Controlled radical polymerization of methacrylates of various structures in the presence of the AIBN-FeCl3-N,N-dimethylformamide catalytic system

The controlled radical polymerization of methyl methacrylate, 2-ethoxyethyl methacrylate, and tert-butyl methacrylate conducted via atom-transfer radical polymerization in the presence of the AIBN-FeCl₃· 6H₂O-N,N-dimethylformamide catalytic system is studied. For all the systems under study, the rate of reaction is first order with respect to the monomer concentration. The number-average molecular mass of the polymers linearly increases with conversion, and their polydispersity indexes are below 1.6. The rate of polymerization decreases in the following sequence: 2-ethoxyethyl methacrylate > methyl methacrylate > tert-butyl methacrylate. The presence of ω-terminal chlorine atoms in polymer macromolecules is confirmed by ¹H NMR spectroscopy and through the block copolymerization of methyl methacrylate with a poly(ethoxyethyl methacrylate)-based macroinitiator.     

Poly[N-(2-hydroxypropyl)methacrylamide]—I. Radical polymerization and copolymerization

The radical polymerization of N-(2-hydroxypropyl)methacrylamide was investigated kinetically. The hydrophilic character of the polymerization medium was found to affect the rate of decomposition of the initiator [2,2′-azobis(methyl isobutyrate)] and the course of primary radical termination. The presence of the -OH group in the alkyl group attached to the nitrogen atom leads to an increase in the molecular weight of the polymer in comparison with polymers of N-alkyl methacrylamides. This phenomenon was interpreted in terms of the possibility of a polymeranalogous transesteramidation and of an increased possibility of transfer to monomer and polymer. The copolymerization parameters of N-(2-hydroxypropyl)methacrylamide (M₁) with methyl methacrylate and styrene were determined; in the first case, r₁ = 0·84 ± 0·05, r₂ = 0·66 ± 0·07; in the second case, r₁ = 0·53 ± 0·08, r₂ = 1·72 ± 0·19.     

Synthesis of Graft Polymers by Copolymerization of Macromonomers. II. Copolymerization Kinetics of Styrene-and Methacrylate-Terminatedpoly(2-Acetoxyethyl Methacrylate) Macromonomers

Styrene-terminated poly(2-acetoxyethyl methacrylate) macromonomer (EBA), methacrylate-terminated poly(2-acetoxyethyl methacrylate) macromonomer (MPA), and methacrylate-terminated poly(methyl methacrylate) macromonomer (MPM) were synthesized and subjected to polymerization and copolymerization by a free-radical polymerization initiator (AIBN). EBA and MPA were homopolymerized at various concentrations. EBA exhibited higher reactivity than styrene. The reactivity of MPA, however, was almost equal to that of glycidyl methacrylate. Cumulative copolymer compositions were determined by GPC analysis of copolymerization products. The reactivity ratios estimated were r_a = 0.95 and r_b , = 0.90 for EBA macromonomer (a)-methyl methacrylate (b) copolymerization. These values were not consistent with literature values for the styrene-methyl methacrylate and p-methoxy-styrene-methyl methacrylate systems. The reactivity ratios estimated for MPA and 2-bromoethyl methacrylate were r_a - 0.95 and r_b , = 0.98; equal to the glycidyl methacrylate-2-bromoethyl methacrylate system. MPA or MPM was also copolymerized with styrene, and the reactivity ratios were r_a = 0.40, r_a = 0.60 and r_a = 0.39, r_a = 0.58, respectively. These estimates were in good agreement with the reactivity ratios for glycidyl methacrylate and styrene. Thus, no effect of molecular weight was observed for both copolymerization systems.     

Effect of monomer/nanoclay interaction on the kinetics of atom transfer radical homo- and copolymerization of styrene and methyl acrylate

Atom transfer radical homo- and copolymerization of styrene and methyl acrylate initiated with CCl₃-terminated poly(vinyl acetate) macroinitiator were performed at 90°C in the presence of nanoclay (Cloisite 30B). Controlled molecular weight characteristics of the reaction products were confirmed by GPC. It was shown that nanoclay slightly decreased the rate of styrene polymerization, while it significantly enhanced the rate of methyl acrylate polymerization and its copolymerization with styrene. The reactivity ratios of the monomers in the presence and in the absence of nanoclay were calculated (r _St = 1.002 ± 0.044, r _MA = 0.161 ± 0.018 by extended Kelen-Tudos method and r _St = 1.001 ± 0.038, r _MA = 0.163 ± 0.016 by Mao-Huglin method), confirming that the presence of nanoclay has no influence on monomer reactivity. The enhancement in the homopolymerization rate of methyl acrylate as well as its copolymerization rate with styrene was attributed to nanoclay effect on the dynamic equilibrium between active (macro)radicals and dormant species. Dipole moments of the monomers were successfully used to predict structure of the polymer/clay nanocomposites prepared via in situ polymerization.     

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.     

Photo-living radical polymerization of methyl methacrylate by a nitroxide mediator

The novel photo-living radical polymerization was determined using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) and bis(alkylphenyl)iodonium hexafluorophosphate (BAI) as the photo-acid generator. The polymerization of methyl methacrylate was performed using azobisisobutylonitrile as an initiator in the presence of MTEMPO and BAI at room temperature by irradiation with a high-pressure mercury lamp to produce poly(methyl methacrylate) with a comparatively narrow molecular weight distribution (M _w/M _n?=?1.3–1.7). The polymerization proceeded by a living mechanism based on the fact that the first-order time-conversion plots linearly increased. A linear increase in the plots of the molecular weight versus the conversion also supported the living nature of the polymerization. It was found that MTEMPO had an interaction with the propagation chain end to control the molecular weight, while BAI weakened the interaction of MTEMPO with the propagation chain end to reduce the molecular weight distribution and polymerization time.     

Copolymerization of styrene with methyl methacrylate in the presence of the system tributylborane–<Emphasis Type="Italic">p</Emphasis>-quinone

The copolymerization of styrene with methyl methacrylate at 80°C in the presence of catalytic system tributylborane–p-quinone (1,4-naphthoquinone, duroquinone) has been studied. The copolymerization proceeds via the mechanism of the reversible inhibition. The number-average molecular weights of the copolymers linearly increase with progress in monomer conversion. The contribution of the “living” mechanism in the total process depends on the structure of the quinone. Reactivity ratios of the monomers differ from the values known for conventional radical polymerization. The experimental data of triad concentration and average composition correlate with theoretical value.     

Quantifying and Controlling the Composition and ‘Randomness’ Distributions of Random Copolymers

The effect of disparity in the reactivity ratios of monomer pairs on the composition distribution and microstructure of the resultant copolymer formed through free‐radical polymerization is quantified computationally. This correlation has been determined for the monomer pairs of styrene/methyl methacrylate and styrene/2‐vinyl pyridine for a variety of monomer feed ratios. These monomer pairs were chosen as they represent systems that have been utilized to experimentally examine the importance of copolymer architecture on its ability to compatibilize an immiscible polymer blend. Moreover, their respective random copolymers show conflicting results for this examination. The results of this work show that the difference in the reactivity ratios of styrene and 2‐vinyl pyridine copolymer (r₁ = 0.5, r₂ = 1.3) significantly broadens the composition and randomness distribution of the resultant copolymer. This breadth is not easily avoided as it evolves even in the early stages of the copolymerization. Conversely, for the styrene/methyl methacrylate pair, the reactivity ratios are similar (r₁ = 0.46, r₂ = 0.52) and this results in a copolymer with a narrow composition distribution and sequence distribution dispersion. Stopping the polymerization at early conversion further narrows both distributions. The presented results, therefore, provide fundamental information that must be considered when planning an experimental procedure to evaluate the relative importance of sequence distribution and composition distribution of a random on its application.     

Synthesis of Graft Polymers by Copolymerization of Macromonomer. III. Preparation and Copolymerization of Styrene-Terminated Poly(Oxyethylene) Macromonomer

Styrene-terminated poly(oxyethylene) macromonomers (SOE) with narrow molecular weight distribution and quantitative styrene monofunc-tionality were synthesized. In homopolymerization of SOE, conversion of monomer to polymer was shown to be low in spite of high consumption of the vinyl groups of the SOE molecules. Free-radical copolymer-ization of the macromonomer with methyl methacrylate and styrene occurred smoothly, as opposed to homopolymerization. Cumulative copolymer composition and total conversion were determined from the conversions of macromonomer and comonomer (by weight changes) and by proton NMR of the copolymer. The monomer reactivity ratios were found to be r_a = 0.06 and r_b = 2.0 for the copolymerization of SOE macromonomer (a) with methyl methacrylate (b). In this case the macromonomer exhibited considerably lower reactivity than predicted from its low molecular weight model compound. The monomer reactivity ratios estimated for SOE and styrene were r_a = 0.86 and r_b = 1.20. The reactivity of SOE was comparable to, but somewhat lower than, styrene. The graft copolymers were used as activators in the halogen displacement reaction, and it was found that their catalytic activity depends on copolymer composition and chemical structure.     

Formation of hyperbranched polymers in atom transfer radical copolymerization of MMA and DVB

Hyperbranched poly(methyl methacrylate)s (HPMMAs) have been successfully prepared by atom transfer radical copolymerization of MMA and divinylbenzene (DVB). Kinetic study shows complete consumption of the initiator in 0.5 h, and relatively low polymerization rate when DVB content in the feed was high. By analyzing MALDI-TOF spectra of the resulting copolymers, the linear A _n B* (n = 0, 1, 2, 3) oligomers were formed in 0.5 h of polymerization, and then the oligomers reacted each other to form dimers, further reactions produced HPMMA. The SEC and NMR spectroscopies were used to trace the polymerization, and the results demonstrate that small amount of the branching reactions occur in the initial polymerization, and the branched polymers are significantly generated past a certain conversion depending upon the feed ratios. Raising the content of DVB in the monomer mixture can increase the pendent vinyl groups of the linear oligo-inimers, leading to gelation at low MMA conversion.     

Organotin polymers—VIII. Binary and ternary copolymerizations of triphenyltin methacrylate with arylonitrile,styrene, N-vinyl pyrrolidone and n-butyl methacrylate

Copolymerizations involving triphenyltin methacrylate (PTMA) were carried out in solution at 70° in the presence of a free radical initiator; the copolymer compositions were determined from tin analyses. The monomer reactivity ratios for the copolymerizations of PTMA with acrylonitrile, styrene, and N-vinyl pyrrolidone were: r₁ = 0.69, r₂ = 0.16; r₁ = 0.76, r₂ = 0.47, and r₁ = 1.22, r₂ = 0.36, respectively. The sequence distribution of the alternation diads for the systems were calculated at various feed compositions. Ternary copolymerization of PTMA-acrylonitrile-butyl methacrylate was studied; the variation of terpolymer composition with conversion fit satisfactorily the experimental results. Ternary azeotropy for PTMA-acrylonitrile-styrene system was verified experimentally.     

Reactivity ratios in conventional and nickel-mediated radical copolymerization of methyl methacrylate and functionalized methacrylate monomers

Copolymerization of an excess of methyl methacrylate (MMA) relative to 2-hydroxyethyl methacrylate (HEMA) was carried out in toluene at 80 °C according to both conventional and controlled Ni-mediated radical polymerizations. Reactivity ratios were derived from the copolymerization kinetics using the Jaacks method for MMA and integrated conversion equation for HEMA (r_MMA = 0.62 ± 0.04; r_HEMA = 2.03 ± 0.74). Poly(ethylene glycol) α-methyl ether, ω-methacrylate (PEGMA, M_n = 475 g mol⁻¹) was substituted for HEMA in the copolymerization experiments and reactivity ratios were also determined (r_MMA = 0.75 ± 0.07; r_PEGMA ∼ 1.33). Both the functionalized comonomers were consumed more rapidly than MMA indicating the preferred formation of heterogeneous bottle-brush copolymer structures with bristles constituted by the hydrophilic (macro)monomers. Reactivity ratios for nickel-mediated living radical polymerization were comparable with those obtained by conventional free radical copolymerization. Interactions between functional monomers and the catalyst (NiBr₂(PPh₃)₂) were observed by ¹H NMR spectroscopy.     

Monomer Reactivity Ratios for the Copolymerization of p-lsopropylstyrene with Styrene and Methyl Methacrylate

Abstract

The monomer reactivity ratios for the copolymerizations of p-isopropylstyrene with styrene and with methyl methacrylate have been determined by the ionization chamber-vibrating reed electrometer radioactivity assay technique. The values from the differential form of the copolymerization equation are r₁ (styrene) = 1.22, r₂ (p-isopropylstyrene) = 0.89, and r₁ (methyl methacrylate) = 0.44, r₂ (p-isopropylstyrene) = 0.39. The values from the integrated form of the equation are r₁ (styrene) = 1.37 and r₂ = 0.99. These values indicate that, in the copolymerization of p-divinylbenzene (p-DVB) with styrene, the p-isopropylstyrene-like unit, formed from having the first vinyl group of p-DVB reacted, takes part in subsequent propagation reactions with styrene less readily than either styrene or p-DVB.     

Fluorescent polymer particles by emulsion and miniemulsion polymerization

We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, r_A), we show that the reactivity ratios with styrene (r_A = 0.71, r_B = 0.25) and butyl methacrylate (r_A = 0.87, r_B = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766–778, 2003     

The influence of molecular interactions on polymerization—IV: Copolymerization of 2-naphthyl methacrylate and methyl methacrylate in solvents with different dielectric constants

The copolymerization of 2-naphthyl methacrylate (2-NM) with methyl methacrylate (MMA) initiated by 2,2′-azoisobutyronitrile in carbon tetrachloride, chloroform, benzene, acetone and acetonitrile was investigated. The reactivity ratios determined by the methods of Fineman-Ross and Kelen-Tüdo&#x030B;s are: in carbon tetrachloride—r_2-NM = 2.46 ± 0.25, r_MMA = 0.61 ± 0.06; chloroform—r_2-NM = 2.71 ± 0.30, r_MMA = 0.60 ± 0.06; benzene—r_2-NM = 2.62 ± 0.44, r_MMA = 0.63 ± 0.11; acetone—r_2-NM = 4.13 ± 0.45, r_MMA = 0.60 ± 0.06 and acetonitrile—r_2-NM = 3.70 ± 0.30, r_MMA = 0.62 ± 0.05.The dependence of the reactivity ratios on the solvent is explained on the basis of formation of complexes between the electron-donating naphthalene rings and the electron-accepting methacrylic double bonds, as indicated by NMR studies.     

Radical copolymerization of acrylic monomers. IV. Effect of substituents on the radical polymerization and copolymerization of phenyl acrylates

The kinetics of radical polymerization of phenyl, ortho-chlorophenyl, and para-chlorophenyl acrylates, as well as their copolymerization with methyl methacrylate, have been studied dilatometrically. The results obtained indicate that the overall rate of polymerization is affected by the flexibility of the growing radicals. However, the copolymerization of these monomers with methyl methacrylate gives overall rates rather similar for all three systems, being fundamentally regulated by the formation of reversible π complexes between the donor aromatic rings and the acceptor methacrylic double bonds. Dilatometric methods for the study of the copolymerization reactions have been tested and the corresponding binary bonding frequencies B_ij and conversion factors K_ij have been calculated for the copolymerization of ortho- and para-chlorophenyl acrylates with methyl methacrylate.     

Vinylhydroquinone. III. Copolymerization of vinylhydroquinone and vinyl monomers by tri-n-butylborane

The copolymerization of vinylhydroquinone (VHQ) and vinyl monomers, e.g., methyl methacrylate (MMA), 4-vinyl-pyridine (4VP), acrylamide (AA), and vinyl acetate (VAc), by tri-n-butylborane (TBB) was investigated in cyclohexanone at 30°C under nitrogen. VHQ is assumed to copolymerize with MMA, 4VP, and AA by vinyl polymerization. The following monomer reactivity ratios were obtained (VHQ = M₂): for MMA/VHQ/TBB, r₁ = 0.62, r₂ = 0.17; for 4VP/VHQ/TBB, r₁ = 0.57, r₂ = 0.05; for AA/VHQ/TBB, r₁ = 0.35, r₂ = 0.08. The Q and e values of VHQ were estimated on the basis of these reactivity ratios as Q = 1.4 and e = ?;1.1, which are similar to those of styrene. This suggests that VHQ behaves like styrene rather than as an inhibitor in the TBB-initiated copolymerization. No homopolymerization was observed either under nitrogen or in the presence of oxygen. The reaction mechanism is discussed.     

Reversible addition-fragmentation chain transfer polymerization of methacrylate, acrylate and styrene monomers in 1-alkyl-3-methylimidazolium hexfluorophosphate

1-alkyl-3-methylimidazolium hexfluorophosphate ([C_x][PF₆], where x=4, 6-8) is used as solvent for the polymerisation of methyl methacrylate, methyl acrylate and styrene by the reversible addition-fragmentation chain transfer process. In the case of styrene, the insolubility of the polymer in ionic liquid stops the polymerization at an early stage. The acrylate and methacrylate polymerizations lead to products with molecular weights close to the theoretical ones and polydispersity indexes lower than 1.3. The polymerizations are shown to be living by chain extension of the products formed in ionic liquid. In the case of the methyl methacrylate, the kinetics of the polymerizations are followed and the molecular weight of the polymer is shown to increase linearly with the conversion, as expected for a living polymerization.     

Graft copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate onto hide powder

Graft copolymerization of 2-hydroxyethyl methacrylate(HEMA) and mixtures of HEMA with methyl methacrylate (MMA) onto hide powder was attempted using ceric ammonium nitrate as initiator, with a view to optimize the conditions for graft copolymerization. Percent grafting and grafting efficiency were calculated for various variables such as monomer concentration, initator concentration and mole ratio of HEMA to MMA. R_p, R_g and R_h (rates of polymerization, grafting and homopolymerization respectively) were also evaluated. It was observed that R_p increased linearly with increasing concentration of MMA except at very low concentrations of the monomer. An explanation is given for the effect of variables on extent of grafting and grafting efficiency.     

Copolymerization of sodium 2-crylamido-2-methylpropanesulfonate with sodium acrylate in concentrated aqueous solutions

The kinetic features of potassium persulfate-initiated homogeneous radical copolymerization of sodium 2-acrylamido-2-methylpropanesulfonate (M₁) with sodium acrylate (M₂) in concentrated aqueous solutions and NaCl aqueous solutions at pH 9 and T = 60°C have been studied. The initial rate of copolymerization increases with the concentration of each monomer, the total concentration of comonomers (M₁ + M₂), the concentration of initiator, and the concentration of NaCl and shows an extreme change with an increase in the content of M₂ in the initial monomer mixture. The molecular mass of the copolymer shows an extreme dependence on the content of M₂ in the initial monomer mixture; it drops with an increase in the concentration of NaCl and remains unchanged with conversion. For copolymerization in water and 2 M NaCl, r ₂ > r ₁. The number of M₂ units in the copolymer does not change with conversion and increases on addition of NaCl owing to a gain in r ₂.