Aqueous polymerization of vinyl monomers in the presence of surfactants, 1. Acrylamide

The kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in water were studied in the presence of the anion-active emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polyacrylamide, but it showed no effect on the rate of polymerization. The transfer constants to the emulsifier and the initiator were determined and amounted to of 3,6 · 10^?3 and 5 · 10^?3. The ratio of rate constants of termination and propagation k_t / k_p² = 6,9 · 10^?2 mol · dm^?3 · s, determined for the polymerization of acrylamide in the presence of the emulsifier, is almost identical with the value for the polymerization without emulsifier. Thus, propagation and termination reactions of the potassium peroxodisulfate initiated polymerization of acrylamide in water are not influenced by the emulsifier.     

A kinetic study of the emulsion copolymerization of N,N′-methylenebis(acrylamide) and an unsaturated polyester

The emulsion copolymerization of N,N′-methylenebis(acrylamide) (MBA) and an unsaturated polyester (UP) initiated by potassium peroxodisulfate was kinetically investigated at 50°C by conventional gravimetric and dilatometric methods. The rate of polymerization, the size of latex particles and the number of polymer particles were determined as a function of MBA concentration. The rate of MBA polymerization was found to be proportional to the 0,8th (at 0–15% conversion) and 0,9th (at 20–40% conversion) order with respect to [MBA] at 0,0231 mol · dm^?3 of UP. The values of the reaction order on the monomer concentration are discussed in terms of homogeneous and emulsion polymerization and crosslinking effects. The rate of UP polymerization in the emulsion copolymerization of MBA and UP does not depend on the total monomer concentration. The specific rate of MBA (or UP) polymerization increases with increasing monomer concentration and reaches a maximum at a certain concentration of monomer. The size of polymer particles decreases and the number of particles increases with increasing UP fraction. The stability of polymer particles increases with increasing UP fraction in the monomer feed. The ratio (k_p/k_t^0,5)₀ of the relative rate constants for propagation k_p and termination k_t calculated for the MBA or UP polymerizations at zero conversion increases with increasing MBA concentration. The growth of the polymer particles proceeds via polymerization in particles and by interparticle crosslinking reactions.     

Aqueous polymerization of vinyl monomers in the presence of surfactants, 3. System: Acrylamide/poly(butyl acrylate) latex

The kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in aqueous medium is studied in the presence of poly(butyl acrylate) latex. The rate of acrylamide polymerization increases with the concentration of the latex in the reaction system. The increase is especially pronounced at concentrations of solid latex higher than 100 g per dm³ of polymerization mixture. The activation energy of the acrylamide polymerization in the presence of poly(butyl acrylate) latex is 85,8 kJ · mol^?1. This value is substantially higher than the value of 70,7 kJ · mol^?1 found for the activation energy of the polymerization of acrylamide in the absence of poly(butyl acrylate) latex. A set of reactions is proposed and the equation describing the simultaneous homopolymerization of acrylamide and grafting of poly(butyl acrylate) latex with acrylamide is derived.     

Aqueous polymerization of vinyl monomers in the presence of surfactants, 2. Methacrylamide

The kinetics of the polymerization of methacrylamide initiated by potassium peroxodisulfate in water and 2,2′-azoisobutyronitrile (AIBN) in a water/ethanol mixture (mass ratio 9/1) were studied in the presence of the emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polymethacrylamide, but it showed no effect on the polymerization rate. The transfer constant to the emulsifier determined amounts to 1,8 · 10^?2. The polymerization rate is proportional to the square root of the potassium peroxodisulfate concentration and to the first power of the methacrylamide concentration. During initiation by AIBN, the exponent of the concentration of AIBN in an equation expressing the dependence of the polymerization rate on AIBN concentration amounts to 0,82; the exponent of methacrylamide concentration is equal to 1. The activation energy for the polymerization initiated by K₂S₂O₈ is 67 kJ · mol^?1, whereas for the polymerization initiated by AIBN it is 44,0 kJ · mol^?1.     

Aqueous polymerization of acrylamide initiated by acidic permanganate/thiourea redox system

The polymerization of acrylamide, initiated by acidic permanganate/thiourea redox system, was studied in aqueous media at 30 ± 0,2 °C in nitrogen. The rate of polymerization (R_p) was found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration, within the range of 0,5 · 10^?2 to 1,4 · 10^?2 mol dm^?3, and independent of the thiourea concentration. However, the rate of polymerization varies with the first power of the hydrochloric acid concentration within the range of 2,85 · 10^?2 to 11,4 · 10^?2 mol dm^?3, and increases linearly up to certain extent by varying the monomer concentration from 2,5 · 10^?2 to 12,5 · 10^?2 mol dm^?3. A deviation from the linear behaviour is observed, however, above a concentration of 12,5 · 10^?2 mol dm^?3. The initial rate of polymerization (R_i) as well as the maximum conversion increases by increasing the temperature up to 35 °C, but the maximum conversion falls as the temperature rises above 35 °C. The overall energy of activation is found to be 47,70 kJ mol^?1 (11,48 kcal/mol^?1) within the temperature range of 25–45 °C. Addition of salts, except manganous salts, was found to be associated with a depression in the R_p and maximum conversion. The effect of cationic and anionic surfactants has been found to increase and decrease the R_p respectively; non-ionic detergents, however, have no effect on the R_p.     

The initiation of polymerization of unsaturated tertiary amines with carboxylic acids

The polymerization rate (R_p) of N-methyl-N-phenyl-2-aminoethyl methacrylate (MPAEMA) initiated with 2,2' -azodiisobutyronitrile (AIBN) at 50°C increased considerably after the addition of CCI₃COOH, and distinctly after the addition of CH₃COOH. R_p in a benzene solution of 2 mol. dm^?3 MPAEMA and 5 · 10^?2 mol. dm^?3 CCl₃COOH (without AIBN) was 13% · h^?1. [η] of the obtained polymer corresponded to 64 cm³ · g^?1. The polymerization order of MPAEMA initiated with CCl₃COOH is 0,93 with respect to monomer and 0,51 with respect to CCl₃COOH. The overall activation energy of polymerization of MPAEMA calculated from the temperature dependence of R_p between 20 and 50°C is 43 ± 1,2 kJ · mol^?1. In a benzene solution of 2 mol.dm^?3 MPAEMA, 5 · 10^?2 mol · dm^?3CCl₃COOH and 5 · 10^?3 mol · dm^?3 1,4-benzoquinone at 50°C the polymerization does not proceed for 6 h. In a benzene solution of 2 mol · dm^?3 4-dimethylaminostyrene (4-DMAS) and 2 mol · dm^?3 CH₃COOH (without AIBN), 40% of monomer polymerized within one hour. [η] of the polymer was 4 cm³ · g^?1. The overall activation energy of polymerization of 4-DMAS in the presence of CH₃COOH is ca · 54 kJ · mol^?1. The addition of 5 · 10^?3 1,4-benzoquinone slows down the polymerization rate only slightly. The effect of acids on the elementary polymerization reactions is characterized.     

Preparation of surface-modified polystyrene microspheres by an azo-initiator having analogous structure to the head group of phosphatidylcholine

A novel azo-initiator, 2-[(2-ethylphosphatoethyl)dimethylammonio]ethyl 4,4′-azobis-(4-cyanovalerate) (EAP-501), was prepared. EAP-501 [m. p. 97°C (dec.), λ_max 346 nm in H₂O] was found to be amphiphilic, with a Krafft point of 11,5°C and a critical micelle concentration of 47,2 mmol·dm^?3 at 30°C and 48,6 mmol·dm^?3 at 70°C. The rate and activation parameters for the thermal decomposition of EAP-501 at 70°C were estimated to be k_d = 2,35·10^?5 s^?1, ΔH^≠ = 118,4 kJ·mol^?1 and ΔS^≠ = 10,5 J·mol^?1·K^?1. Emulsion polymerization of styrene initiated with EAP-501 gave polymer microspheres in high yield. The resulting polystyrene microspheres were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The polystyrene microspheres have diameters from 321 to 649 nm by varying the EAP-501 concentration. The ammonium phosphate groups, which are comparable to the polar head group of phospholipids, are concentrated on the surface of the particles. The particles were found to reduce the adsorption of bovine serum albumin (BSA) compared with particles prepared by the emulsion polymerization of styrene initiated with potassium persulfate as an initiator.     

Kinetic and ESR studies of the radical-initiated polymerization of N-(2,6-dimethylphenyl)itaconimide

The polymerization of N-(2,6-dimethylphenyl)itaconimide (1) with azoisobutyronitrile (2) was studied in tetrahydrofuran (THF) kinetically and spectroscopically with the electron spin resonance (ESR) method. The polymerization rate (R_p) at 50°C is given by the equation: R_p = K [2] ^0,5 · [1] ^2,1. The overall activation energy of the polymerization was calculated to be 91 kJ/mol. The number-average molecular weight of poly (1) was in the range of 3500–6500. From an ESR study, the polymerization system was found to involve ESR-observable propagating polymer radicals of 1 under the actual polymerization conditions. Using the polymer radical concentration, the rate constants of propagation (k_p) and termination (k_t) were determined at 50°C. k_p (24–27 L · mol^?1 · s^?1) is almost independent of monomer concentration. On the other hand, k_t (3,8 · 10⁴–2,0 · 10⁵ L · mol^?1 · s^?1) increases with decreasing monomer concentration, which seems mainly responsible for the high dependence of R_p on monomer concentration. Thermogravimetric results showed that thermal degradation of poly (1) occurs rapidly at temperatures higher than 360°C and the residue at 500°C was 12% of the initial polymer. For the copolymerization of 1 (M₁) with styrene (M₂) at 50°C in THF the following copolymerization parameters were found; r₁ = 0,29, r₂ = 0,08, Q₁ = 2,6, and e₁ = +1,1.     

Determination of absolute rate constants for radical polymerization and copolymerization of ethyl α-cyanoacrylate in the presence of effective inhibitors against anionic polymerization

The absolute rate constants of propagation k_p and of termination k_t of ethyl α-cyanoacrylate (ECNA) were determined in bulk at 30°C by means of the rotating sector method under conditions to suppress anionic polymerization; k_p = 1 622 1 · mol^?1 · s^?1 and k_t = 4,11 · 10⁸ 1 · mol^?1 · s^?1 for the polymerization in the presence of acetic acid, and k_p = 1610 1 · mol^?1 · s^?1 and k_t = 4,04 · 10⁸ l · mol^?1 · s^?1 for the polymerization in the presence of 1,3-propanesultone. The magnitude of k/k_t determined was 6,39 · 10^?3 l · mol^?1 · s^?1. The absolute rate constants for cross-propagation in ECNA copolymerizations were also evaluated. Quantitative comparison of the rate constants with those of common monomers and polymer radicals shows that the strong electron-withdrawing power of the ethoxycarbonyl and cyano groups enable the poly(ECNA) radical to add to monomers as fast as the other polymer radicals. The relatively high reactivity of ECNA, regardless of the type of attacking polymer radical, is interpreted by a transition state greatly stabilized by both the ethoxycarbonyl and the cyano groups.     

Terpolymérisation acrylonitrile-styrène-acrylate de méthyle, 4. Copolymérisation en emulsion styrène-acrylate de méthyle en réacteur fermé (batch) en présence de persulfate de potassium

To improve the knowledge of emulsion copolymerization of monomers both swelling their copolymers, but which are of quite different polarity (water solubility), a series of styrene (S)/methyl acrylate (MeA) copolymerizations was carried out in batch at 50°C with potassium persulfate as initiator. The overall rates of copolymerization increase with the amount of MeA in the monomer feed. Copolymer composition follows the usual copolymerization equation if bulk/solution reactivity ratios (r_ij) and monomer partition between aqueous and organic phase are taken into account (simulation). However, accurate kinetic data at low conversion (gas chromatography) put in evidence an enhanced polymerization of the more hydrophilic monomer (MeA), which can be attributed to polymerization in the water phase. Particle sizes increase with conversion and tend to a limiting value, the higher the MeA content is. Particle number (N_p), which is practically constant with conversion of S homopolymerization, tends to increase with MeA content as polymerization proceeds. This trend is enhanced if the emulsifier (sodium dodecanesulfonate, SDS) concentration is increased. Overall propagation rate constants were estimated as function of the experimental conditions and monomer concentration within the particles. From kinetic data (rate of polymerization) and N_p, it was found that the average number of radicals per particle, ñ, remains close to 0,5. It was then possible considering S(k_p = 125 1 · mol^?1 · s^?1) as a standard monomer, to estimate the polymerization rate constant for MeA (335 1 · mol^?1 · s^?1). Since adsorption of emulsifier was shown to be closely related to particle surface composition, the specific area A_s of SDS was measured on latices at various conversions and initial monomer feeds. As conversions increases, the particle surface appears to be richer and richer in MeA, which corresponds to a particle structuration. Strong and weak acid group titration is also in quite good agreement with the colloidal behaviour.     

Untersuchungen zur kationischen polymerisation von oxepan

The ring-opening cationic polymerization of oxepane ( 3 ) was examined in bulk and in solution (1,2-dichloroethane). The initiators used were diethoxycarbenium hexachloroantimonate ( 2 ) and ethylhexamethyleneoxonium hexachloroantimonate ( 4 ). The preparation of 4 is described for the first time. Kinetic experiments showed that the polymerization of 3 is of S_N2-type (analogous to tetrahydrofuran). The propagation rate constants k_p were found to be 1,38·10^?4dm³mol^?1s^?1 at 10°C and 4,38·10^?4dm³mol^?1s^?1 at 20°C. The equilibrium monomer concentrations determined at 0 and 20°C were found to be 0,052 and 0,071 mol dm^?3. Because of the occurence of termination reactions, these equilibrium monomer concentrations, however, were not achieved in all cases. As a possibility for a termination reaction a hydride-abstraction from the monomer is discussed in detail.     

Vinylpolymerisation mit reduzierenden Übergangsmetallverbindungen, 3. Polymerisation in gegenwart von initiatorsystemen aus vanadium(II)- und vanadium (III)-chlorid sowie organischen halogenverbindungen

The polymerization of methyl methacrylate initiated by the redox system vanadium(III) chloride/carbon tetrachloride was studied. The rate of polymerization can be described by the equation R_p = k · [VCl₃]^0,5·[CCl₄]^0,5·[MMA]^1,0. The overall activation energies were estimated to be 74,5 kJ·mol^?1 for VCl₃/CCl₄ and 59,5 kJ·mol^?1 for VCl₂/CCl₄. Vanadium (II) chloride acts as a retarder in the polymerization of styrene initiated by 2,2′-azoisobutyronitrile (AIBN). The polymerization of acrylonitrile and methyl methacrylate is inhibited by vanadium (II) chloride. The polymerization of acrylonitrile initiated by AIBN is retarded by vanadium (III) chloride.     

Free radical polymerization in the presence of non-solvents, 1. Styrene

During styrene (STY) polymerization, initiated by radicals formed by thermal or photochemical decomposition of 2,2′-azoisobutyronitrile (AIBN) the overall polymerization rate constant K defined by relation K = R^p/([AIBN]^0,5 [STY] η) and the ratio k_p/(2k_t0) increase with decreasing styrene concentration by hexane or benzene (R_p is the polymerization rate and η_MIX the viscosity of the reaction system). In the thermally initiated polymerization K = k_p (2f k_d/(2k_t0))^0,5 and in the photochemically initiated polymerization K = k_p (2,303 ? I₀? d/(2k_t0))^0,5 where k_d, k_p, and k_t0 are respectively, the rate constants of AIBN decomposition, of propagation, and of termination (for a system of the viscosity 1 mPa·s) reactions, ? is the quantum yield of radicals entering into reaction with the monomer, I₀ the intensity of the incident light, ? the molar absorption coefficient of AIBN, and d the path length of the light. The increase of K and of k_p/(2k_t0) with decreasing monomer concentration is more marked for the system styrene/hexane than for styrene/benzene and this increase is greater at 30°C than at 60°C. For Θ-systems formed by binary mixtures like styrene/hexane, styrene/decane and styrene/C₁ – C₄ alcohols the values of k_p and k_t0 at 30°C range between 57 and 91 dm³·mol^?1·s^?1 and (0,9 to 2,2)·10⁷ dm³·mPa·mol^?1, i.e. they are in principle identical with the tabulated values of these rate constants for styrene bulk polymerization.     

Role of bulky α-substituent in free-radical polymerization and copolymerization of methyl α-(alkoxymethyl)acrylates

Methyl α-(alkoxymethyl)acrylates were prepared from methyl α-(bromomethyl)acrylate in 80–90% yield. The monomers homopolymerize fast to yield low-molecular-weight polymers. The monomers bearing a linear alkoxymethyl group except for the ethoxymethyl group are characterized by a relatively low ceiling temperature. The rate constants for propagation k_p and termination k_t of methyl α-(butoxymethyl)acrylate were evaluated to be k_p = 298 dm³ · mol^?1 · s^?1 and k_t = 8 · 10⁶ dm³ · mol^?1 · s^?1 at 60°C, respectively. The α-(alkoxymethyl)acrylates are more reactive than methyl methacrylate toward polystyrene radical, except for the α-(dodecyloxymethyl)acrylate which is slightly less reactive, indicating that an increase in the reactivity by the electron-withdrawing character of the alkoxy group prevails over the steric hindrance against addition of the polymer radical, except for the large dodecyloxymethyl group.     

Kinetic and ESR studies on radical polymerization. Radical polymerization behavior of N-octadecylmaleimide in benzene

The polymerization of N-octadecylmaleimide ( 1 ) initiated with azodiisobutyronitrile ( 2 ) was investigated kinetically in benzene. The overall activation energy of the polymerization was calculated to be 94,2 kJ·mol^?1. The polymerization rate (R_p) at 50°C is expressed by the equation, R_p = k[ 2 ]^0,6[ 1 ]^1,7. The homogeneous polymerization system involves ESR-detectable propagating polymer radicals. Using R_p and the polymer radical concentration determined by ESR, the rate constants of propagation (k_p) and termination (k_t) were evaluated at 50°C. k_p (33 L · mol^?1 · s^?1 on the average) is substantially independent of the monomer concentration. On the other hand, k_t (0,3 · 10⁴ – 1,0 · 10⁴ L · mol^?1 · s^?1) is fairly dependent on the monomer concentration, which is ascribable to a high dependence of k_t on the chain length of rigid poly( 1 ). This is the predominant factor for the high order with respect to the monomer concentration in the rate equation. In the copolymerization of 1 (M₁) and St (M₂) with 2 in benzene at 50°C, the following copolymerization parameters were obtained: r₁ = 0,11, r₂ = 0,09, Q₁ = 2,1, and e₁ = +1,4.     

Effect of SnCl4 on the radical-initiated polymerization of diethyl itaconate: Kinetical and ESR studies

The effect of SnCl₄ on the polymerization of diethyl itaconate ( 1 ) with dimethyl 2,2′-azoisobutyrate ( 2 ) in benzene was investigated kinetically and ESR spectroscopically. The polymerization rate (R_p) at 50°C shows a flat maximum on varying the SnCl₄ concentration. The molecular weight of the resulting polymer decreases with increasing SnCl₄ concentration. The overall activation energy of the polymerization is lowered from 52 to 33 kJ · mol^?1 by the presence of SnCl₄, (0,342 mol · L^?1). An NMR study revealed that 1 and SnCl₄ form 1:1 and 2:1 complexes with a large stability constant in benzene. The propagating polymer radicals in the absence and presence of SnCl₄ are ESR-observable as a five-line spectrum under the actual polymerization conditions. The complexed polymer radicals show further three-line splitting due to two methylene hydrogens of the ethyl ester group. The polymer radical concentration increases with the SnCl₄ concentration. The rate constant (k_p) of propagation was determined using R_p and the polymer radical concentration. k_p (6,3–2,9 L · mol^?1 · s^?1 at 50°C) decreases with increasing SnCl₄ concentration. The presence of SnCl₄ (0,342 mol · L^?1) reduces the activation energy of propagation from 29 to 21 kJ · mol^?1. The rate constant (k_t) of termination was estimated from the decay curve of the polymer radicals, k_t (3,1–1,1 · 10⁵ L · mol^?1 s^?1) also decreases with the SnCl₄ concentration. The activation energies of termination in the absence and presence of SnCl₄ (0,342 mol · L^?1) are 30 and 24 kJ · mol^?1, respectively. Suppression of propagation and termination by SnCl₄ seems to be explicable in terms of an entropy factor.     

Rate constants for elementary reactions of the radical polymerization of methyl 2-(benzyloxymethyl)acrylate as polymerizable acrylate bearing large substitutents

Methyl 2-(benzyloxymethyl)acrylate (MBZMA) which was synthesized by reaction of methyl 2-(bromomethyl)acrylate with benzyl alcohol was radically homo- and copolymerized. MBZMA polymerized as fast as methyl methacrylate despite of the presence of a large 2-substituent. The absolute rate constants for propagation and termination were evaluated from the direct determination of the steady state concentration of the propagating radical by electron spin resonance spectroscopy at 60°C: k_p = 182 dm³ · mol^?1 · s^?1 and k_t = 1,6 · 10⁶ dm³ · mol^?1 · s^?1. It was deduced from the magnitude of the rate constants that the balance of the slow propagation and termination allows the formation of a polymer. Evaluation of the cross-propagation rate constants in the copolymerization with styrene revealed that primarily the steric effect of the benzyloxymethyl group reduced the reactivity of the polymer radical and that the electronwithdrawing character of the 2-substituent prevailing the steric effect enhanced the monomer reactivity toward the polystyrene radical.     

Kinetic and ESR studies on radical polymerization. ESR and kinetic evidences for the penultimate effect in the radical-initiated copolymerization of N-cyclohexylmaleimide and bis(2-ethylhexyl) itaconate in benzene

The copolymerization of N-cyclohexylmaleimide ( 1 ) (M₁) and bis(2-ethylhexyl) itaconate ( 2 ) (M₂) with dimethyl 2,2′-azoisobutyrate ( 3 ) as an initiator was carried out at 50°C in benzene. Monomer reactivity ratios were estimated as r₁ = 0,34 and r₂ = 0,38. The copolymerization rate (R_p) and the molecular weight of the resulting copolymer increased with increasing concentration of 1 when the total concentration of comonomers was fixed at 1,00 mol. L^?1. R_p was proportional to [ 3 ]^0,5, indicating a usual bimolecular termination in the copolymerization. An electron spin resonance (ESR) spectrum of the propagating polymer radicals was observable in the actual copolymerization system at 50°C. The spectrum of the copolymerization system is inexplicable in terms of any superposition of spectra observed in the corresponding homopolymerization systems, revealing that some penultimate monomeric unit causes a change in the ESR spectrum, that is, the structure of propagating polymer radical. The apparent rate constant of propagation (k_p) and termination (k_t) were estimated by ESR. The k_p values (1,5–50 L · mol^?1 · s^?1) are fairly higher than those estimated on the basis of the terminal model, affording another piece of evidence for the penultimate effect. The k_t value (1,8–5,4·10³ L · mol^?1 · s^?1) shows a behaviour similar to that of the intrinsic viscosity of the resulting copolymer on varying the monomer feed composition, which seems to reflect diffusion-control of termination reactions.     

Propylene polymerization on titanium-magnesium catalysts determination of the number of active centers and propagation rate constants

By use of the quenching technique with ¹⁴CO and ¹⁴CO₂ the number of active centers and the propagation rate constants (k_p) were determined for the propylene polymerization on different titanium-magnesium catalysts in the presence and absence of an organoaluminium cocatalyst. The k_p values at 70°C were found to be 500–1000 1·mol^?1·s^?1, which were confirmed by independent data of molecular mass measurements of the isotatic polymer after a short polymerization time (5 s). Similar isotactic and atactic k_pvalues were found. The maximum number of active centers for supported titanium-magnesium catalysts can reach about 10% of the titanium content in the catalyst. The k_p values of ethylene polymerization on catalysts active without an organoaluminium cocatalyst were also determined (≈ 10⁴ l·mol^?1·s^?1 at 70°C).     

Styrene polymerization induced by anilino radicals

The polymerization of styrene (St) initiated by 1,4-dimethyl-1,4-diphenyl-2-tetrazene ( 1c ) is studied kinetically in benzene. The polymerization proceeds through a radical mechanism. The rate equation is as follows: R_p = k [ 1c ]^0,5[St]^1,0. The overall activation energy for the polymerization of St is found to be 105,9 kJ · mol^?1. The efficiency of the initiator is also calculated to be 0,67. On the basis of the results, the initiating ability of N-methylanilino radicals is discussed.