Rate Of Monomer Consumption Research Articles

Influence of the nature of cation and anion on the polymerization of tetrahydrofuran initiated by substituted 1,3‐dioxolan‐2‐ylium salts

AbstractTHF polymerization initiated by substituted 1,3‐dioxolan‐2‐ylium salts was investigated. It was found that the rate of monomer consumption depends both on the cation and anion nature. The number, kind and configuration of the substituents of the dioxolenium cations determine their reactivity in the initiation process, hence they influence the catalytic activity of the salts, while the influence of the anion nature on the course of the polymerization is due to the reaction within macroion pairs.

Polymerization of methyl methacrylate initiated by manganese(III) acetate

AbstractThe kinetics of thermal polymerization of methyl methacrylate (MMA) initiated by manganese(III) in sulfuric acid is studied in the temperature range between 40 and 607deg;C. The rate of monomer consumption is found to be dependent on [MMA]2, [H+]−1 but independent of [Mn3+]. The rate of manganic ion consumption is directly proportional to [MMA], [Mn3+] and inversely proportional to [H+]. The chain length is directly proportional to [MMA] and inversely proportional to [Mn3+] and [H+]. A plausible reaction mechanism with initiation by Mn3+ OH− species and termination by the interaction of Mn3+ with the polymer radical is proposed.

Action de différentes especes d'amorçage dans la polymérisation hydrolytique du dodécanelactame‐12

AbstractThe study of the initiation step in the hydrolytic polymerization of 12‐dodecanelactam showed the prominent role of chain‐ends in the monomer consumption and especially that of amino end groups. Different initiators, dodecylamine hydrochloride, 12‐aminododecanoic acid, or lauric acid, where employed and in some experiments water was added. This led to the formation of new end groups and thus to an enhancement of the monomer consumption rate. It could be shown that during this process large changes in the polymer chain length distribution occur.

Cationic polymerization of N-vinyl carbazole by trityl salts—I. : Reactivity of propagating species

The cationic polymerization of N-vinyl carbazole, initiated by Ph 3C + AsF 6 − and Ph 3C + PF 6 − in methylene dichloride at 20 and 0°, has been studied in some detail. Reactions were very fast and rates of monomer consumption were measured using an adiabatic calorimetric technique. Initiation was relatively “slow” but complete, and termination was deduced to be insignificant during kinetic lifetimes. Values for k p were found to vary with the initial initiator concentration; this dependence is discussed in terms of current theories regarding equilibria between ion pairs and free ions in non-aqueous solvents. k p + values estimated from two methods of extrapolation are 9.5 · 10 5 M −1 sec −1 at 20° and 4.8 · 10 5 M −1 sec −1 at 0°. Finally, it has been found that ion pairs are much less reactive than free ions in this system.

Termination and transfer by acids in the pyridine-initiated polymerization of butyl cyanoacrylate

Four strong acids (H 2SO 4, CF 3SO 3H, p-tol · SO 3H, HCl) have been shown to impose identical inhibition periods ( t i) on the polymerization of butyl cyanoacrylate by pyridine in THF at 20°. CF 3COOH causes less sharply defined inhibition and ClCH 2COOH only retardation. The observed t i confirm earlier measurements and the deduced (composite) initiation rate constant for pyridine. Analysis of the rates of monomer consumption during inhibition yields values for the ratios of acid-termination to propagation rate constants, k t/k p, which range 20-fold from H 2SO 4 to CF 3COOH in the above sequence. The effect on the molecular weights is independent of the particular acid, and is interpreted as the consequence of rapid transfer reactions by the terminal acid proton of killed oligomer and polymer molecules.

Investigations on the stereochemistry and polymerization of the 1,3-dioxolane derivatives. VIII

The polymerization of 1,3-dioxolane initiated by a new type of initiator — trisubstituted 1,3-dioxolan-2-ylium salts was studied. It was found that the rate of monomer consumption depends on the kind of substituents and anions as well as on the geometrical structure of the isomeric salt used. The dioxolenium salts with an aliphatic substituent at C-2 and with stable anions are more active then salts with an aromatic substituent or those having unstable anions. In all these cases the cis isomers are more active than respective trans salt isomers.

Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. II. High‐energy electrons irradiation

AbstractVapor‐phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) at high dose rates from an electron accelerator yields the same surface graft structure as does the grafting at low dose rates from 60Co sources; i.e., a homopolymer layer (consisting of only MA component) is easily formed on the inner graft copolymer layer (consisting of both MA and PE components) as a result of the continuously increasing surface graft composition. To produce the surface layer, 4‐MeV electron irradiation with a linear electron accelerator requires only less than 3 min of irradiation time at dose rates of more than 2 Mrad/min, whereas γ irradiation with a 60Co source requires at least 1 hr at dose rates of less than 2 × 103 rad/min. The rate of monomer consumption (or polymerization) in the surface homopolymer layer shows no dependence of irradiation time and a positive dependence of dose rate. It has been suggested that this kinetic feature at the high dose rates shows some contribution of vapor‐phase homopolymerization and subsequent deposition (onto the grafting surface) followed by recombination with the grafted side chain radicals, although secondary graft copolymerization from the grafted chain radicals is still the principal process for the growth of the surface homopolymer layer.

Comparative reactivities of electrogenerated radical cations in cationic polymerization

AbstractPersistent radical cations were produced electrochemically from the parent hydrocarbons 9,10‐diphenylanthracene (DPA), 9‐phenylanthracene (9‐PA), 9,10‐dimethylanthracene (DMA), rubrene (Ru), triphenylene (TP), 1,3,6,8‐tetraphenylpyrene (TPP), and perylene (P). The stabilities of these cations in the absence of monomer were equation image The rates of decay of increased with the dielectric constant of the solvent and were 4 to 5 times greater in CH3CN than in CH2Cl2 or C6H5NO2.The kinetics of the reaction of the radical cation with monomer were investigated for styrene and isobutyl vinyl ether. For styrene and or a first order dependence on the radical cation concentration was found. However, decay was unaffected by the addition of styrene and polymerization was not initiated. With and isobutyl vinyl ether a first order dependence on cation was observed and polymers were obtained.Electropolymerizations were also conducted with the generation of radical cations in situ and the rates of monomer consumption and polymer production were measured. The passage of the same electric charge in Faradays (1 Faraday=96496 coulomb) resulted in the polymerization of different amounts of the monomer and generally paralleled the reactivities found for the various radical cations.

Reactivity and mechanism in the cationic polymerization of p-methoxystyrene initiated by cycloheptatrienyl hexachloroantimonate

The cationic polymerization of p-methoxystyrene initiated by cycloheptatrienyl hexachloroantimonate in dichloromethane solution has been studied in some detail. Reactions proved to be highly exothermic, and rates of monomer consumption were measured using an adiabatic calorimetric technique. Termination was deduced to be insignificant during kinetic lifetimes, and M ̄ n values in the range 10000–50000 showed chain breaking to occur by transfer mechanisms. Appropriate analysis of conversion/time curves allowed computation of enthalpies of polymerization and rate coefficients for propagation, k p (obs), under various conditions. Data for k p (obs) were found to vary with the initial concentrations of initiator and monomer employed, and these dependences are discussed in terms of current theories regarding ion pair/free ion equilibria in nonaqueous solvents. In particular values of 3.6 × 10 3 M −1s −1 and 4.8 × 10 3 M −1s −1 at 0° and +10°C respectively for the rate constant for propagation by free poly ( p-methoxystyryl) cation have been deduced, and a tentative value of 450 M −1s −1 at 0°C has been estimated for the rate constant for propagation by the corresponding hexachloroantimonate ion pairs. These data and the related activation parameters are compared with independent results in the literature. Polymerizations carried out in the presence of excess common ion salt, dimethyl benzyl phenyl ammonium hexachloroantimonate, showed rate depressions far in excess of those predicted by a simple mass law effect, arising possibly as a result of a more dramatic ionic association than simple ion pairing.

Polymerization of 1,2‐butylene oxide initiated by triphenylmethyl salts. I. Kinetics with 1,2‐dichloroethane as solvent

Abstract1,2‐Butylene oxide was polymerized in 1,2‐dichloroethane in the temperature range −20 to + 10°C. Triphenylmethyl salts of hexafluoroantimonate (Ph3CSbF6), hexafluoroarsenate (Ph3CAsF6), and hexafluorophosphate (Ph3CPF6) were employed as initiators. The reactions are characterized by a fast initiation process accompanied by rapid consumption of monomer. This initial stage is followed by a relatively slower polymerization during which the rate of monomer consumption is first‐order in respect to monomer. Variation of the counteranion produces very little influence on the rate. The difference between the thermodynamic parameters found for the first and second stages of the reaction are explained on the basis of two different polymerization mechanisms. The linear dependence of rate on initiator concentration indicates that propagation takes place by ion‐pairs only within the range investigated here.

The polymerisation of styrene on 13X zeolite

AbstractThe polymerisation of styrene on 13X zeolite at 30°C has been studied. Rates of monomer consumption were determined dilatometrically, and the molecular weight distributions of the product were investigated by gel permeation chromatography. The effects of varying the weight of zeolite and the concentration of styrene were studied; the effects of preheating the zeolite samples to two different temperatures were also investigated. A cationic mechanism for the polymerisation is proposed; the initiation is on the zeolite surface and involves adsorbed water. The available space in the vicinity of the sites activated by water appears to determine the rate of propagation, and the molecular weight of the polymer.

Structural Study of the Catalytic Activity of Alkyl Chloride in the Polymerization of N-Phenylethylenimine

Abstract The catalytic activity of various alkyl chlorides in the polymerization of N-phenylethylenimine was studied from the structural point of view. Both the polymerization rate and the molecular weight of the polymer obtained varied with the kind of alkyl chloride. The rate of monomer consumption is expressed by a first-order rate equation with respect to the monomer concentration in the early stage of the polymerization. The efficiency factors of the catalysts differ with the kind of alkyl chloride and increase with an increase in the reaction time. When the chloride of a conjugated alkyl group is used, the polymerization rate decreases with an increase in the ionization potential of the alkyl radical, while it increases when chlorides of a non-conjugated alkyl are used. The structural study of the catalytic activity of the alkyl chloride was made quantitatively from the energetic point of view.

Copolymerization of trioxane with styrene catalyzed by BF3·O(C2H5)2

AbstractIt was determined whether trioxane, a cyclic formal, can copolymerize with styrene, a vinyl monomer, in the presence of BF3·O(C2H5)2 catalyst at 30°C. The methanol‐in‐soluble fraction after extraction with benzene was found to contain the copolymer of styrene and trioxane, thus demonstrating that trioxane can copolymerize with styrene In this case the amount of the methanol‐insoluble polymer was less than that of the total monomer consumed, as determined by gas chromatography. This was found to be caused partly by the formation of the cyclic oligomer, 4‐phenyl‐1,3‐dioxane. The relative reactivity of styrene was qualitatively found to be larger than that of trioxane, not only from the rate of monomer consumption but also from the composition of the methanol‐insoluble polymer obtained. In a nonpolar solvent the reactivity of trioxane increased, and the difference in reactivity between the two monomers decreased. Indeed, an apparent monomer reactivity ratio might be obtained from the relationship between the monomer composition and the monomer consumption rate or the composition of the methanol‐insoluble polymer, but it did not have a quantitative meaning because of the complexity of the copolymerization reaction.

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

AbstractIn 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.

Analysis of Polymerization Kinetics and the Use of a Digital Computer

Abstract The design of chemical reactors for polymerization and degradation processes requires the consideration of the kinetics of reaction systems which may contain several hundred or even thousand consecutive and simultaneous reactions. The problem is further complicated by the fact that the kinetic mechanisms for these processes are not well established. The present paper is a theoretical analysis of addition polymerization, copolymerization and degradation systems occurring in both continuous stirred tank and batch reactors for a number of kinetic models reported in the literature. Analytical solutions are derived for the steady state continuous process. In the batch process a steady state is not assumed and approximately 200 simultaneous first order differential equations for species concentrations are solved numerically. The paper is divided into three parts. Addition polymerization is discussed in the first part for each of the special cases of monomer, spontaneous, combination and disproportionation termination. For the continuous process, the steady state concentrations of the polymers arc obtained and the molecular weight distribution function and the optimum isothermal operating temperature are discussed. For the batch process, the rate equations are solved numerically by the Runge-Kutta method on a digital computer and the effects of the system parameters on the monomer concentration profile and the molecular weight distribution are examined. By the use of numerical methods with a digital computer it is possible to obtain the concentration of each of a large number of polymer species during the course of polymerization. The result of computation shows that the steady state assumption for active polymer species is not accurate, especially in early stage of reaction, and as well, is inaccurate also for high molecular weight active species. In the case of spontaneous termination, the rate of monomer consumption is slower than that in the case of monomer termination, because the monomer is reproduced by the termination process of the active polymer, P1. The profiles of monomer concentration and molecular weight distribution are the same for the cases of no termination and combination termination. Essentially the same treatment is made for copolymerization in the second part. This time the two simultaneous algebraic equations for the monomer concentrations are solved by the Newton-Raphsom method and these are then used to obtain the steady state concentrations of the copolymer species as functions of the system parameters. The analysis of the batch case involves the numerical solution of 194 simultaneous nonlinear first order differential equations. It is shown that the steady state approximation for the active copolymer concentrations cannot be made. There is a little delay in the formation of the dead species relative to that of the corresponding active copolymer. This is expected, because the dead species are produced by the termination reactions of the corresponding active species. In the third part, degradation is considered as random scission, as a chain reaction, and as a reverse polymerization. The rate equations describing the random scission process in a batch reactor arc shown to be linear so that they may be solved by methods of straightforward integration and by matrixes, while the chain reaction and reverse polymerization mechanism require the same numerical techniques as used for polymerization.

Kinetics and chemistry of the polycondensation of esters of ?-amino acids

1. The kinetics of the consumption of glycine ethyl ester during its polycondensation in the presence of carbon dioxide were studied. 2. The first stage of the polycondensation is the formation of carbamate. 3. The rate of monomer consumption does not depend on the method by which the original reaction mixture is formed, i.e. by the addition of carbon dioxide or the immediate introduction of carbamate. 4. A hypothesis is put forward on the autocatalytic nature of the binding of glycine ethyl ester during its polycondensation in the presence of carbon dioxide.

Kinetics of the polymerization of styrene by Friedel-Crafts catalysts.

ALTHOUGH the mechanisms and kinetics of the free-radical catalysed polymerization of styrene have been fairly extensively investigated1,2, the polymerization employing Friedel Crafts catalysts has received much less attention. Williams3 has investigated the stannic chloride catalysed polymerization of styrene in carbon tetrachloride solution and shown that the overall rate of monomer consumption can be represented by the expression: where m is initial styrene concentration, x is styrene consumed in time t, b is initial catalyst concentration. He has also shown that induction periods are present. We are studying the aluminium chloride catalysed polymerization of styrene in carbon tetrachloride solution from a kinetic point of view, and it is proposed to summarize here the principal conclusions reached to date.

Polymerization of olefins and diolefins in suspension and emulsion. Part II

AbstractThis and a previous article (p. 127) review the literature from 1910‐1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acelate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water‐soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat, to the very valuable compilation of patents by Hoseh, and to the enumeration of a selected number of patents in the book of Scheiber.1

Polymerization of olefins and diolefins in suspension and emulsion. Part I.

AbstractThis and a following article review the literature from 1910–1945 on polymerization of olefins and diolefins in suspension and emulsion, and present a number of new measurements not published to date. The subject is considered mainly from the point of view of scientific information on the mechanism of polymerization in aqueous suspensions and emulsions, but brief mention is also made of the more important disclosures in the patent literature. The new data presented in this article refer to (1) initial rates of polymerization of styrene, methyl methacrylate, vinyl acetate and acrylonitrile in aqueous suspensions and in soap emulsions as a function of catalyst concentration, temperature, and soap concentration; (2) influence of water‐soluble activators, such as sodium bisulfite; (3) influence of initial size of monomer droplets on initial rates of monomer consumption; (4) study, with the aid of the electron microscope, of size of monomer droplets and polymer particles throughout polymerization; and (5) a few experiments on side reactions in the domain of higher conversions. No attempt is made in this paper to review and appraise the very large number of recent patents (from about 1930 on), which protect special procedures on the use of various promoting, regulating, or modifying ingredients. A complete digest of this practice does not exist at present, but reference may be made to the excellent chapter on emulsion polymerization in the book of Talalay and Magat (55), to the very valuable compilation of patents by Hosch in “India Rubber World” (27), and to the enumeration of a selected number of patents in the book of Scheiber (50) on pages 210–213.