Solution polymerization of methyl methacrylate using trioctylmethylammonium persulfate initiator: Kinetics of polymerization and activation parameters for the primary decomposition of the initiator

The kinetics of solution polymerization of methyl methacrylate using trioctylmethylammonium persulfate (aliquat persulfate) at 60°C has been studied in t-butyl alcohol, N,N-dimethyl formamide, acetonitrile, dioxane, acetone, and methyl ethyl ketone. The rate of polymerization depends markedly on the solvent used. The initiator exponent is close to 0.5 in the first three solvents but larger than this value in the other three solvents. The overall activation energy of the polymerization has been determined in all the solvents. The rate constants and activation parameters for the primary decomposition of the initiator have been determined in the first three solvents where ideal polymerization conditions prevail. The activation parameters for the decomposition of AQ₂S₂O₈ in the organic solvents depend on the type of solvent. They are very different from those of the free S₂O^2?₈ ion in water. These differences have been explained taking into consideration the various ionic forms in which the initiator exists in the studied solvents using a previously postulated model of the activated state.     

Studies on the polymerization of methyl methacrylate activated by azobisisobutyramidine

Kinetic studies on methyl methacrylate polymerization were carried out with watersoluble 2,2′-azobisisobutyramidine (ABA). The rate of polymerization was proportional to the square root of the initiator concentration in the solvents chloroform, methanol, and dimethyl sulfoxide (DMSO), which confirms the bimolecular nature of the termination reaction. The monomer exponent was unity in chloroform but in methanol and DMSO the rate of polymerization passed through a maximum when plotted against the monmer concentration. This behavior in methanol has been attributed to be due to the enhanced rate of production of radical with increasing proportion of methanol. The rate of decomposition of the ABA has been observed to be faster in methanol than in chloroform. The situation becomes more complicated with DMSO, which was found to reduce the value of δ = (2k_t)^1/2/k_p in methyl methacrylate polymerization. The rate of polymerization was observed to be highly dependent on the nature of the solvent, the rate increasing with increased electrophilicity of the solvent. The dependence of R_p on the solvent has been explained in the light of the stabilization of the transition state due to increased solvation of the basic amidine group of the initiator with the increased electrophilicity of the solvent.     

Kinetic studies on the imine base/isocyanate‐induced radical polymerization of vinyl monomers

Specific imine bases (IB) in conjunction with various isocyanates (IC) mediate the radical polymerization of radically polymerizable monomers such as methyl methacrylate (MMA). Advantageously, the 2‐(methylmercapto)‐2‐thiazoline MMT/IC combination as initiator works even at room temperature for polymerization of MMA. The coefficients a, b, and c of the basic rate law of monomer consumption d[M]/dt = k_p·[IC]^a·[IB]^b·[M]^c were determined. The order a has been determined to 0.5 showing the root law of radical polymerization with respect to the IC component as initiator. Moreover, b and c amount 1. The initiator combination MMT/ IC was applied to determine the influence of the molecular structure of the IC on the rate of monomer conversion. For aromatic isocyantes, the gross rate constant of monomer consumption correlates with the Hammet constant of aromatic substituents. The activation energies of the gross polymerization rate constant of several initiator mixtures were determined whereby the value of E_A,Br was found to be between typical values of radical polymerization initiated by photochemical reactions (～20 kJ/mol) and commonly used thermal decomposing initiators (～80 kJ/mol). Presumptions on the initiating and terminating step of the IB/IC mediated polymerization were done by means of electrospray ionization mass spectrometry, NMR spectroscopy, and the elemental composition of the head and end group of the resulting polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of metal salts on polymerization. Part I. Polymerization of vinylpyridine initiated with cupric acetate

The polymerization of vinylpyridine initiated by cupric acetate has been studied. The rate of polymerization was greatly affected by the nature of the solvent. In general polar solvents increased the rate of polymerization. Polymerization was particularly rapid in water, acetone, and methanol. The initial rate of polymerization of 4-vinylpyridine (4-VP) in a methanol–pyridine mixture at 50°C. is R_p = 6.95 × 10^?6[Cu¹¹]^1/2 [4-VP]² l./mole-sec. The activation energy of initiation by cupric acetate is 5.4 ± 1.6 kcal./mole. Polymerization of 2-vinylpyridine and 2-methyl-5-vinylpyridine with the same initiator was much slower than that of 4-VP. Dependence of R_p on monomer structure and solvent is discussed. Kinetic and spectroscopic studies led to the conclusion that the polymerization of 4-VP is initiated by one electron transfer from the monomer to cupric acetate in a complex having the structure, (4-VP)₂Cu(CH₃COO)₂.     

Catalytic Action of Metallic Salts in Autoxidation and Polymerization. VII. Polymerization of Methyl Methacrylate by Cobalt(ll) or (III) Acetylacetonate-Dioxane Hydroperoxide

Abstract

Polymerization of methyl methacrylate by Co(II or III) acetylacetonate-dioxane hydroperoxide [abbreviated as Co(acac)2, Co(acac)₃, and DOX HPO, respectively] was carried out in dioxane solvent, and the differences in polymerization rate and the degree of polymerization between two initiating systems were compared. Co(acac)₂-DOX HPO for the initiation of the polymerization system was more effective than Co(acac)₃-DOX HPO. The polymerization rate equations for both initiating systems obtained from kinetic data were as follows. For Co(acac)₂-DOX HPO initiating system: R_p=k [M]^3/2[Co(acac)₂]^1/7[DOX HPO]^?     

Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3]− on γ‐Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N‐Dimethylformamide

Summary: Radiation‐induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N‐dimethylformamide (DMF) in the presence of ionic liquid [Me₃NC₂H₄OH]⁺[ZnCl₃]⁻ is reported. A substantial increase in monomer conversion and molecular weight is observed at room‐temperature ionic liquid (RTIL) >60 vol.‐%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid.

Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100.     

Studies on polymers containing functional groups. VI. Kinetics of the polymerization and copolymerization behaviors of o-hydroxystyrene

Some kinetic studies were made of the homopolymerization of o-hydroxystyrene and its copolymerization behavior with styrene and methyl methacrylate in tetrahydrofuran using azobisisobutyronitrile as initiator were done. The rate of polymerization experimentally obtained is given by R_p = K[M][I]^0.72. Accordingly, it is likely that the growing chain radicals are terminated not only by mutual termination but also by a chain-transfer mechanism, the latter occupying a considerable portion. The latter is mostly attributed to the transfer to monomer, i.e., C_m for o-hydroxystyrene was 1.3 × 10^?2. Some transfer mechanisms were assumed, although it is difficult to elucidate the mechanism in detail, owing to its complexity. Effects of solvent on the rate of polymerization were examined, dioxane, methyl ethyl ketone, ethanol, and tetrahydrofuran being used. However, no differences were found among the solvents. The apparent activation energy of polymerization was found to be 21.5 kcal./mole. Monomer reactivity ratios and Alfrey-Price Q–e values for o-hydroxystyrene were determined. The Q–e values (Q = 1.41, e = ?1.13) are rather similar to those of p-methoxystyrene. Thus, the e value for o-hydroxystyrene is more negative than that for styrene.     

Kinetic and particle size studies of emulsion polymerization of methyl methacrylate and styrene with using polyamidoamine dendrimer as seed

The emulsion polymerization of methyl methacrylate (MMA) and styrene (St) were investigated with using polyamidoamine (PAMAM) dendrimer as seed, potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier. The effects of 4.0GPAMAM dendrimer concentration, initiator concentration, emulsifier concentration, monomer concentration, and polymerization temperature on the monomer conversion and polymerization rate were investigated. At the same time, the influence of the generation of PAMAM dendrimer on latex particle size was studied also. The results showed that the monomer conversion and polymerization rate increased with increasing initiator concentration, emulsifier concentration, monomer concentration, and polymerization temperature. But polymerization rate increased firstly with an increase in the 4.0GPAMAM dendrimer from 0.03 g to 0.09 g and then decreased with further increase to 0.12 g. When the concentration of 4.0GPAMAM dendrimer less than 1.449 × 10^?4 mol/L, the kinetic equation can be expressed by Rp∝[4.0GPAMAM]^0.772[SDS]^0.562[KPS]^0.589[M]^0.697, and the activation energy (Ea) of emulsion polymerization is 62.56kJ/mol. In additional, the copolymer latex particle size decreased and possessed monodispersity with increasing the generation of PAMAM dendrimer. According to FT-IR spectrum analysis, PAMAM dendrimer is successfully incorporated into the poly(PAMAM-St–MMA) latex particles.     

Synthesis of poly(methyl methacrylate) via ARGET ATRP and study of the effect of solvents and temperatures on its polymerization kinetics

This investigation reports the synthesis of poly(methyl methacrylate) via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and studies the effect of solvents and temperature on its polymerization kinetics. ARGET ATRP of methyl methacrylate (MMA) was carried out in different solvents and at different temperatures using CuBr₂ as catalyst in combination with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a ligand. Methyl 2‐chloro propionate was used as ATRP initiator and ascorbic acid was used as a reducing agent in the ARGET ATRP of MMA. The conversion was measured gravimetrically. The semilogarithmic plot of monomer conversion versus time was found to be linear, indicating that the polymerization follows first‐order kinetics. The linear polymerization kinetic plot also indicates the controlled nature of the polymerization. N,N‐Dimethylformamide (DMF), tetrahydrofuran (THF), toluene, and methyl ethyl ketone were used as solvents to study the effect on the polymerization kinetics. The effect of temperature on the kinetics of the polymerization was also studied at various temperatures. It has been observed that polymerization followed first‐order kinetics in every case. The rate of polymerization was found to be highest (k_app = 6.94 × 10⁻³ min⁻¹) at a fixed temperature when DMF was used as solvent. Activation energies for ARGET ATRP of MMA were also calculated using the Arrhenius equation.     

Free-radical polymerizations initiated by triethylaluminum–cuprous chloride mixtures

Methyl methacrylate was polymerized by triethylaluminum—cuprous chloride catalyst. A study of the polymerization kinetics indicated that the overall rate was represented by the equation, R_p = K[AlEt₃] [CuCl]^½ [M]². The overall activation energy was 16.5 kcal/mole. From ESR measurement and the results of copolymerization of methyl methacrylate with styrene, it was suggested that the catalytic system has the character of a radical initiator. A polymerization scheme was also proposed.     

Phase-Transfer-Agent-Aided Free Radical Polymerization of Methyl Methacrylate-A Kinetic Study

The kinetics of phase-transfer-agent-aided free radical polymerization of methyl methacrylate was investigated by using K₂S₂O₈ as the initiator and cetyltrimethyl ammonium chloride (Arquad) as the phase transfer agent. The rate of polymerization was found to be proportional to [M]^1.23[K₂S₂O₈]^0.8 [Arquad]^0.25 and almost independent of the volume of water (V _w)/volume of organic solvent (V _o) (benzene) ratio for V _w/V _o < 0.33. A reaction mechanism is proposed.     

4-N,N-Dimethylamino-4'-Isopropylbenzophenone as polymerization photoinitiator. Effect of solvent and photoinitiator concentration on its photoreactivity and on the polymerization process

Several kinetics aspects of the methyl methacrylate (MMA) polymerization using 4-dimethylamino-4'-isopropylbenzophenone (PI) as photoinitiator have been studied. The order of the polymerization reaction with respect to monomer and initiator concentrations have been investigated, as well as the polymerization behavior under well-stirred and unstirred conditions; values of initiation quantum yield (?_i) and k_p/k_t^1/2 have also been determined. It has been found that the nature of the polymerization-initiating radicals depends on the type of solvent and the photoinitiator concentration ([PI]). In cyclohexane solution and at low [PI] (< 5 x 10^-5M), the cyclohexyl radical is practically the only polymerization initiating radical, while at higher [PI] both radicals, cyclohexyl and the aminoalkyl derived from PI, participate in the initiation step, increasing the participation of the later as the [PI] increases. When benzene is used as solvent both phenyl and aminoalkyl radicals participate in the initiation step at any [PI] employed. Efficiencies of the radicals derived from solvent and photoinitiator have been determined.     

Vinyl polymerization with a binary system of p‐chlorobenzenediazonium salt and sodium tetraphenylborate

A combined system of sodium tetraphenylborate (STPB) and p‐chlorobenzenediazonium tetrafluoroborate (CDF) serves as an effective initiator at low temperatures for acrylate monomers such as methyl methacrylate (MMA), ethyl acrylate, and di‐2‐ethylhexyl itaconate. The polymerization of MMA with the STPB/CDF system has been kinetically investigated in acetone. The polymerization shows a low overall activation energy of 60.3 kJ/mol. The polymerization rate (R_p) at 40 °C is given by R_p = k[STPB/CDF]^0.5[MMA]^1.6, when the molar ratio of STPB to CDF is kept constant at unity, suggesting that STPB and CDF form a complex with a large stability constant and play an important role in initiation and that MMA participates in the initiation process. From the results of a spin trapping study, p‐chlorophenyl and phenyl radicals are presumed to be generated in the polymerization system. A plausible initiation mechanism is proposed on the basis of kinetic and electron spin resonance results. A large solvent effect on the polymerization can be observed. The largest R_p value in dimethyl sulfoxide is 11 times the smallest value in N,N‐dimethylformamide. The copolymerization of MMA and styrene with the STPB/CDF system gives results somewhat different from those of conventional radical copolymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4206–4213, 2001     

Effects of mercaptides on anionic polymerization. III. Polymerization of methyl methacrylate by thiophenoxides in polar aprotic solvents

Sodium thiophenoxide initiated the polymerization of methyl methacrylate in polar aprotic solvents (DMF, DMSO, HMPA). The active species that initiated the polymerization of the monomer was found by spectrophotometric measurements and by the sodium fusion method to be sodium thiophenoxide itself. The activation energy for the polymerization of the monomer in DMF solvent obtained was E = 3.4 kcal/mole below 30°C, and E = ?3.3 kcal/mole above the temperature. The phenomena were reasoned as the result of the formation of two active species: a solvent-separated ion pair and a contact ion pair. The effects of counterions on the reactivity of thiophenoxide increased with increasing electropositivity of the metals: Li < Na < K. Sodium phenoxide, the oxygen analog of thiophenoxide, was also found to initiate the polymerization of the monomer in the solvents. The relative reactivity of thiophenoxide to phenoxide for the monomer in HMPA at 30°C was thus determined: phenyl-SNa > phenyl-ONa. The relative effect of the polar aprotic solvents on the reactivity of thiophenoxide was also as follows: HMPA > DMF > DMSO. The kinetic studies were made by the graphical evaluation of rate constants. The following results were obtained for the monomer at 20°C in DMF solvent: K_p = 3.5 × 10² 1./mole-hr and K_t = 9.8 × 10^?2/hr.     

[Hydroxy(tosyloxy)iodo]benzene as Thermal initiator for the Radical Polymerization of Methyl Methacrylate

Abstract

The thermal polymerization of methyl methacrylate in a solution of N,N-dimethylacetamide has been studied using [hydroxy(tosyloxy)- iodo]benzene (HTIB) as the initiator. The rate of polymerization was a direct function of the monomer and initiator concentrations. The initiator and monomer exponent values expressing this dependence were found to be 1.0 and 0.8, respectively. The overall activation energy of polymerization was estimated to be 45 kJ·mol^?-1. The polymerization was inhibited in the presence of hydroquinone. The effect of various solvents on the polymerization rate was studied. The polymer prepared with HTIB (0.47 × 10^?3 mol·L^?-1) had a number-average molecular weight of 138,000 and a glass transition temperature of 106°C. The polymer showed good thermal stability as determined by thermogravimetric analysis.     

Photopolymerization of methyl methacrylate using a morpholine–sulfur dioxide charge-transfer complex as the photoinitiator

Photopolymerization of the vinyl monomer (M) of methyl methacrylate (MMA) was kinetically studied by using near-UV/visible light at 40°C and employing a morpholine (MOR)–sulfur dioxide (SO₂) charge-transfer (C-T) complex as the photoinitiator. The rate of polymerization (R_P) was found to be dependent on the morpholine: sulfur dioxide mole ratio; the 1 : 2 (MOR–SO₂) complex acted as the latent initiator complex C which underwent further complexation with the monomer molecules to give the actual initiating complex I. Using the 1 : 2 (MOR–SO₂) C-T complex as the latent initiator, the observed kinetics may be expressed as R_P [MOR–SO₂]^0.27[M]^1.10. Benzoquinone behaved as a strong inhibitor. Polymers obtained tested positive for the incorporation of a sulphonate-type end group. Polymerization followed a radical mechanism. Kinetic nonideality as revealed by a low initiator exponent and monomer exponent of greater than unity was explained on the basis of a prominent primary radical termination effect. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1973–1979, 1998     

Studies on Polymerization of Vinyl Compounds Initiated by Metal Chelate II Kinetics of Polymerization of Methyl Methacrylate Initiated by Nickel Ethyl Acetoacetate in the Presence and the Absence of Aromatic Amines

The kintetic studies of polymerization of methyl methacrylate initiated with nickel ethyl acetoacetate gave the following equations. R_p=K₁[Monomer]^1.4[Chelate]^0.5, in the absence ox aniline R_p=K₂[Monomer]^1.2[Chelate]^0.5 [Aniline]^0,5, in the presence of aniline. Some aromatic amines such as aniline markedly accelerated the polymerization, while pyridine had no such effect. The activation energy of initiation was 24.8 kcal/mol in the absence of aniline, and 8.8 kcal/mol in the presence of aniline. Both the kinetic data and the infrared spectra of the polymer indicated that the polymerization was radical in nature. The reaction order against monomer varied, as the temperature differed. The spectrophotometric investigation indicated formation of a complex between the chelate and the monomer, or amines. It also showed that the formation of a complex was not a factor which controlled the rate of initiation. A scheme of initiation mechanism was presented on the basis of the above experimental evidence.     

Iron‐mediated AGET ATRP of methyl methacrylate in the presence of polar solvents as ligands

The polar solvents, N‐methylpyrrolidone (NMP), N,N‐dimethylformamide (DMF), and acetonitrile (CH₃CN) were used as ligands for iron(III)‐mediated activators generated by electron transfer atom transfer radical polymerizations (AGET ATRPs) of methyl methacrylate (MMA) with various initiators and reducing agents. Polymerizations were conducted with a molar ratio of [MMA]₀/[initiator]₀/[FeBr₃]₀/[reducing agent]₀ = 100:1:1:0.5 and a volume ratio of MMA/solvent = 2:1 at 60 °C to investigate the effects of initiator, solvent and reducing agent, and most of the systems showed the typical features of “living”/controlled radical polymerization. In order to get a deeper understanding of the mechanism, the amount of the reducing agent was changed to study the polymerization behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1020–1027     

Vinyl polymerization. 275. Polymerization of vinyl monomers photosensitized by tetramethyltetrazene

A study of the photopolymerization of vinyl monomers in the presence of tetramethyltetrazene (TMT) was made. TMT was found to act as an effective sensitizer. In the photopolymerization of vinyl monomers such as methyl methacrylate or styrene the rate of polymerization was expressed by the equation: R_p = k[TMT]^1/2[monomer]. The chain-transfer constant of TMT under ultraviolet irradiation was estimated to be 3.8 × 10^?2 for the above monomers. A linear correlation was found to exist between the reactivity of dimethylamino radical toward the vinyl monomers and e values for the corresponding monomers.     

Role of dimethyl sulfoxide as a solvent for vinyl polymerization

Dimethyl sulfoxide has been used as a solvent in the polymerization of methyl methacrylate and styrene. The chain-transfer coefficients of the solvent and the values of δ [i.e., (2k_t)^1/2/k_p] in solvent-monomer mixtures of various compositions were determined. δ was observed to be dependent on the solvent concentration in the case of methyl methacrylate but remained constant in case of styrene. The lowering of the values of δ with increasing solvent concentration in case of methyl methacrylate has been attributed to an interaction between the solvent and poly(methyl methacrylate) radical resulting in lower termination rate.