Polymerisation radiochimique de l''acide methacrylique en solution

The polymerization of methacrylic acid was investigated in various solvents under the action of gamma-rays. It was found that, as in the case of acrylic acid, solvents could be divided into groups according to the observed effects. The addition of methanol or dioxane up to 50 per cent does not significantly alter the polymerization rate. These two solvents do not dissociate the plurimolecular aggregates of methacrylic acid, the presence of which is demonstrated by the high viscosity of the medium. In the presence of either toluene or n-hexane, the rate gradually decreases and the aggregates are dissociated. Chloroform and CCl₄ also dissociate the aggregates but lead to acceleration of the reaction. This effect which was not observed with acrylic acid presumably results from an energy transfer process. The polymerization of methacrylic acid in bulk and in solution has a very small overall activation energy, 1·0–1·5 kcal/mole between 16 and 60°. All conversion curves are linear in contrast to the case of acrylic acid where auto-accelerated conversion curves were observed in most mixtures. A comparison of these results shows that the initial rates of polymerization of acrylic acid follow relationships similar to those observed for methacrylic acid except for the chlorinated solvents. It is concluded that the molecular aggregates produce the same influence on the polymerization of methacrylic acid as on the initial stages of the reaction for acrylic acid, but the “matrix effect” of poly(acrylic acid) does not appear in the case of poly(methacrylic acid).     

Influence of the solvents on the γ-ray polymerization of acrylic acid. I.

Bulk polymerization of acrylic acid is controlled by linear plurimolecular H-bonded aggregates of the monomer. It is proved that it is not the precipitating medium that is responsible for the accelerated rate of the polymerization, but the presence of the H-bonded plurimolecular aggregates. It has been shown that the presence of the previously formed polymer is important, as it gives a matrix effect which allows the monomer aggregated to be stabilized by associating with the polymer. In polymerizing acrylic acid solutions, two types of solvents have been characterized: first, the polar solvents which do not destroy the H-bonded aggregates up to high dilutions. Then, in the presence of hydrocarbons or chlorinated solvents, 10–20% of the solvents dissociate the aggregates. A very striking parallelism is observed between the polymerization kinetics and the associated form of the monomer.     

Polymerisation de l'acide methacrylique en masse et en solution

In spite of the fact that the bulk polymerization of methacrylic acid proceeds under precipitating conditions, all conversion curves are linear and start from the origin. The overall activation energy of the gamma ray initiated reaction is very small: 1.3 kcal/mol. Methanol and water are solvents for the polymer but also form monomer-solvent complexes through H-bonds. It was found that, over a limited concentration range in these solvents, the reaction becomes auto-accelerating both in precipitating and homogeneous reaction media. Non-polar solvents (hydrocarbons) lead to a significant reduction in the polymerization rate but this effect is not as pronounced as for acrylic acid. Chlorinated derivatives reduce the polymerization rate of acrylic acid to the same extent as hydrocarbons but, for methacrylic acid, chlorinated derivatives lead to sensitization. By analogy with earlier results for acrylic acid, it is assumed that the auto-acceleration observed in water and methanol solutions is caused by a “matrix effect”. In bulk, the monomer undoubtly also associates with the polymer but, in view of the bulky methyl groups, the regularly oriented structure which favours propagation presumably never arises. The very small activation energy of the polymerization suggests that chain termination requires a significant activation energy. The mechanism of this process is not clear.     

Copolymerization parameters of methyl methacrylate and acrylic acid

The relative reactivity of acrylic acid is known to be influenced by the polymerization medium. Nonetheless, the more commonly used reactivity ratios do not show this dependence because they were calculated from low-conversion polymerizations. We have studied the copolymerization of acrylic acid and methyl methacrylate in a number of non-hydrogen-bonding and hydrogen-bonding solvents. We found that the acrylic acid fraction in the copolymer was larger when copolymerized in a non-hydrogen-bonding medium and that the methyl methacrylate fraction was larger when copolymerized in a hydrogen-bonding medium. The precise reactivity ratios were reported when toluene, benzene, isopentyl, acetate, ethyl acetate, methyl formate, and tert-butyl alcohol were used as the polymerization medium. The values were obtained by chromatographic analysis of residual monomer, followed by computation based on the nonlinear, least-squares technique of Tidwell and Mortimer.     

Influence de la temperature sur les associations moleculaires et sur la polymerisation de l'acide acrylique en solution

Infra-red spectra of pure acrylic acid and solutions of monomer in toluene indicate that increasing the temperature from 20 to 60° displaces the equilibrium of H-bonded species from cyclic dimer to open oligomer. Viscosity measurements on the same solutions confirm this conclusion. In methanol solutions. alcohol-alcohol and alcohol-acid associations are found together with the acid-acid associations and the interpretation of the results is extremely difficult. Polymerization kinetics are directly influenced by the shift of association equilibria. In hexane, an increase in temperature results in a sudden increase in reaction rate as the linear oligomeric structures appear in the solution. In methanol increase in temperature reduces the kinetic anomalies observed at 20 and the polymerization no longer exhibits any stereospecificity. At the same time, a chain transfer process sets in. These various results confirm the earlier assumption of an assisted propagation step occurring in auto-associated aggregates of acrylic acid.     

Influence of the solvents on the γ-ray polymerization of acrylic acid. II.

The presence of plurimolecular H-bonded aggregates in the acrylic acid allows the polymer to involve some stereoregular sequences. This effect is made easier when some polymer is already formed in the reacting medium: the aggregates are stabilized by hydrogen bonds with the polymer which gives rise to a matrix effect. Two groups of solvents have been characterized by examination of the monomer's association forms in solution. In a first group of solvents (methanol–dioxan–water), the aggregates are maintained and reinforced; in the second one, acrylic acid exists only as cyclic dimers (hydrocarbons–chlorinated solvents). The difference between the association forms of the monomer involves some important modifications on the kinetics of polymerization and the structure of the obtained polymers. In the solvents of the first group, the obtained polymers are crystallizable and may involve syndiotactic sequences, while in the presence of the solvents of the second group no crystallization or stereoregularity of the polymer can occur. A very close correlation is thus found between the aggregated structure of the monomer, the polymerization kinetics, and the structure of the polymers.     

Polymerisation radiochimique de l'acide acrylique en solution dans l'alcool isopropylique et le dimethylformamide

The radiation-induced polymerization of acrylic acid in isopropyl alcohol and dimethylformamide solutions was investigated between?196°and40°. Mixtures which form glasses at low temperatures exhibit a maximum in the rate of polymerization at 30° and 50° above the glass transition temperature (T_g). The difference between the most favourable temperature for polymerization and T_g is larger than in systems studied previously. This fact could be due to the presence of H-bonded aggregates.The study of the polymerization of acrylic acid in dimethylformamide solution at 20° led to a correlation between this reaction and the presence of plurimolecular aggregates. The very high polymerization rate and the syndiotacticity of the resulting poly(acrylic acid) confirm the earlier assumption of a favourable orientation for propagation of the molecules of acrylic acid in these aggregates.     

Reactivities of carboxylic acid vinyl monomers differentiated by the aggregation forms and their simple molecular orbital interpretation

Plasma-exposed solution polymerizations of carboxylic acid vinyl monomers [methacrylic acid (MAA) and acrylic acid (AA)] in carbonyl solvents were found to be highly efficient, particularly in high-temperature postpolymerizations. Thermal polymerizations in these solvents were also accelerated to a considerable extent. Obviously the carbonyl solvents and/or the increased temperature caused the monomer aggregates to accelerate the rate of polymerization. The molecular orbital features of the simple models of monomer aggregates, that is, the monomeric form, singly hydrogen bonded open-dimer and doubly hydrogen bonded cyclicdimer of MAA and AA, supported by the CNDO/2 method, were capable of distinguishing the variations in the reactivities of the aggregates; the open-dimer was shown to be responsible for the enhanced reactivities under the abovementioned conditions.     

Effects of solvent in photo-induced graft copolymerization of vinyl monomers on cellulose

The effects of swelling of the sample and polymerization solvents were studied for photo-induced graft copolymerization of vinyl monomers on cellulose. The graft copolymerization of methyl methacrylate (MMA) was activated by swelling of the sample or organic solvent-water solutions within a certain range of their concentrations. Though each organic solvent gave a maximum in per cent grafting and the number of grafts at about 25 vol-% concentration, the initiation reaction scarcely took place at 100% concentration; thus, the solvent itself is considered to have a negative effect. The solvents used in the experiments were all hydrophilic, such as methanol, acetone, and dioxane. The average molecular weight of the grafted PMMA differed in each solvent, indicating a different characteristic effect of solvent on the growing grafted polymer radicals. The presence of ferric ion as a sensitizer stimulated further the contributions of the sample swelling and the organic solvents to the copolymerization reaction. A similar effect was observed for styrene as for MMA, but not for acrylic acid and methacrylic acid.     

Influence des associations moleculaires sur la copolymerisation de l'acide acrylique avec l'acide methacrylique et avec l'acrylate de methyle

The copolymerization of acrylic acid with methacrylic acid in bulk is investigated at 40 and 60°. It is confirmed that a “matrix effect” occurs only for high contents of acrylic acid. The critical concentration beyond which the matrix effect disappears is shifted towards lower acrylic acid contents for higher temperatures. The copolymer composition is independent of temperature. The copolymerization of acrylic acid with methyl acrylate is investigated in a mixture which determines an “exaltation of the matrix effect” in the homopolymerization of acrylic acid (molar fractions: m_Monomers = 0.34; m_n-Hexane = 0.52; m_Methanol = 0.14). The resulting copolymers are found to contain a much larger fraction of acrylic acid residues than the copolymers formed in bulk or in toluene or DMF solutions.     

Frontal Polymerization of Deep Eutectic Solvents Composed of Acrylic and Methacrylic Acids

Frontal polymerization of deep eutectic solvents (DESs) made with acrylic or methacrylic acid as the monomer and hydrogen bond donor was studied. Fronts with acrylic acid and choline chloride propagated more uniformly than with pure acrylic acid, so an exploration into how the DES affected frontal polymerization was performed. The hydrogen bond acceptor of the DES was replaced by several analogs to determine the effect on the DES front behavior. The analogs used were talc, DMSO, lauric acid, and stearic acid, which acted as a heat sink, inert diluent, hydrogen bonding diluent, and inert phase change material, respectively. None of the methacrylic acid‐analog systems were able to sustain a front. While the acrylic acid‐analog systems did sustain a front (with the exception of stearic acid), none of the fronts replicated the acrylic acid DES behavior. The acrylic acid–talc sample behaved more violently—like pure acrylic acid polymerization—than the acrylic acid DES, and the DMSO and lauric acid samples produced slower fronts than that of the acrylic acid DES. We propose that the reactivity of the acrylic acid and methacrylic acid is enhanced in the DES. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 4046–4050     

Free-radical polymerization in micellar media: Effect of microenvironment

A micellar polymerization process has been used to prepare polyacrylamide or poly(acrylic acid) hydrophobically modified with low amounts (1–5 mol%) of an N-alkyl- or N-alkylarylacrylamide. The effect of the initial monomer segregation on the copolymer microstructure and the copolymerization mechanism has been investigated. This method leads generally to multiblock copolymers in which the number and length of the hydrophobic blocks vary with the initial number of hydrophobes per micelle. Interestingly, the copolymerization of acrylamide with disubstituted acrylamides leads to homogeneous samples with an average copolymer composition independent of the degree of conversion, in contrast to what is observed with monosubstituted acrylamides for which a drift in composition is observed. The difference in polarity between the bulk phase and the micellar phase is responsible for this behavior. This microenvironment effect modifies the reactivity ratios of those hydrophobes capable of forming hydrogen bonds, whereas the reactivity of the other hydrophobes remains unaffected.     

Surface modification of polyamide-6: graft copolymerization of vinyl monomers onto polyamide-6 and thermal analysis of the graft copolymers

Graft copolymerization of vinyl monomers onto polyamide-6 using radical initiation has been investigated. Two monomers were used: methacrylic acid and acrylic acid. The initiators selected included hydrogen peroxide, benzoyl peroxide and azobisisobutyronitrile. The extent of graft copolymerization depends on the concentrations and identity of the initiator and monomer and the time and temperature of the reaction. The graft copolymers were not soluble in solvents that will dissolve the starting material; definitive proof for the formation of the graft copolymers was obtained from infrared spectroscopy. Thermogravimetric analysis was performed on the graft copolymers and it was found that the presence of the acid invariably accelerated the degradation of the polyamide. © 1998 John Wiley & Sons, Ltd.     

Modification and Application of Poly(Ethylene Terephethalate) Nonwoven Fiber Using Octadecyl Acrylate and Acrylic Acid as Oil Sorbers

Three series of crosslinked octadecyl acrylate and acrylic acid copolymers were prepared through suspension copolymerization based on acrylic acid content (10, 30, 50%wt. ratio). Divinyl benzene (DVB) was used as a crosslinker with different weight ratios (1, 4 and 10%). Isopropyl alcohol or dioctyl phthalate and methyl benzoate were used as two different reaction solvents in the presence of ABIN as initiator. The prepared crosslinked copolymers were characterized by SEM, TGA and FTIR spectroscopic analyses. The prepared polymers were coated onto poly(ethylene terephethalate) nonwoven fiber (NWPET). The effect of copolymerization feed composition, crosslinker wt% and reaction media or solvent on swelling properties of crosslinked polymers were studied through the oil absorption tests in toluene and 10% of diluted crude oil with toluene. It was noticed that the maximum swelling of crosslinked copolymers was increased from 30 to 100 g/g after grafting of copolymers onto NWPET.     

SYNTHESIS OF POLYACRYLAMIDE WITH PENDANT POLY(BUTYL ACRYLATE) CHAINS USING THE MACROMER TECHNIQUE AND STUDIES ON THEIR PROPERTIES

INTRODUCTIONSince Milkovich and Chiang[1] developed a method of preparing copolymers with uniform side chains by usingthe macromer technique, the synthesis of copolymers with uniform side chains from different macromers hasbeen studied extensively. Milkovich et al. reported the synthesis of polystyrene macromer through termination ofliving polystyrene anions with methacryloyl chloride and its copolymerization with butyl acrylate to formthermoplastic elastomer[2]. Rempp[3] obtained polyoxy…     

Self-propagating frontal copolymerization

The application of self-propagating frontal polymerization (FP) to synthesize copolymers has been investigated. Frontal copolymerizations of methyl methacrylate and methacrylic acid (MMA–MAA), acrylic acid and methacrylic acid (AA–MAA), and styrene and methacrylic acid (STY–MAA) with benzoyl peroxide (BPO) as initiator have been performed. The measured front velocities have been compared with the results of a suitably developed model. This is based on the pseudokinetic approach, accounts for the depropagation reaction, and is fully predictive; i.e., it does not include any adjustable parameter (although one had to be used for the specific experimental setup used in this work). An explicit, simplified solution of the model has been obtained using the constant pattern approximation. The microstructures of copolymers produced in bulk and by FP have been analyzed by differential scanning calorimetry. Their comparison indicates that self-propagating frontal copolymerization provides a substantial improvement in the uniformity of the chain composition distribution. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1117–1126, 1998     

Alkali salts of (ω-sulphoxyalkyl)-acrylates and -methacrylates: Radical polymerization and copolymerization

A new preparation of alkali salts of (ω-sulphoxyalkyl)-acrylates and -methacrylates, by reaction of alkali salts of acrylic and methacrylic acids with cyclic sulphates, is described; spectral characterization of the products is described. The kinetics of the radical polymerization of sodium (2-sulphoxyethyl)methacrylate (SSEM) were studied; monomer reactivity ratios for copolymerization with methacrylic acid were: r₁ = 1.1 ± 0.15 and r₂ = 0.73 ± 0.05. Dark electrical surface conductivity of some homopolymers and copolymers with methacrylic acid was found to be 10⁴–10¹¹$\text{Ω}{}^{\mathrm{?1}}$, depending on relative humidity.     

Statistical radical copolymerization of styrene and methyl methacrylate in a room temperature ionic liquid

Use of a room temperature ionic liquid as the medium for conventional free radical copolymerization of styrene and methyl methacrylate resulted in reactivity ratios that were significantly different from those obtained in conventional organic solvents or in bulk, demonstrating that polymerization in this alternative medium offers potential to create copolymers having new monomer sequences.     

Copolymerization of acrylic and methacrylic acids with N-vinylpyrrolidone

The copolymerization of an acidic monomer (acrylic or methacrylic acid) and a basic monomer (N-vinylpyrrolidone) (NVP) is investigated. Various physical measurements revealed a strong molecular interaction between the two monomers. However, the resulting association complex does not seem to control the copolymerization. A slight solvent effect is observed with dimethylformamide for the acrylic acid-NVP system. Methacrylic acid appears to be much more reactive than acrylic acid in its copolymerization with NVP. The results obtained with methacrylic acid-NVP system conflict with earlier published results.     

Dimethyl 1-hexene-2,5-dicarboxylate,methyl methacrylate dimer,as polymerizable acrylic ester bearing bulky α-substituent

Dimethyl 1-hexene-2,5-dicarboxylate (MMAD), a methyl methacrylate dimer, which is an acrylic ester bearing a large α-substituent, was polymerized and copolymerized. During the bulk polymerization at room temperature, an ESR spectrum assigned to the propagating radical was observed. MMAD which polymerized much slower than methyl methacrylate (MMA) was less reactive in copolymerization than MMA. These findings may exemplify that slow propagation concomitant with termination suppressed with steric hindrance could lead to polymer formation of MMAD. Thermogravimetric analysis of poly(MMAD) exhibited that the degadation through depropagation was facilitated by the α-substituent. A relatively large chain transfer constant of MMAD in MMA polymerization, 9.8 × 10^?3, was evaluated consistent with a considerable decrease in the molecular weight of poly (MMA) in the presence of a small amount of MMAD.