Polymerization of methyl methacrylate in the presence of 2,5-di-tert-butyl-p-benzoquinone

Polymerization of methyl methacrylate in the presence of 2,5-di-tert-butyl-p-benzoquinone is a combination of two processes: inhibited and controlled radical polymerization. The adduct of chain propagation radicals and p-quinone formed due to the inhibited polymerization is a macroinitiator of controlled radical polymerization. The fraction of the pseudo-living process is determined by the concentration of p-quinone in the starting polymerized composition. Post-polymerization proceeds via the reversible inhibition mechanism.

     

Synthesis, Structure, and Magnetic Properties of Transition Metal Complexes of the Nitroxide 2,5-Dihydro-4,5,5-trimethyl-2,2-bis(2-pyridyl)imidazole-1-oxyl

With the radical 2,5-dihydro-4,5,5-trimethyl-2,2-bis(2-pyridyl)imidazole-1-oxyl (L) a series of transition metal complexes have been prepared: [ML(2)](SbF(6))(2) with M(2+) = Mn(2+) (1), Fe(2+) (2), Co(2+) (3), Ni(2+) (4), Cu(2+) (5), and Zn(2+) (6), Cu(L)(Cl)(2)(MeOH) (7), and Cu(L)SO(4).H(2)O (8). The structures of 1, 3, and 6 were determined by X-ray structural analyses. In these compounds the tridendate L is coordinated to the metal ion by the two pyridine nitrogen donors and by the oxygen atom of the nitroxide group. The N-O bond distances are 1.25(2) ? (1), 1.267(13) ? (3), and 1.260(11) ? (6). The M-O-N angles are 117.0(10) degrees (1), 114.5(8) degrees (3), and 114.2(7) degrees (6). Crystal data: space group P2(1)/n, for 1, 3, and 6; compound 1, a = 10.806(3) ?, b = 14.101(6) ?, c = 14.253(4) ?, beta = 108.82(2) degrees, V = 2055.7(12) ?(3), Z = 2, R(1) = 0.0677, wR(2) = 0.1512. Compound 3, a = 10.761(4) ?, b = 14.253(6) ?, c = 14.108(5) ?, beta = 111.16(3) degrees, V = 2017.9(13) ?(3), Z = 2, R(1) = 0.0702, wR(2) = 0.1460; compound 6, a = 10.788(2) ?, b = 14.147(3) ?, c = 14.196(3) ?, beta = 109.93(3) degrees, V = 2036.8(7) ?(3), Z = 2, R(1) = 0.0573, wR(2) = 0.1194. Magnetic measurements of 1, 2, 5, and 8 show strong antiferromagnetic interaction between the spin of the metal ion and the spin of the radical which increases at lower temperatures. For 6 the magnetic moment corresponds to two noninteracting spins in the temperature range 60-300 K.     

Polymerization of methyl methacrylate and styrene in the presence of polyimides containing aliphatic moieties in the backbone

The radical homopolymerization of methyl methacrylate and styrene in the presence of polyimide that contains aliphatic moieties and is dissolved in the monomer is studied. The viscosity characteristics, heat resistances, and thermal stabilities of the resulting polymers and their solubilities in organic solvents are examined. It is found that the products of radical polymerization are polyimide-poly(methyl methacrylate) and polyimide-polystyrene copolymers, whose properties differ from those of the respective unmodified polymerization and polycondensation polymers.     

Carbon-chain polymers and copolymers Communication 8. Polymerization of styrene and methyl methacrylate in solution in the presence of tributylboron

Summary The polymerization of methyl methacrylate and styrene in toluene was studied in the presence of tributyl-boron and the basic laws of these processes were determined.     

Photo-living radical polymerization of methyl methacrylate by 2,2,6,6-tetramethylpiperidine-1-oxyl in the presence of a photo-acid generator

The novel photo-living radical polymerization of methyl methacrylate (MMA) was determined using 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMDV) and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) in the presence of bis(alkylphenyl)iodonium hexafluorophosphate (BAI). The polymerization provided a comparatively narrow molecular weight distribution in the range of 1.4–1.7. The resulting PMMA contained no BAI fragments in its structure and had the 1-cyano-1,3-dimethyl-3-methoxybutyl radical and MTEMPO at the 1:1 molar ratio. The experimental molecular weight was in close agreement with the theoretical one when the initiator efficiency was taken into consideration. The plots of ln([MMA]₀/[MMA]) vs. time and the molecular weight of PMMA vs. the conversion and vs. the reciprocal of the initial concentration of AMDV showed linear correlations, indicating that the polymerization proceeded in accordance with a living mechanism. It was found that the polymerization had a photo-switching ability, because the polymerization was interrupted by turning off the irradiation, and then restarted by the irradiation again.     

Free-radical copolymerization of methyl methacrylate with styrene in the presence of 2-mercaptoethanol II. Influence of methyl methacrylate/styrene ratio

The free-radical copolymerization of methyl methacrylate (MMA) with styrene (St) in the presence of 2-mercaptoethanol (ME) was investigated in order to obtain ω-hydroxy oligomers with random copolymer-type chains of various compositions and molecular weights. Polymerizations at three different MMA/St molar ratios were carried out, while keeping constant the ME/monomer ratio. Monomer mixtures richer in MMA than in St were employed in order to attempt preparing lower polydispersity oligomers with monomodal molecular weight distribution (MWD). The molecular weights of the resulting oligomers increased with both conversion and MMA fraction in the feed, while polydispersities increased with conversion and decreased with MMA concentration in the initial monomer mixture. For the lower MMA fractions in the monomer feed, bimodal MWDs resulted beyond a certain conversion due to the faster relative consumption of ME than of monomer. Based on the pseudo-kinetic rate constant method, apparent chain transfer constants corresponding to the three different compositions of the monomer feed were estimated. The values obtained were in good agreement with the evolution of molecular weights and polydispersities with conversion and MMA fraction in the monomer feed. The co-oligomers prepared displayed functionalities around unity, making them suitable for the synthesis of macromonomers.     

Stable aziridinium salts of oxalic and 2,5-dihydro-4,5,5-trimethyl-2-oxo-5-furancarboxylic acids

Conclusions Stable salts of aziridine, 2-methylaziridine, and 2,2-dimethylaziridine with the oxalic and 2,5-dihydro-4,5,5~trimethyl-2-oxo-5-furancarboxylic acids were obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 192–194, January, 1983.     

Polymerization of coordinated monomers. XVI. Stereoregulation in the alternating copolymerization of methyl methacrylate with styrene in the presence of metal halides

Triad cotacticities of alternating copolymers of methyl methacrylate with styrene prepared in the presence of zinc chloride, ethylaluminium sesquichloride, and ethylboron dichloride are investigated from the mechanistic point of view by means of ¹H- and ¹³C-NMR. The cotacticities from ¹H-NMR spectra are obtained accurately by using α-d-styrene in the place of styrene and by measuring the spectra on the copolymer in o-dichlorobenzene at 170°C. The relative intensities of three peaks of the splitting signal for the methoxy protons in the nonalternating copolymers obtained by the use of benzoyl peroxide in the absence of metal halides agree well with the cotacticity distribution calculated theoretically by the Lewis-Mayo mechanism with the stereoregulation following Bernoullian statistics. The splitting signals in the ¹H- and ¹³C-NMR spectra of the alternating copolymers prepared in the presence of metal halides cannot be explained by the same mechanism. The relative intensities of three peaks of the splitting signals for the methoxy protons and for the carbonyl carbon in the methyl methacrylate unit (the contents of cotactic triads centered by the methyl methacrylate unit) are not equal to those for the aromatic C₁ carbon in the styrene unit (the contents of cotactic triads centered by styrene unit). The value of f²Y - 4fxfz is not equal to zero, where fx, fy, and fz are the cosyndiotactic, coheterotactic, and coisotactic triad contents, respectively, in the alternating copolymer. Copolymers obtained in the presence of zinc chloride are not exactly equimolar alternating but always contain a methyl methacrylate unit in excess, and the relative intensities of the three peaks for the aromatic C₁ carbon change with the copolymer composition. These results are explained by a proposed mechanism: the alternating copolymerization proceeds through the homopolymerization of a ternary molecular complex composed of a metal halide, methyl methacrylate, and styrene, accompanied with the stereoregulation following first-order Markovian statistics; the increase of methyl methacrylate content in the copolymer prepared in the presence of zinc chloride is caused by the participation of the binary molecular complex composed of a metal halide and methyl methacrylate in addition to the ternary molecular complex.     

Semi-continuous emulsion polymerization of styrene in the presence of poly(methyl methacrylate) seed particles. Polymerization conditions giving core-shell particles

This work reports the morphology of two-phase latex particles prepared by semi-continuous seed emulsion polymerization of styrene in the presence of polar poly(methyl methacrylate), PMMA, seed particles, using different conditions of non-polar styrene feed rate, rate of initiation, seed particle concentration and temperature of polymerization.The expected latex particle morphology at thermodynamic equilibrium is an inverted core-shell structure where the non-polar polystyrene would form the core. However, depending on the set of process conditions used the morphology of the resulting two-phase particles varied from that of a pure core-shell structure, over intermediate structures in which a shell of PS surrounded a PMMA core containing an increasing number of PS phase domains, to a structure in which the entire PS phase was present as discrete PS phase domain, more or less evenly distributed in a matrix of PMMA.By the use of a caloirimetric reactor system the monomer concentration in the particles during the different polymerization experiments could be calculated by comparing the integral of the polymerization rate curve with the integral of the monomer feed rate. A comparison between particle morphology and the calculated concentration of plasticizing monomer in the polymerizing particles strongly suggested that the diffusivity of the entering oligo radicals determined by the difference between polymerization temperature and the glass transition temperature of the monomer-swollen core polymer is a key factor determining the morphology of two-phase particles prepared by semi-continuous seed emulsion polymerization.Two-phase particles with a true core-shell structure were obtained in experiments where the estimated glass transition temperature of the PMMA phase was only a few degrees below the polymerization temperature. The results show that such particles can be obtained under conditions of high as well as low styrene feed rates, provided that the rate of initiation is properly adjusted.     

Specifics of radical polymerization of styrene and methyl methacrylate in the presence of ruthenium carborane complexes

The specifics of the radical polymerization of styrene and methyl methacrylate in the presence of ruthenium closo- and exo-nido-carborane complexes with phosphine and diphosphine ligands were investigated. It was shown that, depending on a coinitiator, the polymerization proceeds through the atom transfer radical mechanism or the reverse atom transfer radical mechanism to high conversions without gelation to yield macromolecules with a low polydispersity. The influence of the ligand environment, the oxidation state of ruthenium atoms in the carborane complexes, and the temperature conditions on the specific features of the polymer synthesis was established.     

Mechanism of alternating copolymerization of methyl methacrylate with styrene in the presence of diethylaluminum chloride

A kinetic study of the propagation mechanism of the alternating copolymerization of styrene (St) with methyl methacrylate (MMA) in the presence of a complexing agent (diethylaluminum chloride, DEAC) in bulk and in tetrachloroethylene solutions at a molar ratio DEAC/MMA = 0.5 has been carried out. It has been shown that the copolymerization is a chain radical process characterized by a short active-center lifetime, bimolecular termination, and high rate of chain transfer to the complexed MMA. A kinetic scheme has been proposed for the propagation mechanism of alternating copolymerization in the presence of a complexing agent not requiring independent measurements of the equilibrium constant of complexation. It has been found that spontaneous and UV-initiated copolymerizations in the system have different mechanisms of initiation and a common mechanism of propagation. The propagation proceeds by addition of single monomers as well as donor-acceptor complexes of the comonomers to the propagation radicals, with the first mechanism being predominant. Inclusion of the monomers in the complex leads to an increase of the St reactivity and to a decrease of the MMA reactivity in propagation to the corresponding macroradicals in comparison with the reactivity of the free monomers. A number of kinetic and statistical parameters of the propagation reaction have been calculated.     

Controlled synthesis of styrene and methyl methacrylate copolymers in the presence of reversible addition-fragmentation chain-transfer agents

Molecular-mass characteristics of styrene-methyl methacrylate copolymers formed via the reversible addition-fragmentation chain transfer copolymerization mediated by dithiobenzoates have been studied. Low-molecular-mass reversible-addition fragmentation chain-transfer agents active in the homopolymerization of both monomers and in the homopolymerization of only one of the monomers (styrene) can be used for the controlled synthesis of narrow dispersed copolymers. Conditions for the synthesis of narrow dispersed block copolymers with the desired structure and molecular mass of the blocks have been found. The polymer reversible addition fragmentation chain-transfer agent determines the composition and molecular mass of the first block. The structure of the second block is defined by the composition of the monomer mixture, and the molecular-mass characteristics are set by the concentration of the agent and the conversion of monomers.     

Copolymerization of diallyl isophthalate with methyl methacrylate and styrene in the presence of C60 fullerene

The involvement of fullerene in the radical copolymerization of diallyl isophthalate with methyl methacrylate or styrene results in a change in the relative activity of monomers owing to the interaction of C₆₀ with the allyl radical yielding a “quo;new,”quo; more active radical. This corresponds to the transition from degradative chain transfer to effective transfer to the allyl compound. It is of great importance that, at an amount of diallyl isophthalate in the monomer mixture of up to 10 mol %, C₆₀ fullerene is almost completely incorporated into macromolecules.     

Emulsion copolymerization of styrene and methyl methacrylate

Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10^?5 for styrene polymerization and 0.4 × 10^?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10^?5. Reactivity ratios measured in emulsion were r₁ (styrene) = 0.44, r₂ = 0.46. Those in bulk polymerizations were r₁ = 0.45, r₂ = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known.     

Mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the presence of dicyclopentadienyltitanium dichloride

The mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the presence of dicyclopentadienyltitanium dichloride (Cp₂TiCl₂) was studied using quantum chemical calculations and electron spin resonance spectroscopy. It was established that the reduction of Cp₂TiCl₂ to Cp₂TiCl during the macromolecule synthesis occurs through the living polymerization mechanism, which adjusts the growth of a polymeric chain. The geometrical structures of the molecular complexes between a growing macroradical and Cp₂TiCl₂ and transition states of radical inhibition steps were optimized and the thermodynamic and kinetic parameters of the elementary reactions were estimated for several feasible directions of the process. On this basis, the observed kinetic features of vinylic monomer polymerization with participation of organic compounds of titanium are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Reverse atom transfer radical random copolymerization of styrene and methyl methacrylate in the presence of diatomite nanoplatelets

Diatomite nanoplatelets were used for in situ random copolymerization of styrene and methyl methacrylate by reverse atom transfer radical polymerization to synthesize different well‐defined nanocomposites. Inherent features of the pristine diatomite nanoplatelets were evaluated by Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherm, scanning electron microscope, and transmission electron microscope. Gas and size exclusion chromatography was also used to determine conversion and molecular weight determinations, respectively. Considerable increment in conversion (from 81% to 97%) was achieved by adding 3 wt% diatomite nanoplatelets in the copolymer matrix. Moreover, molecular weight of random copolymer chains was increased from 12 890 to 13 960 g·mol⁻¹ by addition of 3 wt% diatomite nanoplatelets; however, polydispersity index (PDI) values increases from 1.36 to 1.59. Proton nuclear magnetic resonance spectroscopy was used to evaluate copolymers composition. Thermal gravimetric analysis results indicate that thermal stability of the nanocomposites is improved by adding diatomite nanoplatelets. Differential scanning calorimetry shows an increase in glass transition temperature from 66°C to 71°C by adding 3 wt% of diatomite nanoplatelets.