by Various Oxazolinium Salts of Monomer with Brbnsted Acids

Abstract

Various kinds of the complexes of 2-phenyl-2-oxazoline with various Bronsted acids were prepared. From the elementary analysis and spectroscopic analysis of the complex, it was identified to be an equimolar oxazolinium salt. The monomer could be polymerized with the oxazolinium salt to give N-benzoyl-polyethylenimine. The polymer yield in bulk polymerization was linearly proportional to the reaction time, and the number-average degree of polymerization of the polymer obtained at the complete conversion was proportional to the initial molar ratio of the monomer to the complex. The catalytic activities of the oxazolinium salts increased with a decrease in the pK_avalue of Bronsted acid in water. The results of the infrared spectroscopy and nuclear magnetic resonance spectroscopy of the oxazolinium salt at room temperature and elevated temperature indicated that the change of the double bond character of the imino and ether linkages is brought about by the complexation. On the basis of these results, the mechanism of the polymerization was proposed.