A study of the ring size in the copolymer of divinyl ether and maleic anhydride by H-NMR spectroscopy

The well-known alternating 1:2 cyclocopolymer of divinyl ether (DVE) and maleic anhydride (MA) possesses a wide spectrum of biological activities, including antitumor. Recent research on the structure of a variety of cyclopolymers has raised a question about the ring size of this cyclocopolymer. In this article we report on an extensive spectroscopic study of its structure. By use of deuterated monomers the H-NMR peaks at δ 2.31, 3.47, 4.06, and 4.49 ppm with an area ratio of 2:1:1:1 were assigned to the hydrogens of methylenes, methines on the backbone anhydride unit, methines on the ring anhydride unit, and methines adjacent to oxygen on the cyclic ether ring, respectively. By examination of the possible isomeric structures of the bicyclic ring, the splitting of each peak group was further assigned for cis and trans disubstitutions on the anhydride unit. The splitting pattern from the 300-MHz NMR spectrum of the DVE-2,3-dideuteriomaleic anhydride (DMA) copolymer confirmed the unsymmetrical ring structure. ¹³C-NMR spectra were consistent with the conclusion from the H-NMR spectra. A chair-form, six-membered ring with predominantly trans geometry in the anhydride ring was assigned to the structure of DVE–MA copolymer. On the basis of little or no change in the ¹³C-NMR spectra of the copolymers prepared at different temperatures it was concluded that there was no significant change in structure with temperature. This led to the assignment of the energetically favored, six-membered ring structure to the copolymer prepared under these conditions. A mechanism for cyclocopolymerization, based on the HOMO–LUMO interaction of the comonomers and the intramolecular radical addition on the preoriented double bond, was proposed. This mechanism leads to the formation of the six-membered ring structure of the copolymer as the only product. A ¹³C-NMR study of the structure of the copolymer prepared in chloroform by Kunitake and Tsukino is being published as a companion article.     

Characterization of chloroprene and maleic anhydride copolymer by 13C-NMR spectroscopy and pyrolysis GC/MS

The radical copolymerizations of chloroprene (CP) and maleic anhydride (MAH) were carried out with AIBN in 1,4-dioxane at 60°C. The monomer reactivity ratios were estimated as r₁ (CP) = 0.38 and r₂ (MAH) = 0.07. Microstructures in the copolymer of chloroprene (CP) and maleic anhydride (MAH) were investigated by 75.4 MHz ¹³C-and 300 MHz ¹H-NMR spectroscopies. Resonances were assigned to the monomer sequence dyads CC, CM, and MC (C = chloroprene, M = maleic anhydride). Well resolved fine structure in the ¹³C-NMR spectra showed that 1,2- and 3,4-structural chloroprene units were negligible in the copolymer. The pyrolysis characterization of the copolymer was also investigated by the pyrolysis gas chromatography mass spectrometry (GC/MS). The fragments of CP and MAH monomers and CP-MAH hybrid dimer, CO, and CO₂ were identified after pyrolysis of the copolymer. © 1994 John Wiley & Sons, Inc.     

Copolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride and terpolymerization with styrene as the third component

Copolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride was carried out. The monomer reactivity ratio was determined to be r₁ = 0.18, r₂ ～ 0 in terminal model and r₁ = 0.015, r₁′ = 0.224, r₂′ = r₂′ = 0 in the penultimate model. Calculations of run number, linkage probabilities, and number-average chain length in the terminal model and comparison of n (mole ratio of each monomer unit content in copolymer) in each model with the experimental value was made. From these results, the obtained polymer was confirmed to be alternating. Terpolymerization of 4-methyl-1,3-dioxene-4 with maleic anhydride and styrene was also carried out. The agreement of the experimental value (titration by indicator or electroconductivity) of maleic anhydride content with the theoretical value confirms that the terpolymer has a DMS triad sequence.     

Copolymers containing alternating sequences of nucleic acid base pairs. III. Spectroscopic studies

A study was conducted of the complementary base pair interactions between various pairs of electron-donor monomers, electron-acceptor monomers, homopolymers and alternating copolymers selected from the following group: ( 1 ) 9-(2-vinyloxyethyl)adenine; ( 2 ) 1-(2-vinyloxyethyl)thymine; ( 3 ) 1-(2-vinyloxyethyl)cytosine; ( 4 ) 9-(2-maleimidoethyl)adenine; ( 5 ) 6-chloro-9-(2-maleimidoethyl)purine; ( 6 ) 1-(2-maleimidoethyl)thymine; ( 7 ) 1-(2-maleimidoethyl)cytosine; ( 8 ) homopolymer of ( 4 ); ( 9 ) homopolymer of ( 6 ); ( 10 ) alternating copolymer of ( 2 ) and maleic anhydride; ( 11 ) alternating copolymer of ( 2 ) and ( 5 ); and ( 12 ) alternating copolymer of ( 2 ) and ( 4 ). By ¹H-NMR, in CDCL₃, the base pair interactions between ( 1 ) and ( 2 ) were shown to be hydrogen bonding, the extent of which was shown by a calculated binding constant, K = 61.81 L/mol. The nature of this interaction was conformed by IR. Neither monomer pairs ( 1 )/( 2 ) nor ( 4 )/( 6 ) exhibited hydrogen bonding in DMSO-d₆. However, hydrogen bonding interaction was observed for DMSO-d₆ solutions of homopolymers ( 8 ) and ( 9 ) and for alternating copolymer ( 12 ). On the basis of an upfield chemical shift of the 2- and 8-aromatic protons of ademine of ( 1 ) in D₂O, a partial overlap stacking interaction is proposed. No charge-transfer interactions could be observed by UV between donor-acceptor monomer pairs.     

Bioengineering functional copolymers. III. Synthesis of biocompatible poly[(N‐isopropylacrylamide‐co‐maleic anhydride)‐g‐poly(ethylene oxide)]/poly(ethylene imine) macrocomplexes and their thermostabilization effect on the activity of the enzyme penicillin G acylase

Stimuli‐responsive poly[(N‐isopropylacrylamide‐co‐maleic anhydride)‐g‐poly(ethylene oxide)]/poly(ethylene imine) macrobranched macrocomplexes were synthesized by (1) the radical copolymerization of N‐isopropylacrylamide and maleic anhydride with α,α′‐azobisisobutyronitrile as an initiator in 1,4‐dioxane at 65 °C under a nitrogen atmosphere, (2) the polyesterification (grafting) of prepared poly(N‐isopropylacrylamide‐co‐maleic anhydride) containing less than 20 mol % anhydride units with α‐hydroxy‐ω‐methoxy‐poly(ethylene oxide)s having different number‐average molecular weights (M_n = 4000, 10,000, or 20,000), and (3) the incorporation of macrobranched copolymers with poly(ethylene imine) (M_n = 60,000). The composition and structure of the synthesized copolymer systems were determined by Fourier transform infrared, ¹H and ¹³C NMR spectroscopy, and chemical and elemental analyses. The important properties of the copolymer systems (e.g., the viscosity, thermal and pH sensitivities, and lower critical solution temperature behavior) changed with increases in the molecular weight, composition, and length of the macrobranched hydrophobic domains. These copolymers with reactive anhydride and carboxylic groups were used for the stabilization of penicillin G acylase (PGA). The conjugation of the enzyme with the copolymers significantly increased the thermal stability of PGA (three times at 45 °C and two times at 65 °C). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1580–1593, 2003     

Structure study of the furan–maleic anhydride copolymer

A structural study of furan–maleic anhydride copolymer (F–MAH) was undertaken to confirm its alternating nature and to determine its microstructure. The spectral properties of a model compound representing the alternating repeat unit, 2-(2-tetrahydrofuranyl)succinic anhydride, were compared with those of F–MAH. Their infrared (IR), ¹H, and ¹³C nuclear magnetic resonance (NMR) spectra (after compensating for the absence of the olefinic double bond) were in good agreement with those of the copolymer. Furthermore, the observed splitting in the ¹H- and ¹³C-NMR spectra of F–MAH were assigned to cis–trans linkages on both the F and MAH units, with cis linkage being favored on both units, especially the former. The structure of 2,5-dimethylfuran (DMeF)–MAH copolymer is similar to that of F–MAH copolymer, except that the preference of cis linkages is less pronounced. The structure of 2-methylfuran (MF)–MAH copolymer is a complex structure with numerous 2,3-furandiyl units. A mechanistic study was undertaken to elucidate the roles of F–MAH Diels–Alder adduct, and the charge-transfer (CT) complex in the radical initiated copolymerization. The adduct reverted substantially to monomers under the reaction conditions; but, the amount of adduct remaining at equilibrium was quite appreciable; therefore, its participation could be ruled out on this basis alone. However, on polymerizing the adduct in the presence of F-d₄, the latter was incorporated into the copolymer to an extent indicative of free monomer exchange. Therefore, the adduct cannot be directly involved in the polymerization.     

Investigations on the dissociation behavior of hydrolyzed alternating copolymers of maleic anhydride and alkenes: 13C-NMR spectra and potentiometric titrations

The pK_a values of the succinic acid moieties of hydrolyzed alternating ethene- and isobutene-maleic anhydride copolymers were determined in D₂O. The pD-dependence on the ¹³C chemical shift of selected signals was analyzed for these copolymers. Four different pK_as were determined for the copolymer with ethene due to the existence of both the erythro- and threo-configuration of the succinic acid moiety: pK_01,erythro = 4.2, pK_0.1,threo = 4.1, pK_02,erythro = 6.1, pK_02,threo = 6.8. The isobutene-maleic anhydride copolymer contains only threo-units. Therefore, only two dissociation steps with pK₀₁ = 3.0 and pK₀₂ = 8.7 were observed for the hydrolyzed form. © 1996 John Wiley & Sons, Inc.     

A study of the relative reactivity of maleic anhydride and some maleimides in free radical copolymerization and terpolymerization

Composition data for the free radical copolymerization of maleic anhydride with N-phenylmaleimide in toluene at 60°C have been obtained. Relative reactivity ratios in terminal and penultimate models using nonlinear least-squares optimization routine have been determined. The standard error was found to be somewhat smaller in the penultimate model, but is still larger than the uncertainty estimated for the copolymer composition. Terpolymers of maleic anhydride and styrene with maleimide, N-butylmaleimide, N-phenylmaleimide, and N-carbamylmaleimide were obtained. On the basis of analysis of the product composition at various monomer feeds the relative reactivity of maleic anhydride and maleimides in these reactions is compared and the influence of the structure of thesemonomers on the rate of some chain growth reactions is discussed.     

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.     

Characterization of the ground state pyrene complex in ethylene-propylene copolymer solutions

Pyrene-labeled functionalized ethylene-propylene (EP) copolymer was prepared by grafting 1-pyrenebutyrylhydrazine onto EP copolymer through maleic anhydride pendants. The EP copolymer contained 60 mol % ethylene; its weight-average molecular weight (M^w) was 148,000. The pyrene-labeled amide functionalized EP copolymer, PA-EP(60/40), was made to simulate the amine functionalized EP copolymers that are commonly used as dispersant additives in motor oils. UV absorption spectra, fluorescence emission and excitation spectra, and fluorescence decay profiles of the pyrene were studied to determine the copolymer conformation and dynamics in methylcyclohexane and tetrahydrofuran (THF). The pyrene fluorescence characteristics of PA-EP(60/40) were highly dependent on the solvent. The dependence of fluorescence emission intensity on the excitation wavelength was large in methylcyclohexane and moderate in THF. A frequency shift of about 2 nm was observed between the excitation spectrum obtained with the emission line at 377 nm and that at 550 nm in the methylcyclohexane solutions, but no shift was found in the corresponding tetrahydrofuran solutions. The ratios of the preexponential factors (a₂₁/a₂₂) of the excimer decays obtained in both methylcyclohexane and THF solutions were different from ?1.0. However, the deviation of the excimer formation process from the Birks scheme is small in THF but large in methylcyclohexane. In addition, the Huggins constants obtained from intrinsic viscosity measurements of the PA-EP(60/40) copolymer solutions suggest that copolymer aggregation occurs in methylcyclohexane but not in THF. H-bonding between two pyrene-containing pendants is apparently the main driving force for the formation of the ground state pyrene complex. THF is found to be effective in inhibiting the H-bonding formation. © 1995 John Wiley & Sons, Inc.     

Preparation and structural characterization of poly(4-vinylphenylacetate-co-maleic anhydride)

Poly(4-vinylphenylacetate-co-maleic anhydride) was synthesized by free-radical initiation to yield a 1:1 copolymer over a 0.2-0.8 mole fraction range of monomer feed in maleic anhydride. Evidence of 1:1 charge transfer complex between 4-vinylphenylacetate and maleic anhydride was obtained in the UV region at 355 nm. The ¹³C NMR chemical shifts and ¹H NMR integration data indicate that poly(4-vinylphenylacetate-co-maleic anhydride) has an alternating and stereoregular structure. The molecular weight of poly(4-vinylphenylacetate-co-maleic anhydride) was controlled by using specific solvents and initiator concentrations.     

Structure of poly(maleic anhydride)

The bulk polymerization of maleic anhydride initiated with acylperoxides, di-tert-butyl peroxide, AIBN, or pyridine proceeds with evolution of CO₂. The amount of CO₂ generated depends on the nature and the concentration of the initiator. With peroxide initiators, less than 5% of the polymerized maleic anhydride is decarboxylated. ¹H-NMR spectra, obtained on the benzoyl peroxide-initiated polymer and its methyl ester, are consistent with the unrearranged poly(maleic anhydride) structure and rule out the polycyclopentanone structure proposed by Braun and co-workers. Base-initiated polymaleic anhydride is substantially decarboxylated, and the resulting polymer has anhydride and carboxyl groups. Elemental analyses and ¹H-NMR spectra obtained on the pyridine-initiated polymer and its methyl ester refute both the cis-poly(vinylene ketoanhydride) structure suggested by Schopov and the polycylopentanone structure proposed by Braun and co-workers.     

Copolymerization between Nonconjugated Bicyclic Dienes and Maleic Anhydride

Abstract

Alternating copolymers of maleic anhydride and 5-ethylidene-, 5-methylene-, and 5-vinylbicyclo(2.2.1)-2-heptene were synthesized and found to contain the comonomers in a 1:1 ratio. Evidence is presented which supports a bicyclic structure which incorporates maleic anhydride as part of a six- or seven-membered ring in the repeat unit.     

Surface modification of fine colloidal silica with copolymer silane-coupling agents composed of maleic anhydride

The reactivity of copolymer silane composed of maleic anhydride in the modification of fine colloidal silica was studied. The reaction of colloidal silica of 10 and 45-nm diameter with trimethoxysilyl-terminated poly(maleic anhydride-co-styrene) [P(MA-ST)] and poly(MA-co-methyl methacrylate) in tetrahydrofuran resulted in effective surface modification without particle aggregation. From the results that the reaction using the polystyrene silane of low molecular weight led to partial aggregation, it was suggested that the steric interaction between relatively rigid copolymer chains having a maleic anhydride moiety adsorbed on the silica prevented the aggregation in the reaction. The ²⁹Si cross-polarization magic-angle-spinning NMR spectra of P(MA-ST)-modified silica showed that the polymer silane was bound to the silica surface by the direct reaction with silica hydroxyl groups and via the polymerization. Received: 27 June 2001 Accepted: 6 September 2001     

Preliminary study of extractable protein binding using maleic anhydride copolymer

A preliminary study of using maleic anhydride copolymer for protein binding has been carried out.The polymeric films were prepared by compression of the purified resin and annealing the film to induce efficient back formation of the anhydride groups.The properties of the film surface were analyzed by attenuated total reflection Fourier transforms infrared spectroscopy and water contact angle measurements.The protein content was determined by Bradford assay.To obtain optimum conditions,immersion time for protein binding was examined.Results revealed that proteins can be successfully immobilized onto the film surface via covalent linkage.The efficiency of the covalent binding of the extractable protein to maleic anhydride-polyethylene film was estimated at 69.87μg/cm~2,although the film had low anhydride content(3%) on the surface.     

Grafting of maleic anhydride to n-eicosane

Maleic anhydride was grafted to the linear hydrocarbon, n-eicosane, at 165°C in the presence of the free radical initiator, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne. The anhydride has a low solubility in eicosane and a multiple addition procedure was adopted. Grafted product which separated from the reaction mixture was fractionated and analyzed. The fractions contained on average 2–5.5 anhydride units/eicosane residue. ¹H- and ¹³C-NMR studies show that the grafts consist of single succinic anhydride rings. At the concentrations of maleic anhydride chosen for homogeneous reaction ( < 0.02 M) and at 165°C, poly(maleic anhydride) is above its ceiling temperature, so that succinic anhydride radicals cannot add maleic anhydride to form polymer side chains. Instead, these radicals abstract hydrogen atoms to yield grafts consisting of single anhydride units.     

Polymerization initiated by the charge-transfer complex of styrene and maleic anhydride in the presence of cumene and of cumene and liquid sulfur dioxide

A polymerization was induced with a charge-transfer type of complex consisting of styrene and maleic anhydride in the presence a solvent such as ethyl benzene, cumene, or p-cymene. No polymer was obtained either when the solvent was missing from the polymerization system or when benzene, toluene, or xylene, which are relatively stable to hydrogen abstraction, was added to the polymerization system. An effective initiation, however, took place when cumene or p-cymene, each of which has a labile hydrogen on an α carbon, was added. On the basis of elementary analysis and infrared spectroscopy the formation of copolymer containing substantially equimolar amounts of styrene and maleic anhydride was ascertained. This polymerization was inhibited by the addition of DPPH, suggesting that the system styrene–maleic anhydride–cumene functions much as a conventional free-radical initiator. On the other hand, when a solution of cumene and liquid sulfur dioxide was added to the polymerization system, polystyrene was obtained. This polymerization was inhibited by the addition of a base such as dimethyl-formamide or dimethyl sulfoxide, indicating that the polymerization proceeds through carbonium ion intermediates. The addition of ethyl benzene or of p-cymene brought about the same result as cumene. It is conceivable that the polymerization is induced by the abstraction of hydrogen attached at the α position of cumene by means of the charge-transfer complex of styrene and maleic anhydride.     

Thermodynamic study of deformation of crosslinked ethylene–propylene copolymer

The thermodynamics of deformation of ethylene–propylene copolymer crosslinked by dicumyl peroxide with addition of sulfur or maleic anhydride has been studied. Both the entropic (f_S) and energetic (f_U) components have been studied at elongations α up to 65%. It was found that the course of f_U/f, where f is equilibrium stress, in dependence on α agrees with the determined difference in both chemical and physical bonds.     

The Diels-Alder reaction between substituted 6,6-dimethyl-2-vinylnorpinenes and maleic anhydride

Cycloaddition of substituted 6,6-dimethyl-2-vinylnorpinenes with maleic anhydride occursvia the attack of a dienophile on diene from the less hindered side of the bicyclic fragment. IR, UV, CD, and¹H NMR spectra of adducts have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1546–1548, August, 1995.The authors are grateful to I. E. Ismaev for recording several¹H NMR spectra.     

Stereochemical applications of mass spectrometry. II—Chemical ionization mass spectra of isomeric dicarboxylic acids and derivatives

The H₂ and CH₄, chemical ionization mass spectra of the cis dicarboxylic acids, maleic and citraconic acid, show much more extensive loss of H₂O from [MH]⁺ than the trans isomers, fumaric acid and mesaconic acid. Similarly, esters of maleic acid show a much more facile loss of ROH (R=alkyl or phenyl) from [MH]⁺ than do esters of fumaric acid. Similar differences are observed in the chemical ionization mass spectra of the isomeric phthalic and isophthalic acids and derivatives, where the ortho isomers show more extensive fragmentation of [MH]⁺ than the meta isomers. The facile fragmentation of [MH]⁺ for the cis and ortho isomers is attributed to ROH elimination involving interaction between the two carboxylate functions and forming the stable cyclic anhydride structure for the fragment ion. By contrast ROH elimination from [MH]⁺ for the trans and metu isomers requires a symmetry-forbidden [1,3]-H migration in the carboxyl protonated species and cannot lead to the cyclic anhydride structure. The chemical ionization mass spectra of cis and trans cyclohexane-1,2-dicarboxylic acids are essentially identical and show extensive fragmentation of the [IMH]⁺ ion. Experiments using deuterium labelling show extensive carboxyl group interactions for both isomers. The chemical ionization mass spectra of maleanilic and phthalanilic acids and of the related anhydrides and imides also are reported, as are the electron impact mass spectra of diphenyl maleate, diphenyl fumarate, diphenyl phthalate, maleanilic acid and phthalanilic acid.