Kinetics of anionic polymerization of α-methylstyrene in tetrahydrofuran and toluene mixed solvents

The kinetics of anionic polymerization of α-methylstyrene with Na⁺ as counterion have been studied in mixed solvents of tetrahydrofuran (THF) and toluene in various compositions at ?25 to 5°C. The ion-pair rate constant k(_±) increases by about a factor of 50 at ?10°C, whereas the activation energy decreases from 5.1 to ?2.2 kcal/mole, when THF in the mixed solvent increases from 30 to 100 vol-%. The plot of log k(_±) against (D ? 1)/(2D + 1) is a curve, where D is the dielectric constant of the medium. This deviation from linearity is explained in terms of propagation by two types of ion-pairs.     

Determination of propagation‐rate constant of vinylidene chloride by emulsion polymerization

The propagation‐rate constant of vinylidene chloride (VDC) was determined at 40 and 50 °C, respectively, by applying the so‐called Ugelstad plot to the polymerization‐rate data of the seeded and unseeded emulsion polymerizations of VDC. The values of the propagation‐rate constant k_p thus determined are k_p = 64 dm³/mol · s at 50 °C and k_p = 52 dm³/mol · s at 40 °C, respectively. From these k_p values, the activation energy for propagation reaction was determined to be E_p = 4.2 kcal/mol, which is close to that of vinyl chloride (3.7 kcal/mol). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1005–1015, 2001     

Spatially intermittent polymerization

A novel reactor has been designed which permits the precise determination of absolute rate constants in photoinitiated free-radical vinyl polymerization. A solution of monomer and initiator flows through a dark tubular reactor past regularly spaced slots through which light shines. The alternating dark and light regions produce spatially intermittent polymerization (SIP) and make the system analogous to the well-known rotating-sector technique. However, the SIP reactor has the advantage of producing large volumes of reaction product, at low conversion, suitable for analysis of both conversion and molecular weight. This supplies the necessary data, from a single set of experiments, for the simultaneous determination of the rate constants for propagation and termination. Experimental data are reported at 25°C for methyl methacrylate which indicate that k_p = 315 I./mole-sec, independent of polymer molecular weight, and k_t is dependent on molecular weight especially at low molecular weight, approaching a lower value of k_t = 30 × 10⁶ I./mole-sec at a molecular weight of 10⁶. For styrene, measurements being made only at high molecular weight, k_p = 74 ± 5 and k_t = 37 ± 0.3 × 10⁶ l./mole-sec at 25°C.     

Stereospecific polymerization of isobutyl vinyl ether catalyzed by calcined iron sulfate

The polymerization of isobutyl vinyl ether was studied in a heterogeneous system using iron (II) sulfate calcined in air at various temperatures as a catalyst. The maximum activity was shown by the catalyst calcined at 700°C, which effected the polymerization at room temperature in a few seconds, while the sulfate treated at 750°C was totally inactive. Poly(vinyl ethyl ether) was also obtained by the FeSO₄ (700°C) catalyst at room temperature. This catalyst formed the crystalline polymer (melting temperature 135–138°C) when the reaction was performed in toluene as solvent at room temperature. Poisoning experiments with Hammett indicators were carried out with the FeSO₄ (700°C) catalyst. The treatment with n-butylamine rendered it inactive in the reaction of isobutyl vinyl ether, while its catalytic activity was little affected by dicinnamalacetone. On the basis of the observed results, the nature of active sites of catalyst is discussed.     

Kinetics of the Copolymerization of Methyl Vinyl Ketone and Acrylamide Initiated by the Adduct of Methyl Vinyl Ketone and Imidazole

N-(Butyl-3-one)imidazole acts as an initiating adduct which is formed in the anionic polymerization of methyl vinyl ketone (MVK) induced by imidazole (Im) and is directly formed from Im and the MVK monomer. The kinetics of the anionic homopolymerization of MVK and acrylamide (AAm) under argon in the presence of the adduct were investigated in tetrahydrofuran (THF). The rate of polymerization for the MVK system is expressed as R_p = k[Adduct] [MVK], where k = 3.1 × 10^?6 L/(mol·s)in THF at 30°C. The overall activation energy, E_a , was found to be 5.34 kcal/mol. The R_p for the AAm system is expressed as R_p = k[Adduct] [AAm], where k = 6.8 × 10^?6 L/(mol·s) in THF at 30°C, with E_a 7.78 kcal/mol. The mechanism of the polymerization induced by the initiator adduct is discussed on the basis of these results.     

Studies on polymerization of vinyl acetate using ylide as an initiator and degradative transfer agent

Polymerization of vinyl acetate initiated by β-picolinium p-chlorophenacylide was carried out at 30, 35, and 40°C, using conventional dilatometric technique. The initiator and the monomer exponent values were 0.80 ± 0.15 and unity, respectively. The polymerization was inhibited in the presence of hydroquinone, but was favored by nonpolar solvent and polymerization temperature. The energy of activation was 90.3 KJ mol^?1. An average value of k/k_t for the present system was found to be 0.37 × 10^?2. The results are explained in terms of a radical mode of polymerization with degradative initiator transfer; the principal mode of termination, however, was bimolecular.     

Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. I. THF–CCI4 system

Polymerization of THF in CCl₄ solvent was initiated with 1,3-dioxolan-2-ylium eations with AsF₆^?, PF₆^?, and SbF₆^? anions as well as with esters of fluorosulfonic and trifluoromethanesulfonic acids. With these esters polymerization proceeds with a marked acceleration period, due to slow initiation. The corresponding rate constants of initiation and their dependence on the polarity of the THF/CCl₄ mixture were determined. The rate constant of propagation on the macroion-pairs (k_p^±) of the polytetrahydrofurylium cation with AsF₆^?, PF₆^?, and SbF₆^? and CF₃SO₃^?, anions was found to be independent in CCl₄ solvent on the anion structure and given by the expression: k_p^± = 2.93 × 10^?2 exp {?4.7 × 10³/T} at [THF]₀ = 8.0M. This constant depends on the polarity of the polymerization mixture, and at 25°C for the THF-CCl₄ system, k_p^± = 1.78 × 10^?2 exp {?4.9/D}; thus, in CCl₄ at [THF]₀ = 8.0M, and at 25° k_p^± = 4.0 × 10^?21/mole-sec. In the polymerization with derivatives of CF₃SO₃H (able to form the corresponding macroester) the overall polymerization rate is much lower than that with complex anions because of the reversible conversion of the macroion-pairs into the macroester (internal return). The macroester is much less reactive than the macroionpair (10²–10³ times) in the monomer addition reaction. At [THF]₀ = 8.0M and at 25°C, 96.5% of the growing species exists in the macroester form. Polymerization of THF initiated with derivatives of CF₃SO₃H is a subject of a strong special salt-effect. At a sufficiently high ratio of [AgSbF₆] to [I]₀, where the initiator I is C₂H₅OSO₂CF₃, the overall polymerization rate is equal to that observed for the polymerization of THF on the macroion-pairs, since the internal return within the triflate ion-pair (the macroester formation) is eliminated and polymerization proceeds on the macroion-pairs with SbF₆- anions exclusively.     

Kinetic study on the radical polymerization of 2‐methacryloyloxyethyl phosphorylcholine

Polymerization of 2‐methacryloyloxyethyl phosphorylcholine (MPC) was kinetically investigated in ethanol using dimethyl 2,2′‐azobisisobutyrate (MAIB) as initiator. The overall activation energy of the homogeneous polymerization was calculated to be 71 kJ/mol. The polymerization rate (R_p) was expressed by R_p = k[MAIB]^0.54±0.05 [MPC]^1.8±0.1. The higher dependence of R_p on the monomer concentration comes from acceleration of propagation due to monomer aggregation and also from retardation of termination due to viscosity effect of the MPC monomer. Rate constants of propagation (k_p) and termination (k_t) of MPC were estimated by means of ESR to be k_p = 180 L/mol · s and k_t = 2.8 × 10⁴ L/mol · s at 60 °C, respectively. Because of much slower termination, R_p of MPC in ethanol was found at 60 °C to be 8 times that of methyl methacrylate (MMA) in benzene, though the different solvents were used for MPC and MMA. Polymerization of MPC with MAIB in ethanol was accelerated by the presence of water and retarded by the presence of benzene or acetonitrile. Poly(MPC) showed a peculiar solubility behavior; although poly(MPC) was highly soluble in ethanol and in water, it was insoluble in aqueous ethanol of water content of 7.4–39.8 vol %. The radical copolymerization of MPC (M₁) and styrene (St) (M₂) in ethanol at 50 °C gave the following copolymerization parameters similar to those of the copolymerization of MMA and St; r₁ = 0.39, r₂ = 0.46, Q₁ = 0.76, and e₁ = +0.51. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 509–515, 2000     

Radiation-induced polymerization at high dose rate. I. Isobutyl vinyl ether in bulk

Bulk polymerization of isobutyl vinyl ether was studied at 25°C in a wide dose rate range, 8.2-277 rad/sec by γ rays and 8.8 × 10³-2.2 × 10⁵ rad/sec by electron beams. At low dose rate, 8.2-277 rad/sec, only the radical polymerization took place. At high dose rate exceeding 8.8 × 10³ rad/sec, cationic polymerization was found to occur in addition to the radical polymerization. DP _n of the product at high dose rate was 9-10. Further drying of the monomer increased R_p, and molecular weight of the product formed by cationic mechanism also increased.     

Cationic polymerization behavior of isobutyl vinyl ether with arenesulfonates as non‐salt‐type latent thermal initiators

Substituted and unsubstituted benzenesulfonic acid cyclohexyl esters (1–7) were synthesized, and their possibility as latent thermal initiators in the cationic polymerization of isobutyl vinyl ether (IBVE) was examined to develop novel non‐salt type latent cationic initiators. Thermal decomposition of cyclohexyl p‐nitrobenzenesulfonate (2) in C₆D₆ at 80°C proceeded to exclusively afford cyclohexene as well as p‐nitrobenzenesulfonic acid. Cationic polymerization of IBVE with 1 mol % of an arenesulfonate (1–6) in bulk was carried out at 40–100°C for 12 h. No polymerization took place below 50°C, while the consumption of IBVE depending on both the polymerization temperature and the structure of the arenesulfonates was observed above 60°C. The obtained polyIBVEs showed bimodal GPC curves in several cases, revealing the intervention of two independent propagation species in the polymerization. The cationic polymerization of IBVE with cyclohexyl 2,4,6‐triisopropylbenzenesulfonate (7) at 80°C confirmed the acceleration effect of bulkiness on the polymerization rate. It was concluded that the polymerization was largely dependent on both electronic and steric factors of the aryl groups of the initiators which were directly related to the stability of the sulfonate anions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 293–301, 1999     

Determination of kinetic rate constants in electrochemically initiated anionic polymerization of 1,3-butadiene

The rate constants for electrochemically initiated polymerization were determined by employing a pulsing technique. An electrochemical titration was conducted in which polymer chains were initiated electrochemically, propagated in the absence of current, and terminated electrochemically. The concentrations of supporting electrolyte and monomer were chosen to correspond to those employed in electropolymerization syntheses. The temperature range ?10°C to ?72°C gave k_p = 1.45 × 10² exp {2600/RT}. The Arrhenius parameters are compared to those from previous studies and are interpreted in terms of ion-pair propagation. Precise control of molecular weight distributions is implicit from an accurate knowledge of the kinetic parameters and is reported separately.     

Anionic polymerization of styrene in the presence of different anisoles

The butyllithium-initiated polymerization of styrene has been studied in toluene solution at 20°C in the presence of anisole, o-ethylanisole, and p-ethylanisole. The concentration of styrene was 0.16 mole/1.; the concentration of ether varied from 0.8 to 0.33 mole/1. The rates of initiation were followed spectrophotometrically at γ_max 330 mμ; they increased with increasing concentration of ether. The rates of propagation were measured dilatometrically. In the presence of anisole and p-ethylanisole, the rate expression is R_p = [M][PLi]^1/2(k₁ + k₂ [ether]), where k₁ is the propagation rate constant in pure hydrocarbon, k₂ that of the ether solvated chain end, and [PLi] denotes the concentration of polystyryllithium. On the contrary, o-ethylanisole did not affect the rate of propagation of styrene, possibly on account of the steric hindrance of the o-ethyl group. The apparent first-order termination rate constants were also determined spectrophotometrically at 20°C and compared to those of poly-o- and p-methoxystyryllithium. The following decreasing order of rate constant was found: poly-p-methoxystyryllithium > polystyryllithium-anisole > polystyryllithium–4-ethylanisole > polystyryllithium-2-ethylanisole > poly-o-methoxystyryllithium.     

Effect of the Intramolecular Chain Transfer to Polymer on PLP/SEC Experiments of Alkyl Acrylates

Pulsed‐laser polymerization (PLP) has been adopted by IUPAC as the method of choice for the determination of propagation rate constants (k_p). However, the method has failed in the polymerization of alkyl acrylates at temperatures above 30 °C. In this work, the PLP experiments were analyzed by simulation using a Monte Carlo algorithm. It was found that the experimental difficulties encountered to accurately determine k_p at temperatures above 30 °C were caused by extensive intramolecular chain transfer. This mechanism is not operative at lower temperatures because of its high activation energy.

Pulsed‐laser polymerization of BA in bulk at temperatures between −41 and +40 °C: Simulated MWD trace.     

Kinetics of cationic photopolymerizations of divinyl ethers characterized using in situ Raman spectroscopy

In situ Raman spectroscopy experiments were used to determine effective kinetic propagation constants for a series of unsteady-state divinyl ether polymerizations at different isothermal temperatures and light intensities. Raman spectroscopy was found to be ideally suited for monitoring cationic photopolymerizations because the technique allows isothermal experiments to be performed with excellent time resolution and allows several spectral features to be observed simultaneously. In addition, the Raman experiments provided direct information about the vinyl bond concentration in situ as the reaction takes place. For these cationic photopolymerizations, the reaction rate and limiting conversion were both found to increase as the reaction temperature was increased. At all temperatures, the profile for the propagation rate constant, k_p, exhibited a dramatic increase at the start of the reaction, plateaued at a value between 10 and 40 l/mol s (depending upon temperature), and then decreased as the reaction reached a limiting conversion due to trapping of the active centers. Finally, the overall activation energy for polymerization was found to be 25.1 ± 6.1 kJ/mol. © 1996 John Wiley & Sons, Inc.     

Photoreactions of N-vinylcarbazole induced by metal salts. II. Further studies on the photocationic polymerization sensitized by sodium chloroaurate(III) in nitrobenzene

Further investigations of the photopolymerization of N-vinylcarbazole(VCZ) sensitized by sodium chloroaurate(III) in nitrobenzene were undertaken under irradiation of near-ultraviolet light at 30°C. Copolymerization with isobutyl vinyl ether and the kinetic behavior of polymerization were studied. These propagation and chain-breaking features were discussed in comparison with those obtained in the thermal polymerization. Electron spin resonance spectroscopy was conducted at 77°K in various systems.     

Cationic addition polymerization of 1,4‐dioxene using gacl3 as lewis acid catalyst: Long‐lived species‐mediated polymerization

Effective cationic addition polymerization of 1,4‐dioxene, a six‐membered cyclic olefin with two oxygen atoms adjacent to the double bond, was performed using a simple metal halide catalyst system in dichloromethane. The polymerization was controlled when the reaction was conducted using GaCl₃ in conjunction with an isobutyl vinyl ether–HCl adduct as a cationogen at –78°C to give polymers with predetermined molecular weights and relatively narrow molecular weight distributions. The long‐lived properties of the propagating species were further confirmed by a monomer addition experiment and the analyses of the product polymers by ¹H NMR and MALDI–TOF–MS. Although highly clean propagation proceeded, the apparent rate constant changed during the controlled cationic polymerization of 1,4‐dioxene. The reason for the change was discussed based on polymerization results under various conditions. The obtained poly(1,4‐dioxene) exhibited a very high glass transition temperature (T_g) of 217°C and unique solubility. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Radical polymerization of vinyl thiocyanatoacetate: Participation of group‐transfer mechanism

Vinyl thiocyanatoacetate (VTCA) was synthesized, and its radical polymerization behavior was studied in acetone with dimethyl 2,2′‐azobisisobutyrate (MAIB) as an initiator. The initial polymerization rate (R_p) at 60 °C was expressed by R_p = k[MAIB]^0.6±0.1 [VTCA]^1.0±0.1 where k is a rate constant. The overall activation energy of the polymerization was 112 kJ/mol. The number‐average molecular weights of the resulting poly (VTCA)s (1.4–1.6 × 10⁴) were almost independent of the concentrations of the initiator and monomer, indicating chain transfer to the monomer. The chain‐transfer constant to the monomer was estimated to be 9.6 × 10^?3 at 60 °C. According to the ¹H and ¹³C NMR spectra of poly (VTCA), the radical polymerization of VTCA proceeded through normal vinyl addition and intramolecular transfer of the cyano group. The cyano group transfer became progressively more important with decreasing monomer concentration. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 573–582, 2002; DOI 10.1002/pola.10137     

Kinetic and ESR studies on radical polymerization behavior of N‐(2‐phenylethoxycarbonyl)methacrylamide

Polymerization of N‐(2‐phenylethoxycarbonyl)methacrylamide (PECMA) with dimethyl 2,2′‐azobisisobutyrate (MAIB) was investigated in tetrahydrofuran (THF) kinetically and by means of electron spin resonance (ESR). The overall activation energy of the polymerization was calculated to be 58 kJ/mol. The initial polymerization rate (R_p) is expressed by R_p = k[MAIB]^0.3[PECMA]^2.3 at 60 °C. Such unusual kinetics may be ascribable to primary radical termination and to acceleration of propagation due to monomer association. Propagating poly(PECMA) radical was observed as a 13‐line spectrum by ESR under practical polymerization conditions. ESR‐determined rate constants of propagation (k_p, 4.7–10.5 L/mol s) and termination (k_t, 4.6 × 10⁴ L/ml s) at 60 °C are much lower than those of methacrylamide and methacrylate esters. The Arrhenius plots of k_p and k_t gave activation energies of propagation (24 kJ/mol) and termination (25 kJ/mol). The copolymerizations of PECMA with styrene (St) and acrylonitrile were examined at 60 °C in THF. Copolymerization parameters obtained for the PECMA (M₁) − St(M₂) system are as follows: r₁ = 0.58, r₂ = 0.60, Q₁ = 0.73, and e₁ = +0.22. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4264–4271, 2000     

Radical and cationic polymerizations of 3‐ethyl‐3‐methacryloyloxymethyloxetane

3‐Ethyl‐3‐methacryloyloxymethyloxetane (EMO) was easily polymerized by dimethyl 2,2′‐azobisisobutyrate (MAIB) as the radical initiator through the opening of the vinyl group. The initial polymerization rate (R_p) at 50 °C in benzene was given by R_p = k[MAIB]^0.55 [EMO]^1.2. The overall activation energy of the polymerization was estimated to be 87 kJ/mol. The number‐average molecular weight (M?_n) of the resulting poly(EMO)s was in the range of 1–3.3 × 10⁵. The polymerization system was found to involve electron spin resonance (ESR) observable propagating poly(EMO) radicals under practical polymerization conditions. ESR‐determined rate constants of propagation (k_p) and termination (k_t) at 60 °C are 120 and 2.41 × 10⁵ L/mol s, respectively—much lower than those of the usual methacrylate esters such as methyl methacrylate and glycidyl methacrylate. The radical copolymerization of EMO (M₁) with styrene (M₂) at 60 °C gave the following copolymerization parameters: r₁ = 0.53, r₂ = 0.43, Q₁ = 0.87, and e₁ = +0.42. EMO was also observed to be polymerized by BF₃OEt₂ as the cationic initiator through the opening of the oxetane ring. The M?_n of the resulting polymer was in the range of 650–3100. The cationic polymerization of radically formed poly(EMO) provided a crosslinked polymer showing distinguishably different thermal behaviors from those of the radical and cationic poly(EMO)s. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1269–1279, 2001     

Kinetic studies of the radiation-induced graft polymerization of butadiene onto poly(vinyl chloride) powder

The radiation-induced graft polymerization of butadiene onto poly(vinyl chloride) powder was studied. By the kinetic treatment of elementary reactions the values of k_p and k_t[Z] of the graft polymerization were obtained. The activation energy of the propagation was calculated as 16.0 kcal mole^?1. The value of k_p was proportional of the 0.42 power of the dose rate and that of k_t[Z] was proportional to the 0.84 power of the dose rate.