Activation Energy Of Polymerization Research Articles

Use of electrical conductivity for studying the kinetics of formation of poly-amino-bis-maleimides

The electrical conductivity method has been used to study some aspects of the kinetics of polymerization in the melt of thermosetting polyimides-poly-amino-bis-maleimides based on aromatic diamines. A characteristic feature of the formation of the polymer from the melt of all poly-amino-bis-maleimides is the two-stage nature of the process. The temperature intervals of the course of the first and second stages of the process of curing and structuring in the material are defined. The nominal rate constants of polymerization have been calculated and the effective values of the activation energies of polymerization found.

Nitric oxide initiated polymerization of acrylonitrile

AbstractNitric oxide initiated polymerization of acrylonitrile in dimethylsulfoxide was carried out. The dependence of monomer and initiator concentrations and temperature on polymer yield and initial rate of polymerization (Rin) was studied. The over‐all activation energy of polymerization was found to be about 19.96 kcal · mol−1 (83.43 kJ · mol−1). The polymerization of acrylonitrile appears to occur via free radical mechanism. A kinetic scheme and rate expression have been proposed.

Study on the preirradiation polymerization of vinyl monomers

This paper presents mainly the polymerization, copolymerization and crosslinking of monomers off-source induced by peroxides which are formed by high energy irradiation of vinyl monomers such as styrene (St), acrylonitrile (AN), methylmethacrylate (MMA), vinyl acetate (VAc) and 2-hydroxyethyl methacrylate (HEMA). The peroxides produced by irradiation of the above-mentioned monomers can not only induce the monomers themselves, but also another non-irradiated monomer to carry out copolymerization efficiently. The activation energy of peroxide formation, the apparent activation energy of polymerization and the activation energy of peroxide initiation by irradiation of vinyl monomers are: E f(MMA) = 11, E f(St) = 9.6, E f(AN) = 8.5, E MMA = E VA = 11.4, E i(MMA) = E i(VA) = 13 kcal/mol. The rate of decomposition of monomer peroxides is smoother than that of BPO during the polymerization and so a smooth kinetic progress is obtained. The initiating ability of forming peroxides by irradiation of the vinyl monomers depends mainly on the chemical structure of the monomers. For instance, the main structure of peroxides formed during preirradiation MMA are: alternating peroxy-copolymer ▪ and random peroxy-copolymer ▪ Owing to the peroxy-bond which is unstable and in which homolytic breakage easily occurs to yield a pair of radicals, RO . is formed within the above-mentioned structural compounds, so that they possess stronger initiating reactivity. It is quite evident that the initiating reactivity of AN peroxide will be greatly reduced because of the conjugate double bond. In other words, the initiating ability of AN peroxide is lower than MMA peroxide and St peroxide.

Silica-supported chromium catalysts for ethylene polymerization: The active oxidation states of chromium

The reduction of Cr(III) SiO 2 to Cr(II) SiO 2 with CO led to a change in the kinetically significant site for the polymerization of ethylene at low temperatures and pressures. Cr(III) SiO 2 displayed higher activity than Cr(II) SiO 2 over the same range of reaction temperatures. Cr(II) SiO 2 catalysts were characterized by a sharp falloff in polymerization activity at temperatures <40 °C. Activation energies for polymerization over Cr(III) SiO 2 and Cr(II) SiO 2 were 10.6 and 17.1 kcal mole −1, respectively. Hydrogen sulfide poisoning of Cr(III) SiO 2 and Cr(II) SiO 2 indicated that the active fraction of Cr was 13 and 34% of the total chromium, respectively. Infrared spectra of adsorbed CO and NO suggest that the active sites on Cr(II) catalysts are C-type Cr(II) ions with at least two vacant coordination positions available for the growing polymer chain and the monomer. Thermal activation of Cr(II) SiO 2 catalysts at 700 °C ( in vacuo) resulted in both an increase in the concentration of C-type Cr(II) ions and polymerization activity. A decrease in the activation energy of ethylene polymerization for Cr(II) SiO 2(700) and a blue shift in the infrared band associated with the nitrosyl complex of this species suggest that the thermal treatment modified the surface coordination of these ions. Most importantly, thermal activation of Cr(II) SiO 2 produced a Cr(II) catalyst which is active for ethylene polymerization at 25 °C.

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

AbstractThe 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.

Application of the Spin Trapping Technique to Radical Polymerization. 21. Vinyl Polymerization with the N-Hydroxysuccinimide/Acetylacetonato Metal Chelate System

Abstract Some combinations of N-hydroxysuccinimide (NHS) and acetyl-acetonato metal chelates were found to induce radical polymerization. A kinetic study on the polymerization of methyl methacrylate (MMA) was performed by using as initiator the NHS/trisacetyl-acetonatomanganese(III) (Mn(acac)3) system, which can initiate the polymerization effectively even at room temperature. The overall activation energy of polymerization was very low (9.1 kcal/mol). The polymerization rate (Rp) was expressed by where the initiator concentration was varied by fixing [NHS]/[Mn(acac)3] = 2. Rp showed a maximum when [Mn(acac)3] was changed while keeping [NHS] constant. Further, a spin trapping study revealed that the primary propagating radical was trapped even in the system containing only a small amount of monomer (1.6 × 10−2 mol/L). These results indicate that a complex from NHS and Mn(acac)3 with a very high stability constant plays an important role in the generation of initiating radicals, and that the monomer partic...

Mechanism of N‐vinylcarbazole polymerization on Co(II)–13X molecular sieve

AbstractKinetics of polymerization of N‐vinylcarbazole over Co(II)‐13X molecular sieves in toluene have been studied. The rate of polymerization (Rp) has been found to be second order with respect to percent exchange level of Co(II) and also to the NVC concentration at all the reaction temperatures of 40, 50 and 60°C. The rate increases with decreasing pH of the original exchanging salt solution up to a pH of about 3.5, beyond which it falls. The overall activation energy of polymerization has been found to decrease with increase in monomer concentration, exchange level of Co(II), and the hydrogen ion concentration of the original exchange solution. Average degree of polymerization also follows a similar trend. A mechanism of polymerization involving simultaneous propagation on both metal ion Co(II) and proton on a zeolite surface has been suggested. The two propagation routes are characterized by an average activation energy of 10.36 kcal/mol and 5.40 kcal/mol on the metal ion and proton centers, respectively.

No2–initiated polymerization of acrylamide in dimethylsulfoxide

AbstractNO2‐initiated polymerization of acrylamide in dimethylsulfoxide was carried out. The dependence of monomer, initiator concentrations, and temperature on polymer yield and initial rate of polymerization was studied. The overall activation energy of polymerization was calculated to be about 15 kcal mol−1. The copolymerization of acrylamide with methyl methacrylate was also studied. The kinetic mechanism of polymerization was proposed.

Free-Radical Polymerization of Acrylic Acid in Benzene

Abstract The polymerization of acrylic acid with NO2 in benzene was carried out. The initial rate of polymerization shows first-order dependence on the monomer concentration and half-power dependence on the initiator concentration. The molecular weight of polymers also shows dependence on monomer and initiator concentrations. The overall activation energy of polymerization was found to be about 22.7 kcal/mol. The kinetic mechanism of polymerization is discussed.

Core‐shell emulsion copolymerization of styrene and acrylonitrile on polystyrene seed particles

AbstractSeeded emulsion copolymerization of an azeotropic composition of styrene (St) and an acrylinitrile (AN) comonomer mixture in polystyrene (PS) seed at different polymerization temperature of 55–75°C were investigated. The kinetic data showed a transition temperature at 65°C, above which the activation energy of polymerization is low, 6.1 Kcal/mol, compared with 9.8 Kcal/mol below it. The particle‐size results and thin layer chromatographic (TLC) data showed two types of particle of different composition and morphology in the final latex system: a smaller size of (St–AN) copolymer and a larger size of core‐PS and (St–AN) copolymer shell, with a zone of PS grafted (St–AN) copolymer in between. Various polymerization parameters, that is emulsifier concentration, type of seed particle and its size, and monomer/polymer ratio, were studied and their effects on particle size and particle morphology were examined. The percent of grafted core‐PS was 10% below a polymerization temperature of 65°C and 40% above that temperature. By adjusting the size and number of the seed particles, monomer‐polymer ratio, and emulsifier concentration conditions were established in which a final copolymer latex with “perfect” core‐shell morphology was achieved.

Kinetics of the polymerization of styrene with butoxytitanium trichloride and trialkylaluminium

AbstractThe kinetics of polymerization of styrene in heptane was investigated using butoxytitanium trichloride and triethylaluminium/triisobutylaluminium as cocatalysts. A steady state polymerization after an initial period of declining rates lasting for 20 – 60 min was observed. Both the catalysts systems polymerize styrene at a slow rate ( ≈ 10−6 mol · dm−3 · s−1). The steady state rates show a maximum at an [A1] : [Ti] ratio of 1,5 and exhibit a first‐order rate law with reference to both the monomer and the catalyst. Addition of triethylamine, an electron donor, greatly influences the rates of polymerization when triethylaluminium is used, whereas in the case of triisobutylaluminium, the rates are not greatly influenced by the presence or absence of triethylamine. The effect of the electron donor on the rates of polymerization can be explained by the competitive complexation of the alkylaluminium and the electron donor at the active site. The overall activation energy of polymerization (44 – 46 kJ · mol−1) is in accord with a coordinated anionic mechanism. An alkylated alkoxytitanium halide species as the chemical entity affecting polymerization is suggested.

Synthesis and polymerization of water‐soluble polydiacetylenes

AbstractSynthesis of two classes of water‐soluble polydiacetylenes °CR—CC—CRx is presented. Class I has carboxylic acid [R = —(CH2)nCOOH] and their salts as the side group, while the class II has urethane–carboxylic acid [R = —(CH2)nOCONHCH2COOH] and their salts as the side group. Monomers of class I were prepared by oxidation of diacetylenes having R = —(CH2)n+1OH group, while those of class II were prepared by hydrolysis of diacetylenes having R = —(CH2)nOCONHCH2COO(CH2)nCH3 group. The monomers polymerize in the solid state either upon thermal annealing or upon exposure to high‐energy radiation. 1HAU, R = —CH2OCONHCH2COOH, polymerizes quantitatively upon thermal annealing. The heat of polymerization (130 kJ/mol) and the activation energy of polymerization (110 kJ/mol) as determined by differential scanning calorimetry are in agreement with those reported for other diacetylenes.

Polymerization of acrylic monomers in presence of sulphuric acid

The effect of sulphuric acid on the polymerization of methylacrylate and butylacrylate has been studied. It is shown that the dependence of the rate of polymerization on the concentration of acid passes through a maximum. The authors established the formation of sulphuric acid complexes with acrylic monomers the composition of which depends on the ratio of concentrations of the components in the solution. In presence of the acid the ratio k p /k 0 1 2 rises, the rate of initiation and the M of the polymer formed rise with acceleration of the degradation of the polymer peroxides and decrease in the effective activation energy of polymerization.

Low temperature radiation induced polymerization of triethylene glycol α,ω-dimethacrylate

A calorimetric study has been made of the post-radiation polymerization of triethylene glycol,α, ω-dimethacrylate. The low temperature radiolysis has been investigated by ESR. The radiation yield of radicals was found to be 6 ± 1 1/100 eV. Transformation of the radicals spectrum into the spectrum of propagating macroradicals takes place at 140 K. An intensive postpolymerization process follows transition from the glassy to the liquid state ( T g = 193). Radical decay is observed during polymerization. For the low temperature region a value of E eff = 50·7 ± 0·8 kJ/mole was obtained for the effectve activation energy of polymerization.

Polymerization of lactams, 64. Nonactivated anionic polymerization of 2‐pyrrolidone in the presence of quaternary ammonium cations

AbstractThe effect of addition of quaternary ammonium halides was studied in the nonactivated polymerization of 2‐pyrrolidone (1) initiated with the potassium salt of 2‐pyrrolidone (2‐oxo‐1‐pyrrolidinylpotassium) (2). The polymerization was accelerated upon small additions of Me4NCl, whereas addition of Et4NBr and Bu4NBr rather had a retardation effect and reduced the molecular weight of polymer. The formation of the corresponding quaternary ammonium salts of 2‐pyrrolidone in situ is analogous to the formation of the pure salts in their synthesis from the ammonium halides. The nonactivated polymerization of 1 initiated with the pure tetramethylammonium salt of 2‐pyrrolidone (3) showed all kinetic features of other nonactivated polymerizations of 1. High yields and molecular weights of poly(2‐pyrrolidone) and a higher number of growth centers during polymerization are evidence of a higher dissociation of 3 dissolved in 1 in comparison with 2 as the initiator. The activation energy of polymerization activated with 3 (47,9 kJ · mol−1 in the range 35 to 55°C) and the reaction order with respect to 3 (1,3 at 45°C) were determined.

Kinetics of the nitrogen dioxide initiated polymerization of acrylic acid

AbstractAcrylic acid (AA) was polymerized with NO2 in tetrahydrofuran (THF) and in 1,4‐dioxane. The effects of monomer and initiator concentration and of temperature on polymer conversion, initial rate of polymerization, and molecular weight were studied. The overall activation energy of polymerization was found to be 16,3 kcal mol−1 (68,23 kJ · mol−1) and 15,54 kcal · mol−1 (65,05 kJ · mol−1) in THF and in 1,4‐dioxane, respectively. High molecular weight polymers (M ca. 105) were obtained. The polymerization appears to be initiated by free radicals.

Mechanism of styrene emulsion polymerization during interval II

AbstractA systematic study of the kinetics of styrene emulsion polymerization in the postnucleation stage by the way of seed particle growth of monodisperse latices was undertaken, in which the colloidally important parameters were varied: Rp was independent (within limits) of (a) ionic strength, (b) pH, (c) initiator concentration (potassium persulfate), and (d) surfactant (sodium dodecyl sulfate) concentration; Rpp was independent (within limits) of (a) seed particle number concentration N, (b) oil:water phase ratio, and (c) monomer:polymer ratio; Rp was directly proportional to seed‐particle surface area. The viscosity average molecular weight of the polymer formed during interval II, Mv(i–j), was approximately constant and increased linearly with N. Log Mv(i–j) was inversely proportional to reaction temperature; Mv(i–j) was inversely proportional to initiator concentration. The overall activation energy of polymerization E′p was equal to the activation energy of propagation Ep during interval II. The value of kp at 60°C was 615 dm3 mol−1 s−1. Trace of oxygen seems to affect the average number of radicals per particle ī during interval II polymerization.

Effect of zinc-levulinic acid chelate compounds formed in furfuryl alcohol polymer concrete

As part of an experimental programme to develop high early strength water-compatible furfuryl alcohol (FA) polymer concrete (PC) composites, the polymerization heat resulting from the use of various mineral and organic acid initiators was measured using a differential scanning calorimeter. The results indicated that, of the several initiators evaluated, the use of 1,1,1-trichlorotoluene (TCT)-zinc chloride (ZnCl2) system to cure a FA-water-saturated aggregate system yielded the highest early strength and the highest polymerization heat. The ZnCl2 solution used as part of the two-component initiator systems had a significant effect on the rate of polymerization of the FA monomer and the thermal stability of the composite. The latter resulted from an increase in the stiffness of the polymer chains due to the formation of zinc-FA chelate compounds. These were formed through reactions between the bivalent metallic Zn2+ ions dissociated from the ZnCl2 solution and the strongly ionized carboxyl groups of levulinic acid yielded by the cleavage of furan rings in an acidic medium. The thermal polymerization activation energy of FA monomer combined with the TCT-ZnCl2 system was calculated to be 98.6 kJ mol−1. The glass transition temperature, T g, and thermal decomposition heat of the system were 62° C and 220 kJ kg−1, respectively.

Vinyl Polymerization. 404. Polymerization of Methyl Methacrylate Initiated with Substituted Imidazoles in an Aqueous Solution of Copper(II) Chloride

Abstract In order to study the effect of substituent groups of imidazole (Im) on the polymerization of methyl methacrylate (MMA) initiated with the system of Im compounds, copper(II) chloride, and water, polymerizations using N-ethylimidazole (N-Etlm) and 2-methylimidazole (2-MeIm) were carried out. The initiation ability for polymerization increased in the order 2-MeIm > N-Etlm > Im. The overall activation energies of polymerization initiated with N-Etlm and 2-MeIm were estimated to be 94.3 and 61.1 kJ/mol, respectively. The formation of complexes of the Cu(II) ion with substituted Im in water was confirmed by electronic spectra. Isolated complexes of [Cu(Im)4]Cl2, [Cu(2-MeIm)2]Cl2, [Cu(N-EtIm)2]Cl2, and [Cu(N-EtIm)4]Cl2, instead of free imidazoles, were used for the polymerization of MMA. These complexes, except [Cu(2-MeIm)2]Cl2, behaved as inhibitors of polymerization. This was due to the impossibility of formation of an adequate complex of MMA to initiate polymerization.

Kinetics of radical polymerization of 1-vinyl-1,2,4-triazole

Studies were made of kinetic features of radical polymerization of 1-vinyl-1,2,4-triazole and the molecular weight variation of poly-1-vinyl-1,2,4-triazole in water, in DMF and in DMAA. The rate of polymerization of the monomer in water and MW of the polymer obtained is higher than in other solvents. MW of poly-1-vinyl-1,2,4-triazole is proportional to the concentration of the monomer. It was shown that a typical feature of polymerization, which is general for all the solvents studied, is the existence of a reaction rate for the initiator with a reaction order higher than 0·5. The mechanism of monomolecular decay of macroradicals is discussed. The effective activation energy of polymerization was found.