Bulk polymerization of methyl methacrylate electroinitiated by tetrabutylammonium salts

The radical electroinitiated polymerization of methyl methacrylate has been performed in solutions of tetrabutylammonium salts. TBANO₃ is by far the most efficient, because of the relatively low anodic potential required for the oxidation to the radical. The influence of factors such as temperature, current density, and salt concentration on yields and molecular weights has been examined. The absence of a gel effect allows the onset of a steady state in which the polymerization rate is first-order with respect to monomer.     

Electroinitiated Polymerization of Styrene in a Mixed Two-Phase Medium

In extension of our earlier work on electroinitiated polymerization in biphasic media, the electroinitiated polymerization of styrene has been studied using a mixed two-phase system in which formamide together with some added electrolyte is used as the polar phase and the monomer in the bulk form as the nonpolar phase. Among a series of zinc and ferric salts used as the electrolyte, ZnBr₂ was found to be the most effective. The polymer obtained has a molecular weight of 44–47 ± 10³. The effects of various other parameters, such as the dependence of polymer yield on current, the concentration of the electrolyte, the temperature, and the stirring, have also been examined, and a plausible mechanism based on the electrochemical formation of radicals involving a CT complex has been suggested.     

Electroinitiated polymerization of 1,3-dioxolane in chlorinated hydrocarbons

The electrochemically initiated polymerization of 1,3-dioxolane has been investigated in 1,2-dichloroethane with tetrabutylammonium perchlorate as background electrolyte.The anode process is due to the monomer, and its intermediate oxidation products are probably the initiating species; once initiated, the polymerization reaches an equilibrium which is largely independent of the amount of the initially furnished charge.The conversion at equilibrium on the contrary depends on temperature and initial monomer concentration. The kinetic curves at 50° do not exhibit induction and acceleration periods but autocatalysis becomes important at lower temperature.The polymerization seems slower in dichloromethane, but the process trends to the same equilibrium conversion.The molecular weight of the polymers depends on temperature, monomer concentration and amount of initiating charge: apart from some chain transfer acting in the first stage of polymerization, the process exhibits “living” features in the increase of molecular weight with conversion.     

Electrochemical bulk polymerization of methyl methacrylate in the presence of nitric acid

The electroinitiated polymerization of methyl methacrylate in the presence of nitric acid has been investigated on platinum and graphite anodes. The dependence of yields and molecular weights on parameters such as current density, temperature, speed of stirring, and HNO₃ concentration was determined. Under continuous electrolysis conditions a stationary state takes place and the rate of polymerization exhibits zero order with respect to monomer and a 1.5 order with respect to current. On the other hand, under postpolymerization conditions a kinetic gel effect occurs, which limits the termination rate and leads to the typical acceleration in the conversion–time curves. The effect of postpolymerization is so marked, even after supplying small amounts of charge, that the formation of long-lived radical chains is believed to be possible. In this respect HNO₃ would play a fundamental role by stabilizing the growing radicals.     

Electroinitiated polymerization of acrylamide in acetonitrile medium

The electroinitiated polymerization of acrylamide (AA) has been studied in acetonitrile medium using tetrabutylammonium perchlorate (TBAP) as the electrolyte. Split-cell experiments showed that the polymer formation takes place both in the anode and the cathode compartments. The polymer yield depends on several factors such as the magnitude of the current flow, the duration of the electrolysis, the monomer concentration, the electrolyte concentration, the temperature of the solution, presence or absence of air, and finally whether or not the cell content was stirred. The current exponent of the polymerization was 0.28 with a reaction rate constant of 1.06 reaction % per hour. The IR and NMR spectra of the polymers suggest that the anodic polymer is polyacrylamide and the cathodic polymer is poly-β-alanine (? CH₂? CH₂? CO? NH? ). Based on the experimental results, a radical mechanism for the anodic polymerization and an anionic mechanism for the cathodic polymerization have been proposed.     

Electroinitiated cationic polymerization of styrene in the presence of ferric chloride

The electroinitiated polymerization of styrene has been studied in acetone with ferric chloride as the electrolyte. At a fixed monomer concentration, the polymer yield depends on the current strength as well as the concentration of ferric chloride. The molecular weight of the polymer lies in the range of 1000–3000. Addition of zinc chloride to the system or replacement of the solvent by DMF (partly or fully) or methanol retards the polymerization. The current exponent of polymerization is unity with a reaction rate constant of 4.416 × 10^?2 reaction percent per hour. The locus of polymerization is the anode compartment. A cationic mechanism has been proposed for the polymerization, the initiating step consisting of an electron transfer from an adsorbed charge transfer complex of styrene and ferric chloride.     

Electroinitiated polymerization of allylphenylether

Electroinitiated polymerization of allylphenylether via constant potential electrolysis was accomplished in acetonitrile at room temperature. Electroinitiated polymerization of the monomer yielded insoluble polymers on the surface of the anode together with soluble polymers in the bulk solution. The structural analyses of the polymers were done by ¹H-NMR and FTIR spectroscopy. ¹H-NMR results showed that monosubstituted aromatic ring of the monomer becomes tri-substituted during the electroinitiated polymerization. The effect of monomer concentration and applied potential on the rate of electroinitiated polymerization were also studied. © 1995 John Wiley & Sons, Inc.     

Cationic polymerization of styrene with electrochemically generated perchloric acid—I

The electroinitiated polymerization of styrene in LiClO₄-propylene carbonate solutions leads to polystyrene at the anode through the formation of HClO₄. The influences on this polymerization of factors such as temperature, current, monomer and electrolyte concentrations, and dielectric constant of the medium, have been examined. The trends of the yields as functions of these factors show some anomalies. In particular, there is a maximum in the yield vs current curve. The molecular weights are relatively low, due to transfer processes, both spontaneous and involving monomer. The propagation proceeds by a cationic mechanism, in which free ions are in equilibrium with ion pairs.     

Copolymerization of styrene and diethyl fumarate with zinc bromide. III. Electroinitiation at low current densities

The electroinitiated preparation of equimolar copolymers of styrene and diethyl fumarate is described. The reaction medium consisted of these monomers dissolved in a methanol–zinc bromide solution. Rates of polymerization increased with increasing applied current and the copolymer yield increased linearly with the total number of Faradays transferred. The copolymer composition is 1:1 and is essentially invariant with the degree of conversion (<15%), electroinitiation rate, and monomer feed ratios. A reaction mechanism involving donor–acceptor complexes and electroinitiated excitation of these complexes at the electrode is postulated.     

Changes in concentration of tetraoxane produced during the solution polymerization of trioxane catalyzed by BF3·O(C2H5)2

The behavior of tetraoxane produced during the polymerization of trioxane was investigated kinetically. In the polymerization of trioxane, a short induction period for the formation of methanol-insoluble polymer was observed and during the induction period a certain amount of tetraoxane, depending on the polymerization conditions, was produced. This amount was independent of the initial concentration of catalyst but increased with an increase in the polymerization temperature and in the initial concentration of trioxane. So this amount was found to be determined by the equilibrium between the formation and consumption of tetraoxane. On the other hand, in the early stage of polymerization of trioxane, the formation of an appreciable amount of soluble polymer was estimated. Consequently the formation of tetraoxane was explained in terms of the “back-biting” reaction of the soluble growing chain with depolymerization.     

Electroinitiated Polymerization of Acrolein by Direct and Indirect Electron Transfer Via Controlled Potential Electrolysis

Electroinitiated polymerization of acrolein has been achieved by controlled potential electrolysis at the reduction peak potential of the monomer for direct electron transfer. Kinetics and type of mechanism of the polymerization have been investigated. the structure of the polymer has also been examined by IR spectroscopy. in a separate experiment, a small amount of CCI₄ was added to a polymerization system. Since the reduction peak potential of CCI₄ appears at a more anodic region than that of acrolein on mercurized platinum, initiation proceeds via the electrolytic product of CCI₄. the direct and indirect initiation mechanisms are compared. It is found that electroinitiated polymerization of acrolein carried out by direct electron transfer from cathode to monomer (in the absence of CCI₄) proceeds simultaneously via radical and anionic mechanism.     

Electroinitiated polymerization of acrylonitrile in aqueous sulphuric acid

The electroinitiated polymerization of acrylonitrile in aqueous sulphuric acid has been investigated. The polymerization, which occurs at the anode through the formation of radicals from HSO₄^?, is heterogeneous in nature and shows the occurrence of occlusion phenomena. A remarkable after-effect, connected with the occlusion of free radicals, was observed. Chain transfer to monomer, solvent and polymer have sufficiently low values to allow the formation of a polymer with high molecular weight.     

Electroinitiated polymerization of styrene in dimethylsulphate

The electroinitiated polymerization of styrene in tetrabutylammonium perchlorate-dimethylsulphate solutions has been investigated. Polystyrene of low molecular weight is formed cationically through a direct monomer oxidation to the radical cation. Kinetic as well as mechanistic considerations for this system are made difficult by a number of factors: (a) the polymer is to a large extent insoluble in dimethylsulphate; (b) side reactions of both monomer and polymer tend to decrease the yields and therefore the calculated k_p values: (c) the supporting electrolyte concentration tends to affect the ionic equilibria in solution, so again influencing the k_p values.

A polymer degradation, found for polystyrene in LiClO₄-propylene carbonate solutions, was again noted and attributed to the effect of the current on the polymer covering the anode. The polymerization has no true termination, the only chain-stopping reactions being those giving rise to chain transfer.     

Electro-initiated cationic polymerizations—V. Polymerization of cyclohexylvinylether in the presence of tetrabutylammonium salts

The electrochemical polymerization of cyclohexylvinylether has been investigated in 1.2-dichloroethane solution using various tetrabutylammonium salts, viz. tri-iodide, iodide, tetrafluoroborate and perchlorate, as supporting electrolytes in reaction cells with two platinum electrodes. The first two salts were unsuitable for an electrochemical polymerization; in the presence of tetrafluoroborate or perchlorate, pulses of constant current induce an anodic polymerization for which the electrochemical and kinetic characteristics have been examined. Initiation is attributed to electrochemically formed protons but their source seems different from that generally reported. Anodic polarography and potentiostatic electrolyses of the electrolyte solutions have excluded the oxidation both of the solvent and the supporting salt, besides that of the monomer. Hence, it is likely that the initiating protons arise from the electrochemical oxidation of residual water.     

An electrochemical route to phenol–formaldehyde precursors

With the aid of VPC and NMR, the electroinitiated polymerization of phenol or p-tert-butyl phenol with formaldehyde in the presence of basic electrolytes has been investigated over a range of current densities. Results from an electroinitiation study were contrasted with base-catalyzed thermal polymerizations and, except for yield, found to be essentially invariant. GPC of the electroinitiated and thermally polymerized resins indicates similar results with low molecular weight species of relatively narrow molecular weight distribution being the principal products. An electroinitiation mechanism, in agreement with the mechanism for base-catalyzed thermal polymerization is proposed to describe these experimental results.     

Electroinitiated polymerization of arylvinyl monomers

The electroinitiated polymerizations of styrene, 2-vinylnaphthalene, and 9-vinylanthracene were compared in sulfolane and acetone solvents in the presence of ZnCl₂. The relative orders of polymerization rates and polymerization efficiencies, in both solvents, were 9-vinylanthracene > 2-vinylnaphthalene > styrene, with faster rates and higher efficiencies occurring in sulfolane. Data obtained from viscosity and gel permeation chromatography (GPC) studies indicate that the molecular weights of the polymers produced in these systems are extremely low, <5000. Chemical composition and infrared (IR) spectral data suggest that abnormal transfer reactions (possibly from solvent) may be occurring in the electroinitiated 9-vinylanthracene polymerizations. The polymerization mechanism appears to be cationic in these monomer–solvent systems with ZnCl₂.     

Cationic polymerization of styrene with electrochemically generated perchloric acid—II

The electroinitiated polymerization of styrene in LiClO₄-PC solutions has a living character due to the absence of termination. Marked side reactions were observed, limiting the yields. These reactions are mainly due to monomer oxidation by HClO₄ and polymer degradation at the anode. They can be minimized by increasing the monomer concentration. Conversion vs time curves show an induction period, an ascending linear portion and a descending portion. Kinetic treatment limited to the ascending portions shows that the polymerization is first-order with respect to monomer and HClO₄ concentrations. K_p values are considerably lower than those found in HClO₄C₂H₄Cl₂ and in HClO₄CH₂Cl₂, thus confirming that the influence of the solvent in these processes is not merely electrostatic.     

Rates of polymer formation and monomer consumption in the solution polymerization of trioxane catalyzed by BF3 · O(C2H5)2

In the solution polymerization of trioxane catalyzed by BF₃ · O(C₂H₅)₂ at 30°C. the amount of the methanol-insoluble polyoxymethylene is less than the amount of monomer consumed. This difference was much larger than the amount of formaldehyde determined in the polymerized system and could not also be explained in terms of the amount of the methanol-soluble oligomer. Tetraoxane was detected in large quantities by gas chromatography in the polymerized solution of trioxane. Therefore, the difference between the amounts of the methanol-insoluble polymer and the monomer consumed was ascribed partly to the formation of tetraoxane. In spite of the fact that tetraoxane was polymerized more easily than trioxane by BF₃ · O(C₂H₅)₂, an almost constant amount of tetraoxane was produced, independent of the kind of solvent and the polymer yield. This suggests the existence of an equilibrium concentration of tetraoxane. On the other hand, the formation of trioxane was observed in the solution polymerization of tetraoxane by BF₃ · O(C₂H₅)₂. This suggests that the formation of tetraoxane during the trioxane polymerization is due to a back-biting reaction in which the growing chain end of trioxane attacks the oxygen atom in its own chain with depolymerization of tetraoxane.     

Polymerization of Trioxane

A survey of the possible modes of polymerization of trioxane is followed by a discussion of current ideas concerning the course of the polymerization. The polymerization, which involves ring cleavage, is characterized by a number of side reactions of the growing polyoxymethylene cations, such as chain transfer, transacetalization, and hydride shift. These reactions not only determine the nature of the end groups and the molecular weight of the resulting polyoxymethylenes, but are also responsible for their chemical and molecular uniformity. Special emphasis is placed on the role of the monomeric formaldehyde formed during the polymerization of trioxane.     

Dicyclopentadiene Polymerization in Solutions under the Action of Various Catalytic Systems

The kinetics of dicyclopentadiene polymerization in toluene solution under the action of different catalytic systems through adiabatic thermometry was investigated. Unlike cationic metathesis polymerization has a sufficiently large induction period associated with low speed by implantation monomer on carbine bond of catalyst. It has been shown that the rate of metathesis polymerization of dicyclopentadiene in comparable circumstances is about three times lower than the rate of cationic polymerization of the same monomer.