Further discussion of the cyclopolymerization of acrylic anhydride in terms of ring size control

Radical cyclopolymerization of acrylic anhydride (AA) was conducted under various polymerization conditions to yield highly cyclized polymer, and the content of the five-membered ring of cyclic poly-AA obtained was examined in detail. Five-membered ring formation was favored with increased solvent polarity, raised polymerization temperature, and decreased monomer concentration; the ring size of the cyclic structure could be controlled freely by choosing appropriate polymerization conditions. In addition to these results, the rate of polymerization and the molecular weight of the polymer were reduced under polymerization conditions where the five-membered ring formation was favored. Finally, a mechanistic discussion is given in order to interpret these results; a reaction scheme for propagation based on polymerization equilibrium is proposed.     

Alternating copolymerization of α-methylstyrene and maleic anhydride

Alternating copolymers of α-methylstyrene (α-MeSt) and maleic anhydride (MAn) were prepared by free-radical-initiated polymerization in bulk, benzene, or butanone as solvents. By applying the generalized model described by Shirota and co-workers, the reactivity ratios k_1c/k₁₂ and k_2c/k₂₁ were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration. From the equation R_p = R_p(f) + R_p(CT) were calculated R_p(f) and R_p(CT), and it was found that in benzene the reaction proceeds predominantly by the addition of CT-complex monomers, while in butanone, cross propagation of free monomers predominates. Termination occurs predominantly by homotermination of α-MeSt macro free radicals, k_t22, although the cross termination k_t21 is also operative.     

Polymers from renewable resources. II. A study in the radio chemical grafting of poly(styrene‐alt‐maleic anhydride) onto cellulose extracted from pine needles

A binary mixture of styrene and maleic anhydride has been graft copolymerized onto cellulose extracted from Pinus roxburghii needles. The reaction was initiated with gamma rays in air by the simultaneous irradiation method. Graft copolymerization was studied under optimum conditions of total dose of radiation, amount of water, and molar concentration previously worked out for grafting styrene onto cellulose. Percentage of total conversion (Pg), grafting efficiency (%), percentage of grafting (Pg), and rates of polymerization (R_p), grafting (R_g), and homopolymerization (R_h) have been determined as a function of maleic anhydride concentration. The high degree of kinetic regularity and the linear dependence of the rate of polymerization on maleic anhydride concentration, along with the low and nearly constant rate of homopolymerization suggest that the monomers first form a complexomer which then polymerizes to form grafted chains with an alternating sequence. Grafting parameters and reaction rates achieve maximum values when the molar ratio of styrene to maleic anhydride is 1 : 1. Further evidence for the alternating monomer sequence is obtained from quantitatively evaluating the composition of the grafted chains from the FT‐IR spectra, in which the ratio of anhydride absorbance to aromatic (CC) absorbance for the stretching bands assigned to the grafted monomers remained constant and independent of the feed ratio of maleic anhydride to styrene. Thermal behaviour of the graft copolymers revealed that all graft copolymers exhibit single stage decomposition with characteristic transitions at 161–165°C and 290–300°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1763–1769, 1999     

The influence of steric factors on the mechanism of copolymerization of phenylvinyl alkyl ethers and maleic anhydride

By assuming that the initial rate of copolymerization (R_p) of phenylvinyl alkyl ether (I) and maleic anhydride (MAn) equals the sum of the rate of polymerization of free monomers R_p(f) and CT complex monomers R_p(CT) the reactivity ratios k_1c/k₁₂ and k_2c/k₂₁ were calculated for copolymerization of I(R = Me, n-Pr, iso-Pr, and sec-Bu) and MAn from the change of copolymerization rate with monomer feed at a constant total monomer concentration. From the equation R_p = R_p(f) + R_p(CT) were calculated R_p(f) and R_p(CT) by applying the generalized model described by Shirota and coworkers and it was found that the participation of CT complex monomers increases with an increase in total monomer concentration in the feed. It was also found that the degree of CT complex monomer participation depends largely on the steric factors. In the copolymerization of I which contains bulky isopropyl or sec-butyl group even in the dilute solutions, copolymerization proceeds by the addition of CT complex monomers.     

Studies of the polymerization of diallyl compounds. VII. Kinetics of the polymerization of diallyl esters of aliphatic dicarboxylic acids

Radical polymerization studies on diallyl oxalate (DAO), diallyl malonate (DAM), diallyl succinate (DASu), diallyl adipate (DAA), and diallyl sebacate (DAS) have been conducted kinetically from the standpoint of cyclopolymerization. Benzoyl peroxide was employed as the initiator. The initial overall rate of polymerization, R_p was not proportional to the square root or the first power of the initiator concentration, [I]. But R_p/[I]^1/2 and [I]^1/2 bore a linear relationship, provided the monomer concentration was kept constant. The residual unsaturation of the polymers decreased with decreasing monomer concentration. The ratio of the rate constant of the unimolecular cyclization reaction to that of the bimolecular propagation reaction of the uncyclized radical, K_c, was evaluated from the above relationship between the residual unsaturation and the monomer concentration at 60°C. The K_c values obtained were 3.6, 3.2, 2.8, 2.5, and 1.2 mole/l. for DAO, DAM, DASu, DAA, and DAS, respectively. The overall activation energies of polymerization were found to be 21.1 (DAO), 24.2 (DAM), 21.7 (DASu), 22.0 (DAA), and 22.2 (DAS) kcal/mole.     

Effects of macromolecular matrix on the process of radical polymerization of ionizable monomers

Radical polymerization of methacrylic acid (MAA) and acrylic acid (AA) in the presence of a positively charged macromolecular matrix was studied. In the presence of a matrix, the rates of polymerization were remarkably increased, especially in high pH region. This suggests that electrostatic interaction between the macromolecular matrix and the growing chains and/or the monomer molecules plays an important role in the process of polymerization reaction. The kinetic orders were greatly influenced by the relative matrix concentration (PC) as follows: for (PC)₀ > [M]₀, R_p = k[M]^0.9 [PC]_0.3 [I]^0.8≤ [M]₀ R_p = k[M]^0.3[PC]⁰[I]^0,8 where [M] and [I] are monomer and initiator concentration, respectively, and k is a constant. The mechanism of the interaction of matrix with monomer and/or growing chains in the process of the propagation is discussed. The complex formed in the matrix polymerization could be easily made into fiber by spinning.     

Kinetics of polymerization of acrylic acid initiated by Mn3+–isobutyric acid redox system. II

The kinetics of redox -initiated polymerization of acrylic acid (AA) by the systerm Mn³⁺-isobutyric acid (IBA) in sulfuric acid was studied in the temperature range of 35–50°C. The overall rates of polymerization (R_p), disappearance of manganic ion (?R_m), and degree of polymerization (X _n), were measured with variation in [monomer], [Mn³⁺], [IBA], H⁺, μ, [Mn²⁺], and temperature. The polymerization is initiated by the organic free radical that develops from the Mn³⁺-isobutyric acid oxidation reaction. Two types of termination reactions, one by the metal ion (Mn³⁺) and the other by the MN³⁺-isobutyric acid complex are proposed to explain the kinetic results. The various rate parameters were evaluated an discussed.     

Radiation-induced polymerization of acrylic acid in aqueous solution

Aqueous acrylic acid in the presence of cupric chloride has been subjected to γ-irradiation under various reaction conditions and the molecular weights of the resultant poly(acrylic acid) measured. The results, taken in conjunction with previous findings on the dependence of the rate of polymerization on intensity, monomer concentration, and cupric chloride concentration, indicate chain termination solely by cupric ion (rate constant k_tCu) and chain transfer to polymer (rate constant kf). Values have been obtained for k_tCu/k_p, k_f/k_p and G(radical) of acrylic acid. On the basis of these data a theoretical chain-length distribution has been derived which agrees well with distribution measured by gel-permeation chromatography.     

Vinyl polymerization initiated by peroxydiphosphate. XII. Polymerization of acrylamide and acrylic acid by peroxydiphosphate–sodium thiosulfate redox system

The aqueous polymerization of acrylic acid and acrylamide initiated by peroxydiphosphate–sodium thiosulfate redox system was investigated within the temperature range of 25–35°C. The rates of polymerization were measured at different concentrations of oxidant, activator and monomer. The monomer and the initiator exponents were evaluated to be 1.12 and 0.51. The rate of polymerization decreases with increasing thiosulfate concentration. On the basis of the experimental observation of the dependence of the rate of polymerization, R_p, on various variables, a suitable kinetic scheme has been proposed and the rate parameters have been evaluated.     

Alternating copolymerization of β-methylstyrene and maleic anhydride

Alternating copolymers of β-methylstyrene and maleic anhydride were prepared by free-radical-initiated polymerization in bulk and in toluene as a solvent. The reactivity ratios k_1c/k₁₂ and k_2c/k₂₁ were calculated from the change of copolymerization rate with a monomer feed at a constant total monomer concentration according to the generalized model of Shirota and coworkers. From the equation R_p = R_p(f) + R_p(CT) were calculated R_p(f) and R_p(CT), and it was found that in toluene the copolymerization proceeds predominantly by the addition of CT-complex monomers. Termination occurs predominantly by homotermination of β-methyl-styrene macro free radicals, k_t22, but the cross termination k_t21 is also operative.     

Studies of the polymerization of diallyl compounds. XXVI. Enhanced polymerizability by the hydroxyl group in the polymerization of diallyl hydroxydicarboxylates

In order to elucidate the effect of the hydroxyl group on the polymerization of diallyl hydroxydicarboxylates, we investigated in detail the radical polymerizations of diallyl succinate (DASu), diallyl malate (DAMa), and diallyl tartrate (DATa), each of which have similar structure differing only in the number of hydroxyl groups present. The rate of polymerization (R_p) was quite enhanced in the order DASu < DAMa < DATa, in accord with the increase in the number of hydroxyl groups within a monomer unit. The enhanced ability of the allylic monomer radical to reinitiate chain growth was also in the same order, as was clear from the dependence of R_p on the initiator concentration. The dependence of the residual unsaturation of the polymer on the monomer concentration in the polymerizations of DAMa and DATa was abnormal in terms of cyclopolymerization. These results are discussed in connection with the formation of the intermolecular hydrogen bond through the hydroxyl groups.     

Effect of high pressures on the cyclopolymerization of acrylic anhydride

The effect of pressures up to 4000 atm on the free-radical cyclopolymerization of acrylic anhydride in solution has been investigated. Both the molecular weight and degre of cyclization of the polymer are increased by pressure. The rate of polymerization at first decreases with increasing pressure, but above 2500 atm a normal acceleration occurs.     

The dependence of cyclopolymerizability of acrylic and methacrylic anhydrides on various conditions: New interpretation of temperature dependency of cyclization constant in radical cyclopolymerization of nonconjugated dienes

The cyclization constant K_c in the radical cyclopolymerization of acrylic and methacrylic anhydrides was evaluated in detail under various conditions. No linear relationship between in K_c and 1/T was observed; cyclization was acceleratively enhanced at elevated temperatures. The K_c values also increased with decreased monomer concentration and increased solvent polarity. These increasing dependencies of K_c are ascribed to the increased significance of depropagation, demonstrating a new interpretation of the temperature dependence of the cyclization constant in the radical cyclopolymerization of nonconjugated dienes.     

Controlled polymerization of acrylic acid under 60Co irradiation in the presence of dibenzyl trithiocarbonate

The polymerization of acrylic acid (AA) was performed under ⁶⁰Co irradiation in the presence of dibenzyl trithiocarbonate at room temperature, and well‐defined poly(acrylic acid) (PAA) with a low polydispersity index was successfully prepared. The gel permeation chromatographic and ¹H NMR data showed that this polymerization displays living free‐radical polymerization characteristics: a narrow molecular weight distribution (M_w/M_n = 1.07–1.22), controlled molecular weight, and constant chain‐radical concentration during the polymerization. Using PAA? S? C(?S)? S? PAA as an initiator, the extension reaction of PAA with fresh AA was carried out under ⁶⁰Co irradiation, and the results indicated that this extension polymerization displayed controlled polymerization behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3934–3939, 2001     

Homogeneous hydrogels made with acrylic acid,acrylamide and chemically functionalized carbon nanotubes

Carbon nanotubes (CNTs) chemically functionalized were used to synthesize a series of novel nanocomposite hydrogels by in situ polymerization with acrylic acid (AA) and acrylamide (AM). A novel strategy was developed to prepare these hydrogels. CNTs were functionalized following a three-step chemical procedure: (i) purified carbon nanotubes (CNTs_p) were partially surface oxidized to obtain CNTs with hydroxyl, carbonyl and carboxyl groups on their sidewalls (CNTs_oxi), (ii) CNTs_oxi were reacted with oxalyl chloride to obtain CNTs functionalized with acyl chloride groups (CNTs_OCl), and (iii) CNTs_OCl were reacted with acrylic acid (AA). The product, AA modified CNTs_OCl (CNTs_OCl-AA) was used to prepare the (CNTs_OCl-AA-AM) nanocomposite hydrogels, where anhydride groups were tethered to the surface of the CNTs_OCl-AA. The swelling process in water was evaluated as a consequence of the anhydride group hydrolysis, which broke some chemical links between CNTs_OCl-AA and crosslinked AA-AM network. Equilibrium-swelling values of all hydrogels increased as the content of AA increased and were larger for AA-AM hydrogels than for CNTs_OCl-AA-AM nanocomposite hydrogels. Young’s moduli of CNTs_OCl-AA-AM nanocomposite hydrogels prepared with 1 or 2?wt.% AA, reached larger values than those measured for AA-AM hydrogels. This tendency was reversed when the AA content was raised to 3?wt.%.     

Cyanoxyl‐mediated free‐radical polymerization of acrylic acid: Its scope and limitations

This work examines the scope and limitations of the cyanoxyl (^·OC?N)‐mediated free‐radical polymerization of acrylic acid (AA) with respect to the criteria of livingness. Cyanoxyl persistent radicals were generated in situ through the reaction between arenediazonium salts (X? C₆H₄N?N^⊕BF, where X is H, OCH₃, Cl, or NO₂) and sodium cyanate (NaOCN). This article thoroughly discusses the role played by such oxygen‐centered radicals in the polymerization process; it particularly focuses on the influence of the concentration and nature of the diazonium salt, the solvent, and the temperature on features such as the variations of ln([M]₀/[M]) versus time (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration), the number‐average molar mass versus conversion, and the polydispersity versus conversion in cyanoxyl‐mediated free‐radical polymerizations of AA. Cyanoxyl‐terminated samples were used as macroinitiators for the polymerization of methyl methacrylate to generate poly(acrylic acid)‐b‐poly(methyl methacrylate) block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 519–533, 2005     

Polymerization of acrylamide and acrylic acid photoinitiated by diazidotetramminecobalt (III) azide

The kinetics of polymerization of acrylamide and acrylic acid in aqueous solution photoinitiated by the complex, diazidotetramminecobalt(III) was systematically studied at 35°C and pH = 3. Monochromatic radiation at γ = 365, 405, and 435 mμ was employed. The kinetics of polymerization were followed by measurements of the rates of monomer disappearance (bromometrically) and complex disappearance (spectrophotometrically) and the chainlengths of the polymers formed (viscometrically). The dependences of the rate of polymerization on variables like light intensity, light absorption by the complex, wavelength, monomer concentration, and hydrogen ion concentration were studied. The rates of polymerization of acrylamide and acrylic acid were found to be propertional to the square of the monomer concentration and to the first power of light absorption fraction k_e and light intensity I. A kinetic scheme is proposed in the light of experimental results involving (1) a primary photochemical act of excitation of the complex, followed by the dark reaction of electron transfer within the complex producing the azide radical; (2) initiation of polymerization by the azide radical; (3) termination of the chain process by the complex molecule.     

Kinetics of polyelectrolyte network formation in free-radical copolymerization of acrylic acid and bisacrylamide

Recently, a research/development program has been initiated to investigate the kinetics of synthesis, characterization and applications of polyelectrolyte networks. The research on crosslinking involves both theoretical development and experimentation. Herein, is provided a summary of this work. In the experimental polymerization done to date, acrylic acid (AA)/N.N'-methylenebisacrylamide (BAM) was studied in considerable detail. The polymerization conditions were: temperature, 50°C; initial monomer concentration, 5 wt%, of which 1.0 mol% is BAM; K₂S₂O₈(KPS) as the initiator, 10⁻³ mol/L; pH range, 1 − 13; sodium chloride concentrations up to 3.1 mol/L. Measurements included: monomer conversion, polymer composition, sol/gel fraction, swelling ratio, and the densities of primary cyclization, secondary cyclization and crosslinking. It was found that the effect of polymerization parameters on the resulting polymer network microstructure was dramatic, and in particular, the pH and ionic strength of the reaction medium were important parameters. In the theoretical studies, the Tobita-Hamielec kinetic gelation model was extended to incorporate the concept of ion pair interaction and the divinyl loop formation. The system was treated as a multi-component polymerization of acrylic acid, acrylate ion, acrylate ion pair and bisacrylamide. The model permits one to investigate the development of the crosslinking density distribution among primary polymer chains during the course of polymerization as a function of pH and ionic strength.     

Alternating copolymerization of ethylene with maleic anhydride

The copolymerization of ethylene with maleic anhydride was carried out with γ-radiation and a radical initiator, i.e., 2,2′-azobisisobutyronitrile and diisopropyl peroxydicarbonate under pressure at various reaction conditions. The homopolymerization of neither monomer was observed in this system. In the γ-ray-initiated copolymerization the G value (polymerized monomer molecules per 100 e.v.) was shown to be between 10³ and 10⁴. It was found that the dose rate exponent of the rate is approximately unity, and the rate is proportional to the amount of ethylene monomer. Apparent activation energies of 1.8 and 27.5 kcal./mole were obtained for γ-ray-initiated and AIBN-initiated copolymerization, respectively. Since the composition of copolymer is independent of monomer molar ratio and the molar ratio of ethylene to maleic anhydride in the polymer is approximately unity, the monomer reactivity ratios were obtained as r_E ? 0 and r_M ? 0 for γ-ray-initiated polymerization at 40°C. Alternating copolymerization was, therefore, concluded to occur. Infrared analysis of the copolymer is almost consistent with this. The copolymer in the solid state is amorphous. It is soluble in water, cyclohexane, and dimethylformamide and insoluble in lower alcohols, ether, and aromatic hydrocarbons. The aqueous solution of polymer gave a strong acid.     

Free radical copolymerization in the presence of lewis acids. I. Alternating copolymerization of vinyl acetate with acrylic acid in the presence of GeCl4 and BCl3

Alternating copolymers of vinyl acetate (VAC) and acrylic acid (AA) were obtained by free radical polymerization in the presence of GeCl₄ and BCl₃. For the GeCl₄ system, the reaction rate was proportional to [initiator]^1/2. Optimum rate was obtained when the molar ratio of the monomers was 1:1. The chain transfer agent CCl₄ had no effect on the reaction. By means of ultra-violet spectra analysis, it was concluded that both VAC and AA formed complexes with GeCl₄. ESR analysis gave us the information that salt complexed acrylic acid radical had greater cationic characteristics than uncomplexed radical. Thus the nature of alternation may be due to both complexed AA radical and activated monomer complexes.