Homopolymerisation von styrol mit titan(III)-chlorid/alkylhalogenid-initiatoren

The polymerization of styrene initiated by titanium(III) chloride/alkyl halide redox systems was studied. Among the alkyl halides examined, the highest rate of polymerization was found in the system titanium(III) chloride/carbon tetrachloride. The polymerization rate can be described by the equation R_p=k·[Ti(III)]^0,5·[CCl₄]^0,5·[St]^1,0. The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 57,3 kJ/mol. It was found that titanium(III) chloride/chloroacetic acid systems, too, could initiate the polymerization of styrene.     

Functional metal-porphyrazine derivatives and their polymers, 6. Free radical polymerization initiated by Fe(III)-phthalocyanine-2,9,16,23-tetracarboxylic acid

The polymerization of various vinyl compounds initiated by the Mt-phthalocyanine-2,9,16,23-tetracarboxylic acid (Mt-taPc, Mt = Fe(III), Co(II), Ni(II), and Cu(II)) was studied in aprotic polar solvents in the presence and absence of molecular oxygen. Fe(III)-taPc only was found to initiate smoothly the polymerization of methyl methacrylate (MMA) in the presence of air in aprotic polar solvents by a free radical mechanism. The kinetics of the polymerization of MMA initiated by Fe(III)-taPc were studied under air in dimethylformamide at 60°C. The rate of polymerization, R_p, can be expressed as R_p = k[Fe(III)-taPc]^0,5[MMA]^1,5. From the data of electronic and ESR spectra of this polymerization system, the polymerization mechanism is discussed.     

Evaluation of the rate constant for primary radical termination in free radical polymerization

Styrene and methyl methacrylate were polymerized with azodiisobutyronitrile (AIBN) at 50, 60, and 70°C. The average degree of polymerization was kept constant while changing the initiator concentration, by using 1-butanethiol as a chain transfer agent. In these polymerizations, a deviation from the simple kinetic rate law was noticed. This deviation was explained in terms of primary radical termination considering the effect of size dependence of the termination rate constant on the kinetics of free radical polymerization and taking into account the fraction of thermal polymerization. The temperature dependence of the characteristic constant, K_tpr/K_pK_i, was estimated to be 5,408 · 10^?5 exp (12915 cal mol^?1/RT) and 7,52 · 10^?3 exp (7791 cal mol^?1/RT) for styrene/AIBN and methyl methacrylate/AIBN, respectively.     

Functionalized monomers, 2. Kinetics of radical polymerization of oxirane- and oxetane-derivatives of styrene and copolymerization of 4-vinylphenyloxirane with styrene

The kinetics of radical polymerization of 4-vinylphenyloxirane ( 1 ), 4-vinylbenzyloxirane ( 2 ), and 2-(4-vinylphenyl)oxetane ( 3 ) initiated by 2,2′-azoisobutyronitrile (AIBN) was studied. In the case of 1 the initial rate of polymerization was found to depend on the initiator and monomer concentrations as (r_p)_total ∝? [AIBN]^0,5 · [M₁]^1,36. The higher order of the polymerization rate with respect to 1 was interpreted as due to a concurrent thermally initiated polymerization; the rate of the latter was found to depend on the monomer concentration squared. The value of the ratio propagation rate constant over square root of termination rate constant k_p/k_t^1/2 = 2,8 · 10^?2 dm^3/2 · mol^?1/2 · s^?1/2 was determined from the measured dependences (r_p)_total = f[AIBN] and (r_p)_total = f([M₁]), corrected for the rate of thermally initiated polymerization of 1 . On the other hand, the kinetics of radical polymerization of 2 and 3 did not deviate from the standard scheme valid for radical polymerization; in both cases the observed reaction order with respect to initiator and monomer was 0,5 and 1, respectively. Radical copolymerization of 4-vinylphenyloxirane (M₁) with styrene (M₂) was characterized by monomer reactivity ratios r₁ = 1,06 and r₂ = 0,78, respectively, corresponding to the Q, e-scheme values Q = 0,9 and e = ?0,36 for monomer 1 .     

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.     

Über die radikalpolymerisation einiger monomerer in dimethylformamid

The polymerization of acrylonitrile, methyl acrylate, methyl methacrylate, α-chloromethyl acrylate and α-bromo methyl acrylate in dimethylformamide has been investigated using α.α′-azobisisobutyronitrile as initiator. The following relations have been derived at 60°C: for methyl acrylate v = 15.15·10^?4·[I]^0.5·[M], for methyl methacrylate v = 3.46·10^?4·[I]^0.5·[M], for α-chloro methyl acrylate v = 5.25·10^?4·[I]^0.5·[M], and for α-bromo methyl acrylate v = 4.12·10^?4·[I]^0.5·[M]. It has been found that (k_p/k_t^0.5)₆₀ is 14.4·10^?2 for α-chloro methyl acrylate and 12.15·10^?2 for α-bromo methyl acrylate. The relation between the kinetic data obtained and the HAMMETT σ_p constants has been discussed for the substituents in α-position to the double bond which are considered to be the characteristic parameters for the chemical structure of the monomers.     

Vinyl polymerization, 367. Polymerization of methyl methacrylate initiated with sodium polyethylenephosphate in the presence of an aqueous solution of copper(II) chloride

Polymerization of methyl methacrylate (MMA) initiated with the system of sodium polyethylenephosphate (PEP-Na), copper(II) chloride, and water was carried out. The effect of the mass of each component on the conversion of MMA was studied. The polymerization proceeded through a radical mechanism. The overall activation energy was found to be 54,5 kJ·mol^?1. The formation of a complex of Cu(II)-ion with PEP-Na and water was confirmed by electronic absorption spectra. The initiation mechanism was discussed.     

Kinetic study of the polymerization of N,N′-methylenebis(acrylamide) in aqueous dispersion systems

The aqueous-phase polymerization of N,N′-methylenebis(acrylamide) initiated by potassium peroxodisulfate in the absence and in the presence of the anionic emulsifier sodium dodecylsulfate was kinetically investigated at 50°C by conventional gravimetric and dilatometric methods. The rate of polymerization is found to be proportional to the 0,75 and 0,24 oder with respect to potassium peroxodisulfate and N,N′-methylenebis(acrylamide) concentrations, respectively. On the other hand, it is independent of the concentration of sodium dodecylsulfate. This agrees with the polymerization of a monomer soluble in water. Therefore, the equations for a homogeneous polymerization were applied to evaluate the experimental results. The calculated ratio k_p/k_t^0,5 of the rate constants of propagation k_p and termination k_t for the N,N′-methylenebis(acrylamide) polymerization at zero conversion in the absence of emulsifier are scattered in the interval between 3,1 and 3,4 dm^1,5 · mol^?0,5 · s^?0,5 and in the presence of emulsifier in the interval between 2,4 and 3,5 dm^1,5 · mol^?0,5 · s^?0,5. They are close to those obtained for the homogeneous polymerization of acrylamide in the aqueous phase. The lower values of k_p/k_t^0,5 ≈ 0,3–0,6 dm^1,5 · mol^?0,5 · s^?0,5 determined for the polymerization of N,N′-methylenebis(acrylamide) for conversions between 30 and 60% follow from the hindered termination reaction within the polymer particles. The polymer dispersions formed are unstable. The growth of the polymer particles proceeds predominantly by coalescence. This suggests a kinetics which does not follow the Smith-Ewart theory but is characterized by a continuous particle nucleation and agglomeration. The interval 1 occurs at the beginning of the dispersion polymerization when polymer particles are being formed. Interval 2 follows, once the number of polymer particles has been fixed.     

Kinetic studies of the anionic polymerization of methyl methacrylate in tetrahydrofuran with Na+ as counter ion,using monofunctional initiators

A newly designed automatically controlled stirred reactor suitable for kinetic measurements of reactions with half lives ≥2s has been applied to follow the anionic polymerization of methyl methacrylate in THF with Na⁺ as a counter ion in the presence of an excess of NaB(C₆H₅)₄. As initiators were used: benzylsodium reacted with α-methylstyrene (I), fluorenylsodium (II), and 9-methylfluorenylsodium (III). With I the initiation is fast as compared with the polymerization reaction which is first order in monomer concentration. Within the range of ?50°C to ?100°C an almost unperturbed “living” polymerization is observed. The Arrhenius plot of the rate constants results in a straight line with activation energy E_a = 4,4kcal·mol^?1 (= 18kJ·mol^?1) and frequency exponent A = 7,0.II and III are slow initiators, II giving rise to side reactions because of the “acidic” proton in 9-position after initiation, III exhibiting a rate constant of initiation k_i = 1l·mol^?1·s^?1 at ?72°C. The termination reaction is becoming increasingly important with increasing temperature and seems to be a unimolecular reaction with E_a,t = 11,5kcal·mol^?1 (= 48 kJ·mol^?1) and A_t = 10. Since the basic feature of the reactor is the possibility of drawing samples, polymers from each state of the reaction were available to be investigated also with respect to their tacticity. The monomer addition was shown to follow Bernoullian statistics. A structure of the “living” end being in harmony with the results observed is discussed.     

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.     

Interaction of polystyryl radical with copper(II) complexes

The polymerization of styrene initiated by 2,2′-azoisobutyronitrile (AIBN) was studied in N,N-dimethylformamide (DMF) solution at 60°C in the presence of tetrakis(N,N-dimethylformamide)copper(II) perchlorate, and also in the presence of its monoazido copper(II) complex [Cu(DMF)₃N₃]⁺. The monoazido complex in DMF was prepared in situ by mixing solid sodium azide with tetrakis(N,N-dimethylformamide)copper(II) perchlorate in a mole ratio of 1:1. The nature of the complex was established by Job's method. The equilibrium constant K for the reaction [Cu(DMF)₄]²⁺ + N ? [Cu(DMF)₃N₃]⁺ + DMF determined by the limiting logarithmic method was found to be 1,25 · 10⁴l · mol^?1. The presence of [Cu(DMF)₄]²⁺ ions in the polymerization systems caused retardation, but [Cu(DMF)₃N₃]⁺ ions produced well defined induction periods. The rate constants at 60°C for the interaction of polystyryl radical towards [Cu(DMF)₄]²⁺ and [Cu(DMF)₃N₃]⁺ ions were calculated to be 6,6 · 10² and 5,74 · 10⁴ l · mol^?1 · s^?1, respectively.     

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.     

Vinyl polymerization 270. Polymerization of methyl methacrylate initiated by azibenzil

The polymerization of methyl methacrylate initiated by azibenzil (AB) was studied kinetically. The initial rate of polymerization (R_p) was found to be expressed by the equation R_p = k[AB]^0.47[MMA]^0.97. The polymerization proceeded through a radical mechanism. The overall activation energy for the polymerization was estimated as 16.1 kcal/mole. Furthermore, the rate of decomposition of AB was measured in benzene and the following rate equation was obtained: k_d[sec^?1] = 5.75·10¹⁰ exp(-21.9 kcal/RT). From these results the initiation mechanism was discussed.     

The configurational characteristics of conventional poly(methyl methacrylate) in acetonitrile

The θ-temperature and viscosity constant K₀ of radically initiated poly(methyl methacrylate) in acetonitrile were determined from the intrinsic viscosity data (θ = 28°C, K₀ = 4,3 · 10² g^?3/2 · mol^1/2.cm³). The unperturbed coil dimensions are lower in acetonitrile than in other θ-solvents at comparable temperature and indicate a more compact conformation of poly(methyl methacrylate) molecules. The discrepancies in the reported data of the θ and K₀ values are elucidated.     

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.     

Macroion-pairs and macroions in the kinetics of polymerization of hexamethylene oxide (oxepane)

Cationic polymerization of oxepane (hexamethylene oxide) ( 1 ) in CH₂Cl₂ and C₆H₅NO₂ as solvents was initiated with 1,3-dioxolan-2-ylium hexafluoroantimonate ( 2 ). Dissociation constants (K_D) of the ion-pairs of polyoxepane into ions were measured: K_D (in CH₂Cl₂, T = 25°C) = 2,8·10^?5 mol·l^?1 [ΔH_D = ?3,8 kJ·mol^?1 (?0,9 kcal·mol^?1), ΔS_D = ?98 J·mol^?1·K^?1 (?23,4 cal·mol^?1·K^?1)]; K_D (in C₆H₅NO₂, T = 25°C) = 1,6·10^?3 mol·l^?1 [ΔH_D = ?7,1 kJ·mol^?1 (?1,7 kcal·mol^?1), ΔS_D = ?78 J·mol^?1·K^?1 (?18,7 cal·mol^?1·K^?1)]; these values are close to those of the ion-pairs of polytetrahydrofuran. Rate constants k_p⁺ and k_p^±, determined from the kinetic measurements for degrees of dissociation of macroion-paris ranging from 0,02 to 0,21 (in CH₂Cl₂) and from 0,09 to 0,7 (in C₆H₅NO₂), were found to be identical within an experimental error of kinetic measurements. The activation parameters of propagation were measured and their dependences on the polarity of the polymerization mixtures are discussed.     

Polymerizations of 1-(9-anthryl)ethyl methacrylate and charge-transfer complex formations with its polymers

1-(9-Anthryl)ethyl methacrylate (9AEMA) was prepared by condensation of 1-(9-anthryl)ethanol with methacryloyl chloride. The rate of AIBN initiated polymerization of 9AEMA in benzene at 60°C was intermediate between the polymerization rates of styrene and methyl methacrylate. 9AEMA/styrene copolymerization studies at 60°C resulted in the copolymerization parameters r_9AEMA = 0,42±0,07 and r_st = 0,37 ± 0,08. Charge transfer complexes are formed between p- chloranil and the 9AEMA homo- and copolymers. The absorption maxima of the CT-complexes shifted to higher wavelengths with increasing 9AEMA content of the copolymers, whereas the equilibrium constant of the CT-complex formation was independent of copolymer composition. Both the complex formation enthalpies and entropies decreased with increasing 9AEMA content of the copolymers.     

Polymerization of lactams, 92. Non-activated anionic polymerization of ϵ-caprolactam initiated with the sodium salt of ϵ-caprolactam

The non-activated polymerization of ε-caprolactam initiated with the sodium salt of ε-caprolactam (CLNa), which was prepared in situ with sodium methoxide, was studied in the temperature range 170–230°C and at CLNa concentrations from 0.20 to 1.0 mol-%, and at 190°C in the presence of 2.0–10.0 mol-% CLNa. Apparent rate constants and values of apparent activation energy (E_a) were determined for the initial autoaccelerated stage of polymerization (E_a = 230 kJ·mol^–1) as well as for the stage characterized by a zero-order reaction with respect to the monomer (E_a = 120 kJ·mol^–1). Non-integral orders of the polyreaction with respect to the initiator indicate a highly complex polymerization mechanism. Degradation reactions accompany the polymerization at high polymer contents.     

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.     

The polymerization of isobutyl vinyl ether by trifluoroacetic acid

The polymerization of isobutyl vinyl ether (IBVE) initiated by trifluoroacetic acid (TFA) in 1,2-dichloroethane and in 1,2-dichloroethane/carbon tetrachloride mixtures has been studied over the temperature range ?2,5°C to 35°C. Provided that the ratio [IBVE]/[TFA] did not exceed 88 and that 2·10^?4 mol·1^?1 < [TFA] < 4·10^?3 mol·1^?1 polymerization was the only detectable reaction, and the initial rate of reaction R₀ was equal to k[IBVE]²[TFA]. The activation energy of the rate = (34 ± 2) kJ · mol^?1 and the activation energy of the molecular weight = ? (11,9 ± 0,5) kJ · mol^?1. When [TFA] < 1·10^?4 mol/l, no reaction was detectable. The polymers produced had molecular weights less than 4400; the only transfer is by monomer and this is the main chain-breaking step. The reaction was unaffected by the addition of water for [H₂O] < [TFA]. The rate depended on the solvent dielectric constant, but in a manner suggestive of a dipole-dipole reaction. A mechanism is proposed for the reaction in which the reactive intermediates are trifluoroacetate esters solvated by monomer.