The preparation of block copolymers of styrene and methacrylic acid

A new method of preparing block copolymers of styrene and methacrylic acid is described. It is based upon use of the anionically initiated “living chain” method to prepare block copolymers of styrene and methyl methacrylate, with subsequent hydrolysis of the methyl methacrylate block to methacrylic acid.     

Deformational,swelling, and potentiometric behavior of ionized gels of 2-hydroxyethyl methacrylate–methacrylic acid copolymers

The deformational, swelling, and potentiometric behavior of ionized water-swollen gels of 2-hydroxyethyl methacrylate (HEMA)–methacrylic acid (MA) copolymers used in biomedical and separation applications was investigated. With increasing degrees of neutralization α, the swelling degree strongly increases and the modulus G_s decreases. For the copolymers with MA content ? 30 mole-%, the dependence of G_s on α passes through a minimum. Comparison of the results with the modified theory of rubber elasticity shows that the decrease in G_s at low concentrations of charges on the chain is controlled mainly by the degree of swelling. At higher α, both the finite extensibility of network chains, caused by a high degree of swelling, and electrostatic interactions contribute to G_s. The dependence of the interaction parameter χ on the volume fraction of polymer in the gel, v₂, is independent of α and closely resembles the dependence obtained for other hydrophilic polymers.     

Preparation of block copolymers of styrene and methacrylic acid

A range of block copolymers of styrene and methacrylic acid has been prepared by the suspension method involving migration of a growing radical across a phase boundary. The way in which copolymer composition varies with change in the amount of the two monomers in the reaction mixture has been studied, and explanations are suggested to account for these variations. Two methods, involving calculation from solubility data and thermogravimetric analysis respectively, have been used to give an estimate of the length and composition of the blocks.     

Structure-mechanical property relationships in ethylene methacrylic acid copolymers and their salts

A dynamic mechanical study has been made of an ethylenemethacrylic acid copolymer containing 4.1 mole per cent of methacrylic acid units and its sodium, lithium and calcium salts. On the basis of the results and related physical chemical studies it is proposed that the structures of the ionized copolymers consist of three distinct phases—a crystalline polyethylene phase, an amorphous polyethylene phase, and an ionic phase consisting of ionic domains. It is further proposed that the unionized acid copolymer consists of two phases—a crystalline polyethylene phase and an amorphous phase consisting of polyethylene crosslined with hydrogen bonded, carboxylic acid dimers.     

Characterization of styrene/methacrylic acid copolymers by 2D-NMR spectroscopy

Styrene/methacrylic acid copolymers were prepared by free-radical photopolymerization using the uranyl nitrate ion as the initiator. The copolymer composition was determined from ¹H-NMR spectroscopy. The comonomer reactivity ratios determined using Kelen Tudos and nonlinear error in variable methods (EVM) are r_m = 0.61 ± 0.05 and r_s = 0.14± 0.07. The broad and overlapping ¹H-NMR spectrum was assigned using the help of 2D TOCSY and NOESY experiments. These methods were used to ascertain the various geminal, vicinal, and spatial couplings between the protons. The methyl and methine protons also show configurational and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2444–2453, 2001     

Syntheses and characterization of starch-poly(methacrylic acid) graft copolymers

Methacrylic acid (MA) was graft polymerized onto starch using Ce⁴⁺ initiator in aqueous medium. The dependence of grafting on the reaction variables, such as monomer and initiator concentration and time and temperature, was studied in detail. Acid hydrolysis and infrared (IR) spectroscopy were used for the confirmation of graft copolymer formation. Further, a representative graft copolymer was characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The solubility/swellability and the gelatinization characteristics of the copolymers are also reported. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1399–1403, 1997     

Ethylene–methacrylic acid copolymers as stress whitening suppressants in polypropylenes

Impact-modified polypropylenes were prepared by incorporating copolymers of ethylenemethacrylic acid (E-MAA) with different cations (zinc or sodium) and varying degrees of neutralization. These blends gave low stress whitening on impact. This phenomenon was due to the unique morphology of the blend. It was found that unneutralized acid copolymer and the zinc ionomer formed chainlike structures in the polypropylene matrix. These uniform chains crisscrossed the polypropylene matrix providing impact strength to the matrix. The matrix deformed on impact by the shear yielding mechanism, thus suppressing stress whitening. The impact modifier in the matrix did not form micro crazes in the matrix but formed several layers of crisscrossing chains. On the other hand, the sodium ionomer did not form chainlike structures. The impact modifier was dispersed evenly in the matrix. This type of morphology resulted in a higher degree of stress whitening. The failure on impact was due to crazing and not by shear yielding. This size of the impact modifier in the polypropylene matrix varied significantly depending on the melt processing equipment used. The dependence of polymer alloy mechanical properties on the composition has been studied to help in ionomer comparison.     

Statistics of the formation of ester on syndiotactic methacrylic anhydride-methacrylic acid copolymers

Summary The mode of ring opening during methanolysis of syndiotactic methacrylic anhydride-methacrylic acid copolymers has been studied by statistical calculation, Monte Carlo Simulation,and H-NMR. Significant deviations from random ring opening are found, indicating that the nature of the monomer unit adjacent to the anhydride ring may exert an influence.     

13C NMR spectral assignments of methacrylic acid/acrylonitrile statistical copolymers

Copolymerization of methacrylic acid (M) and acrylonitrile (A) in bulk at 60°C gives a statistical copolymer. Through the use of ¹H, ¹³C, DEPT and twodimensional NMR techniques, the observed resonances in the NMR spectra of these copolymers can be assigned, and thus provide detailed information about the microstructure of the polymer at the diad, triad and tetrad levels. Configurational effects have also been shown to play an important role, although in all cases the chemical shift differences resulting from configurational variation are smaller than those resulting from sequence variation.     

用甲基丙烯酸改善PMMA光纤芯材的耐热性

用甲基丙烯酸(MAA)改性PMMA,使其维卡软化点提高了20~23℃,透光率未降低。     

A molecular model for viscometric and potentiometric irreversibility in isotactic poly(methacrylic acid)

The energies of the accessible dyad states in isotactic poly(methacrylic acid) (PMAAI) are shown to be sensitive to the rotational states of the methyl and adjoining methylene groups, the individual hydrogen atoms of which must interdigitate to give low energy interactions across the dyad. Thus all-trans and all-trans-gauche sequences have low energies but mixed states are of high energy and interconversion takes place sequentially. The potentiometric irreversibility is traced to the inability of all-trans states to convert to trans-gauche states to promote ionization. The intervention of gauche-gauche states at intervals into trans-trans dyad sequences is of accessible energy and accounts for the observed irreversibility in viscometric titrations during which the chain dimension passes through a maximum on addition of alkali. The instability of PMAAI solutions at low degrees of ionization is also discussed.     

Radical polymerization of methacrylic acid in the presence of copolymers of 4-vinylpyridine in methanol

Summary Random copolymers of 4-vinylpyridine (4VP) with styrene and with acrylamide were effective to enhance the overall rate of radical polymerization of methacrylic acid(MA) in methanol. The rate maximum did not occur at the equimolar ratio of 4VP unit/MA but it depended on the copolymer composition.     

The electrochemical behaviour of silver sulphide in sulphuric acid solutions

The electrochemical behaviour of synthetic silver sulphide (acanthite) electrodes in sulphuric acid solutions has been investigated using several techniques including cyclic voltammetry, anodic polarization and constant potential experiments. Under anodic polarization the dissolution has been attributed to the reaction Ag₂S=2Ag⁺+S+2e which occurs in two sequential, single electron transfer steps. A kinetic model for this stepwise anodic dissolution process at lower overpotential, where the current is a function of potential, is provided. At high dissolution rates (i.e. high currents) the slightly soluble silver sulphate salt is formed on the surface due to the saturation of the electrolyte near the Ag₂S interface. This observation is supported by the influence of electrolyte composition on the cyclic voltammetry and the polarization curve. A paralinear film growth model has been found to describe the formation and growth of the silver sulphate product layer indicating an initial region of parabolic kinetics which gradually changes to linear kinetics as the rate of film dissolution approaches that of film formation.     

The anodic behaviour of Ebonex® in oxalic acid solutions

A study of the oxidation of aqueous solutions of oxalic acid in various supporting electrolytes, at an Ebonex^® anode is reported. From data obtained by cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, controlled potential coulometry and gas chramatography it has been shown that oxalic acid oxidation at an Ebonex^® anode, does not proceed, to any significant extent. Data collected using different electrolytes showed that sulphuric acid supported higher current densities at similar electrode potentials. Ebonex^® is essentially a selective oxygen evolver and is thus a suitable anode for the electroreduction of oxalic acid to glyoxylic acid in an undivided cell. The behaviour of a platinized titanium anode is also reported and this material has similar electrochemical characteristics to Ebonex^® in aqueous oxalic acid solutions.     

Fourier transform ir studies of the degradation of polyacrylonitrile copolymers—II: Acrylonitrile/methacrylic acid copolymers

The results of a Fourier transform IR study of the degradation of an acrylonitrile copolymer containing approx. 4 wt% of methacrylic acid, at 130°C under a reduced pressure of 5 × 10^?2 Torr, are presented. A mechanism is proposed for the degradation that is consistent with the IR spectral evidence. Additionally, we have determined from our experimental results that methacrylic acid is incorporated into the cyclized degraded structure and that, on average, three to four acrylonitrile acids are cyclized for each acid initiation.     

Anodic behaviour of pyrite in acid solutions

In acid solution, pyrite gives reproducible anodic current3v?oltage curves with Tafel slopes 95 ± 10 mV. There is no influence of pyrite semiconducting properties on the kinetics of the anode process. This process, as determined by coulometry at constant potential and product analysis, is a combination of the reactions

and

The sulphate route dominates over the potential range accessible at ambient temperature, and the sulphate yield increases linearly with potential. Data from other sources suggest that sulphate yield at fixed potential may be independent of temperature. Evidence from studies of the electrochemical behaviour of sulphur and its compounds leads to the conclusion that elemental sulphur is not an intermediate in the sulphate route. A mechanism for sulphate formation involving adsorbed oxygen-containing intermediates is postulated and the kinetics analysed under Temkin adsorption conditions. The Tafel slope and pH dependence suggest that the second electron transfer step is rate-determining.     

Photografting of methacrylic acid onto HDPE initiated by acetaldehyde in aqueous solutions

Acetaldehyde could act as a very effective photoinitiator for water‐borne photografting. The photografting of methacrylic acid (MAA) onto polyethylene initiated by acetaldehyde in aqueous solutions was reported. Acetaldehyde had higher photoinitiation efficiency than acetone and formaldehyde. The extent of grafting varied with the acetaldehyde content in the solution and it showed the maximum when the content of acetaldehyde was about 10 w/w %. The extent of grafting firstly increased with the increase of monomer concentration till 2 mol/L and then kept constant or slightly decreased. ATR‐FTIR characterizations of the grafted samples proved the successful grafting of MAA onto PE, and the calculated carbonyl indexes were in accord with the results obtained by the gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The difference in the photoinitiation efficiencies of acetaldehyde, acetone and formaldehyde was discussed through their differences in the n‐π* transitions in water and the photoinitiation process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of the carboxylate group distribution on potentiometric titration of acrylamide-acrylic acid copolymers

Summary the potentiometric behavior of acrylamide-acrylic acid copolymers is discussed as a function of their method of preparation: base hydrolysis of polyacrylamide or radical copolymerization. The values of pK₀ (the intrinsic pK at zero degree of ionization) and the variations of pK_a versus the ionization degree are found to depend on the origin of the polymers and such differences are qualitatively attributed to significant discrepancies in the carboxylate group distribution.     

Synthesis and characterization of copolymers of carbazolylalkyl(meth)acrylates and methacrylic acid

Summary The copolymerization of 2-(9-carbazolyl)ethylmethacrylate, 3-(9-carbazolyl)propyl-2-methacrylate and 2-(9-carbazolyl)ethylacrylate with methacrylic acid has been studied obtaining the reactivity ratios of the monomers in benzene. For the estimation of molar masses and copolymer compositions esterification of the copolymers has been performed. A thermal study of the obtained copolymers related to the carbazolylalkyl(meth)acrylate content has been carried out taking into account several theories predicting the dependence of the glass transition temperature on the copolymers composition. The copolymers in which the molar fraction of methacrylic acid did not exceed ca. 65 mol % exhibit glass transition. Glass transition temperatures increase with the increase of molar fraction of methacrylic acid. Received: 7 August 2000/Revised version: 19 September 2000/Accepted: 22 December 2000     

Adiabatic compressibility of polyelectrolytes in aqueous solutions: Poly(methacrylic acid)

The adiabatic compressibility of dilute aqueous solutions of methacrylic acid, poly-(methacrylic acid), and three poly(sodium methacrylates) obtained by neutralizing the polyacid with sodium hydroxide to different extents were determined from soundvelocity and density data. The ultrasonic velocity at 25°C. was measured by employing a precision ultrasonic interferometer, and the density was measured with Ostwald-type pycnometers. The plots of the decrease of compressibility per unit concentration, (β₁ ? β)/c versus c shows that there is a marked difference between the curves of monomer and of polymer solutions. In case of the monomer there is a proportional decrease with increase in concentration, whereas in polymer in the dilute region (0.1?0.5g./dl.) the curve rises sharply, then shows down, and finally approaches a constant value at comparatively higher concentrations. The nature and number of the free counterions and the shape and the concentration of the polymer molecules are responsible for the compressibility of polymer solutions. However, the contribution of the size and shape and concentration of the polymer seem to be less than that of the nature and number of the counterions. The apparent molal volume ΦV₂ and apparent molal compressibility ΦK₂ for polymer repeat units show a sharp decrease with increase in concentration and finally attain a constant value at higher concentrations; this has been explained by the fact that in the dilute region the polymer, being extended by coulombic repulsion between similar charges situated on the side chain, enhances the formation of water clusters around it, and the free counterions are solvated, leading to a decrease to these values. The number of free counterions proportionately increases with concentration, causing a proportional decrease of the ΦV₂ and ΦK₂ values, until the concentration reaches a definite stage, above which the so-called condensation of ions occurs, and the number of free counterions does not increase further at higher concentrations.