Radical polymerization of itaconic anhydride and reactions of the resulting polymers with amines and alcohols

Itaconic anhydride was polymerized in the presence of a radical initiator under various conditions. The bulk polymerization at 75°C yielded polymer with molecular weight of more than 20000. The reactions of the resulting polymer with water and alcohols gave poly(itaconic acid) and its esters, respectively. The polymers prepared by such reactions were found to have similar thermal properties to those prepared by homopolymerizations of the respective itaconic acid derivatives. Poly(N-substituted itaconomic acid)s, which are difficult to obtain by direct polymerization of their monomers, were prepared by the reactions of poly(itacononic anhydride) with amines. Copolymerizations of itaconic anhydride with electron-donating monomers, styrene and isobutyl vinyl ether, gave alternating copolymers which were then converted by esterification to the respective copolymers of dialkyl itaconates with such electron-donating monomers.     

Copolymerizations initiated by mechano-radicals on particle surfaces of poly(tetrafluoroethylene)

Mechanical fracture of solid poly(tetrafluoroethylene) (PTFE) produces main-chain scissions of the polymer, and free radicals, called mechano-radicals, are trapped on fresh surfaces generated by the fracture. These radical conversions were verified by ESR observation when several monomers—methylmethacrylate, vinylacetate, and ethylene—were brought into contact with these mechano-radical, and the copolymerizations of PTFE with these monomers were demonstrated. It was found that a new surface property, wettability of water, was added to the solid PTFE by the copolymerization with vinyl acetate, although the bulk nature of PTFE was not changed.     

ESR spectra of spin probe in PPO membrane

Poly(phenylene oxide) (PPO) polymer's membranes (dense) were prepared by blending spin probes (TEMPO, 5-, 12- and 16-doxylstearic aid) in the casting solution used for the preparation of membranes. It was noticed that the shape and size of the probe influence the ESR spectra of the NO radical in the poly(phenylene oxide)membrane. Unexpectedly, from the shape of the ESR signal it was noticed that of the NO radical of TEMPO in PPO membrane was more mobile than in water media. However, the motion of the NO radical of 16-doxylstearic acid was higher than NO of 5- and 12-doxylstearic acid when the radicals were in the PPO membrane. This could be due to the inductive effect from COOH group. The Hamiltonian parameters of the ESR signal indicated that all the probes were not randomly distributed in PPO membrane, but some probes were in orderly fashion.     

Radical polymerization of vinyl monomers in the presence of carbon black initiated by 2,2'‐azobisisobutyronitrile and benzoyl peroxide in ionic liquid

The radical polymerization behavior of vinyl monomers, such as styrene, methyl methacrylate (MMA), and vinyl acetate (VAc), in the presence of carbon black initiated by benzoyl peroxide (BPO) and 2,2'‐azobisisobutyronitrile (AIBN) in ionic liquid (IL) was compared with those in toluene. 1‐Butyl‐3‐methylimidazolium hexafluorophosphate was used as IL. The radical polymerization of vinyl monomers initiated by BPO and AIBN in the presence of carbon black was remarkably retarded in toluene. On the contrary, the retardation of the polymerization by carbon black was considerably reduced in IL. During the radical polymerization in the presence of carbon black, a part of polymer formed was grafted onto carbon black surface based on the termination reaction of the growing polymer radicals with carbon black surface. The percentage of grafting and molecular weight of polymer in IL were much higher than those in toluene. This may be due to the fact that lifetime of the growing polymer radical is prolonged because of high viscosity of IL. Therefore, the growing polymer radicals with higher molecular weight were trapped by carbon black surface, because of stabilization of polymer radicals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of highly conducting and spin-probed polypyrroles using coupled electrochemical-chemical synthesis in the presence of nitroxyl radicals

Summary A new method for the synthesis of conducting polypyrroles (PPy), based on chemical and combined electrochemical-chemical oxidation of pyrrole monomers in the presence of nitroxyl radical (TEMPOL-2,2,6,6-tetramethyl-4-hydroxy-1-oxy-piperidyl) as oxidation agent (in its oxidation state) and redox mediator respectively is described. The PPy films obtained are extremely porous and the electrical conductivity () of the resulting PPy samples ranges from 1 to 100 S cm^–1. PPy prepared in aqueous solutions has a lower conductivity 1 S cm^–1 as compared to the PPy prepared in acetonitrile solutions with conductivity of about 100 S cm^–1. The PPy films are quite compact and thick films (1 mm) can be pealed off from the electrode surface and pressed as a disc for further studies. Only after partial reduction of polypyrrole film the spin-probed PPy was obtained. The concentration of nitroxyl radicals incorporated in the polymer matrix can be changed using various degrees of polymer reduction. The anisotropic broadening of the observed ESR lines indicates a low mobility of incorporated nitroxyl radicals in the PPy matrix. The electronic interaction between the nitroxyl groups and the paramagnetic centers of the polymer chains, polarons, causes an ESR line broadening of polaron signal both on air (1.1 mT) and in vacuum (0.7 mT) as compared to unmodified PPy (0.2 mT on air, 0.05 mT in vacuum).     

THERMAL INDUCED HOMOLYTIC SCISSIONS OF LIGNIN INTERUNITARY BONDS IN THE HARDWOOD LIGNIN SOLUTION. AN ESR STUDY COMBINED WITH A SPIN TRAPPING METHOD

An electron spin resonance (ESR) method combined with a spin trapping reagent was successfully applied to trap and characterize unstable free radicals which were generated by heat-treatment of the dimethylsulfoxide (DMSO) solution of a hardwood, Japanese beech (Fagus crenata) lignin. It was found, consequently, that two unstable secondary carbon radicals, ～ CH? in the solution were created and the resulting radicals were trapped as the stable nitroxide spin adducts when the DMSO solution was heat-treated in the presence of a spin trapping reagent: 2,4,6-tri-tert-butylnitrosobenzene (BNB) at ca. 91°C. This means that so-called alkyl phenyl ether bonds, ～ CH-O- phenyl, known as important lignin interunitary bonds were homolytically scissoned by the heat-treatment of the lignin solution. Further the detailed analysis of the observed ESR spectrum revealed that two positions of alkyl phenyl ether bonds, i.e., β-O-4 and/or α-O-4 bonds as the interunitary linkages in the lignin are homolytically scissioned, although the phenoxy radical, Ph-O ? as the counter radical of the secondary carbon radicals was not trapped by the BNB spin trap. This suggests that fairly large steric hindrances operate between the syringyl with two methoxy moieties at the ortho positions and/or guaiacyl moieties with a methoxy moiety at the ortho position, and the BNB molecule bearing two bulky ortho tert-butyl groups in the phenyl ring.     

Preparation of monodispersed polymer-modified silica particles by radical polymerization using silica colloid and introduction of functional groups on the composite surface

Summary Radical polymerizations of vinyl monomers using a initiator of 2,2-azobis(2-amidinopropane) dihydrochloride on monodispersed silica colloid led to formation of spherical polymer/SiO₂ composites, retained particle size. Addition of hydroxypropyl cellulose to the reaction system resulted in yielding excellent dispersible composites into ethanol by short period ultrasonic irradiation. The polymerization of styrene in the presence of mercapto-amine or carboxylic acid derivatives could successfully introduce amino or carboxyl group on the Poly(styrene)/SiO₂ composite.     

Thermally induced homolytic scissions of interunitary bonds in a softwood lignin solution: A spin‐trapping study

Unstable chemical species, that is, radicals generated by the thermal treatment of a dimethyl sulfoxide (DMSO) solution of the lignin of a softwood, Yezo spruce (Picea jezoensis Carr.), were studied in detail with an electron spin resonance (ESR) method combined with a spin‐trapping technique. An unstable secondary carbon radical (～CH ·) in the solution was trapped as a stable nitroxide spin adduct [R? (N? O ·)? CH～ (R = tert‐butyl benzene)] when the DMSO solution was heat‐treated in the presence of a spin‐trapping reagent [2,4,6‐tri‐tert‐butylnitrosobenzene (BNB)] at about 40°C. This meant that alkyl phenyl ether bonds (～CH? O‐phenyl), known as interunitary lignin bonds, were homolytically scissioned by the thermal treatment in the lignin solution. A detailed analysis of the ESR spectrum revealed that three kinds of radicals—primary (～CH₂ ·), secondary (～CH ·), and tertiary (～C ·) carbon radicals—were trapped as stable spin adducts at about 60°C, although the phenoxy radical (Ph? O ·) was not trapped by the BNB spin trap as the counter radical of the secondary carbon radical. This suggested that a fairly large steric hindrance existed between the so‐called guaiacoxy radical with a methoxy group in the ortho position and the BNB molecule bearing two butyl groups as bulky moieties in the ortho positions. However, the phenoxy radicals in the lignin solution were stable up to about 60°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2136–2141, 2004     

Synthesis of macroporous polymers with radical scavenging properties by immobilization of polyphenolic compounds

Solid phase radical scavengers have been prepared by the immobilization of antioxidant (AOX) compounds on macroporous polymers. Poly(glycidylmethacrylate-co-trimethylolpropane trimethacrylate) [poly(GMA–TRIM)] and poly(N-acryloyl-tris(hydroxymethyl)aminomethane-co-glycidylmethacrylate-co-N,N′-methylenebisacrylamide) [poly(NAT–GMA–BIS)] were prepared by free radical polymerization using a mixture of dimethylsulfoxide (DMSO)-poly(ethyleneglycol) 6000 (PEG 6000) as a porogenic solvent. The polymers were aminated with ethylenediamine (EDA) and the linkage of the polyphenolic compounds (gallic and caffeic acids) was carried out by two different approaches: through N,N′-dicyclohexylcarbodiimide/4-dimethylaminepyridine (DCC/DMAP) system (one-step method) or through the previous formation of the acyl chloride of the polyphenolic compounds and subsequent amidation reaction (two-step method). The available phenolic groups on the macroporous polymers were determined using the Folin–Ciocalteu method; the radical scavenging properties of the materials prepared were evaluated using the radical species 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis-[3-ethylbenzothiazoline-6-sulfonic acid] radical cation (ABTS⁺). From the results, higher antiradical capacities were obtained with the polymers in which the immobilization of the antioxidant molecules was performed through the two-step method. The polymeric networks prepared in this work yielded up to 13.2 μmol AOX/g of dry polymer, which allowed a quantitative removal of the radicals tested in less than 30 min.     

ESR studies of free radicals in photo-initiated graft polymerization reactions with cotton cellulose

Electron spin resonance (ESR) spectra of free-radical intermediates formed during photo-initiated graft polymerization reactions of acrylamide, methacrylamide, and diacetone acrylamide onto purified cotton cellulose were recorded. Purified cellulose was saturated with aqueous solutions of the vinyl monomers (0.5M) and then photolyzed under nitrogen by near-ultraviolet light (3100–4100 Å, peak near 3500 Å) at ?196° and 40°C. Other samples of cellulose were saturated with aqueous solutions of the monomers, dried, and then photolyzed at 40°C. In the absence of cellulose, either poorly resolved or no free-radical spectra were generated on photolysis of the monomers. Photolysis of dried cellulose at 40°C and wet cellulose at ?196°C initiated formation of a cellulosic radical that generated a singlet spectrum. Photolysis of wet cellulose at 40°C generated no ESR detectable radical; however, photolysis of wet cellulose that contained monomer at 40°C generated poorly resolved spectra. The ESR spectra of the propagating copolymer radicals recorded were poly(acrylamide), three lines; poly(methacrylamide), five lines; and poly(diacetone acrylamide), two lines (doublet).     

Rate coefficient for radical desorption in emulsion polymerization

Investigators have proposed the rate coefficient for radical desorption from polymer particles to explain the kinetic deviation of the emulsion polymerization of water-soluble monomers such as vinyl acetate and vinyl chloride from the classical Smith and Ewart theory.⁶ In this article, the rate coefficient for radical desorption is theoretically derived by a different approach, and its applicability to vinyl acetate and vinyl chloride emulsion polymerization is examined in detail using experimental data available in the literature. The theory developed here predicts the average number of radicals per polymer particle in the emulsion polymerization of vinyl acetate and vinyl chloride.     

Overall rate of alternating copolymerization of vinyl acetate with maleic anhydride in methyl ethyl ketone

Summary The initial rate of radical copolymerization of vinyl acetate(D) and maleic anhydride(A) was measured dilatometrically in methyl ethyl ketone at 50°C. The rate was found to be maximum at the feed maleic anhydride mole fraction of 0.40,0.44 and 0.47 when the total monomer concentration was 0.75 M.1.50 M and 2.25 M, respectively. Participation of both free monomers and the complex was considered. Georgiev and Zubov's method gave =k_AD/k_DA=0.24, _A=k_AC/k_AC=35,_D=k_DC/k_DA =2.2 and k_AC/k_DC=3.9. The equilibrium constant of donor-acceptor complexation between vinyl acetate and maleic anhydride was determined to be 0.030 in acetonitrile at 27°C.     

Synthesis and characterization of poly(11-(4′-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether)

Summary Polymers based on 11-(4-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether have been synthesized by living cationic polymerization, photo-initiated cationic polymerization using onium salts and thermal initiated cationic polymerization using onium salts. The polymers have been characterized by size exclusion chromatography, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and polarized light microscopy. Living cationic polymerization resulted in a polymer of low molecular mass M_n3 600, with a uniformity index (D) of 1.2 displaying a focal conic texture indicative of smectic A (s_A) phase with preserved cyanogroup and trans-configuration. Photo-initiation using 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide and diphenyliodonium hexafluorophosphate resulted in an insoluble polymer exhibiting only vague liquid crystalline textures. Initiation with phenothiazine and phenacyltetramethylenesulfonium hexafluoroantimonate also yielded a partly insoluble polymer with a disturbed s_A phase. It is suggested that the monomer and polymer are sensitive towards radicals leading to cross-linking and branching. The thermal initiation on systems with -methylbenzyltetramethylenesulfonium hexafluorophosphate and p-methoxybenzyltetramethylenesulfonium hexafluorophosphate resulted in completely soluble mesomorphic polymers of M_n13 000, D=1.7 and M_n26 000, D=2.8 respectively, in both cases with a preserved cyanogroup and a transconfiguration. Polarized light microscopy revealed a distinct focal conic structure indicative of s_A in both cases.     

Radikalreaktionen an N-Heterocyclen. XI. ESR-spektroskopischer Nachweis von Radikalen der 3-Methyl-pyrazolin-5-one

Free Radical Reactions of N-Heterocyclic Compounds. XI. ESR-Study of Radicals of 3-Methyl-pyrazolin-5-ones The oxidation of 1,4-substituted 3-methylpyrazolin-5-ones ( 1a – p ) led to pyrazolinonyl radicals ( 2a – p ), which were detected directly or after trapping with nitrosobenzene as phenyl nitroxides. In a few cases, the products of oxidation of pyrazolin-5-ones ( 1 ) with electron-withdrawing groups in 4-position by peroxy radicals were endo cyclic nitroxides ( 8 ), which were also detected by ESR spectroscopy.     

The effect of active azodyes on the polycaproamide photo-oxidation kinetics

Investigations were carried out on polycaproamide films(PCA) at room temperature in air. Samples were dyed with oxyethylsulfonic and monochlortriasinic active dyes. Irradiation was carried out with a low-pressure Hg lamp (λ = 254 nm, intensity equals 1.5 × 10¹⁵ sm^?2 sec^?1). During irradiation, ESR spectra of five poorly resolved lines of superfine structure were observed for all samples. Analysis of ESR spectra shows that quintet belongs to radicals $ \sim {\rm CONH\dot CHCH}_{\rm 2} \sim $. The initial accumulation rate of radicals was measured on linear parts of radical accumulation curves. Similarly, accumulation of PCA carboxyl groups kinetics was measured. The initial accumulation rates of radicals and carboxyl groups are linear functions of absorbed radiation on polymer and dye. There is a tendency of increasing carboxyl group yields with radical yields for different dyes. One can assume that it follows from this correlation that radicals are precursors of carboxyl groups. Luminescence spectra measured for PCA with salt and covalent bonded dyes are located near 425 nm. The data allow the conjecture that PCA luminescence is connected with centers bonded with PCA macromolecules.     

Graft polymers with macromonomers. I. Synthesis from methacrylate-terminated polystyrene

Pure graft polymers having uniform molecular weight polystyrene side chains were prepared by free radical copolymerization of methacrylate-terminated polystyrene macromonomers (MA-CROMER) with ethyl acrylate, butyl acrylate, or other suitable monomers. The MACROMER monomer was synthesized by living anionic polymerization under conditions that led to very narrow molecular weight distributions. Very effective end capping produced a material that was highly monofunctional. The graft copolymers were prepared by several techniques such as free radical solution polymerization, by aqueous suspension polymerization which produced beads, or by emulsion reactions which yielded stable latices. Polymerizations were reproducible. High conversion of the MACROMER monomer into pure graft polymers was achieved, and the product was contaminated with only a little homopolymer. The milled and molded phase-separated graft polymers had optical clarity and physical properties characteristic of polystyrene-reinforced triblock polymers. Compositions of 20-30% polystyrene were thermoplastic elastomers with good recovery. When polystyrene contents were increased, the graft products were strong, flexible thermoplastics with well defined yield strengths and increased permanent set. Copolymers of polystyrene macromers with acrylonitrile or vinyl chloride produced transparent polystyrene homopolymer-free graft polymer products having improved processing over polyacrylonitrile or poly(vinyl chloride) homopolymers.     

An esr study of radical intermediates formed by γ - radiolysis of tripalmitin and dipalmitoyl phosphatidylethanolamine

Radicals resulting from the 7-radiolysis at 77 K of neat tripalmitin and neat dipalmitoyl phosphatidylethanolamine were investigated by electron spin resonance spectroscopy (ESR). Analyses of the spectra of these complex lipids were aided by ESR studies of their components phosphorylethanolamine, palmitic acid and hexa-decane. Concentrations of various radicals were followed as a func-tion of temperature after γ-irradiation at 77 K. Both tripalmitin and dipalmitoyl phosphatidylethanolamine show anion radicals formed by electron addition to the ester groups and aliphatic side-chain radicals (-CH₂-CH-CH₂-) which are thought to be the result of deprotonation of the original positive hole. Computer analyses of the spectra as the temperature increases show loss of the anion radicals with an increase in a new radical produced by the abstrac-tion of a hydrogen atom from the α carbon on an acyl side chain. In the case of dipalmitoyl phosphatidylethanolamine, a radical of the phosphorylethanolamine portion of the molecule is detected as an intermediate. Mechanisms for the formation and decay of the free radical intermediates are discussed.     

Effect of electron-withdrawing type substituents in the polyaniline ring on the electrical conductivity

Summary Poly(ethyl 3-aminophenyl formate), poly(ethyl 3-aminophenyl acetate) and poly(ethyl 3-aminophenyl propionate) were synthesized in 1 M HCl media from respective monomers using ammonium persulphate as oxidizing. The polymers were characterized by FT-IR, UV-vis and ¹H-NMR spectroscopy. The effect of electron-withdrawing on the electrical conductivity of polyaniline, was studied. The electron-withdrawing group (ester) bond to the aniline ring affects the formation of charge carriers and electrical conductivity of polymers, therefore, at various bond lengths of the aniline ring, the electron-withdrawing effect decreases and a polymer with electrical conductivity from the semi-conduction order is obtained.     

Electron spin resonance study of γ-irradiated nylon 6

The free radicals trapped in oriented nylon 6 filaments after γ-irradiation under vacuum at room temperature were studied by ESR spectroscopy. The ESR spectrum measured after irradiation gradually changed to a broad singlet spectrum with decrease in the intensity. The ESR spectrum consisted of radicals with different orientation effects with respect to the outer magnetic field, and saturation effects in reference to microwave power. The simulation of the ESR spectrum from a Gaussian function gave a better fit to the observed spectrum than the calculation from a Lorentzian function. From the resolution of the spectrum from a Gaussian function, the observed spectrum is generated from three kinds of radicals: The relative radical concentration for the first, second, and third radical is about 75%, 6%, and 19% of the total radical concentration, respectively. With regard to the stability of the radicals, the third radical shows a comparatively long lifetime. The first and second radicals show almost identical lifetime, and their concentrations reduce to about 40% of the initial value during the 2 days at room temperature.     

Surface grafting of polymers onto ultrafine silica: Cationic polymerization initiated by oxoaminium perchlorate groups introduced onto ultrafine silica surface

Summary The cationic polymerization initiated by oxoaminium perchlorate groups introduced onto ultrafine silica surface was investigated. The oxoaminium perchlorate groups were successfully introduced by treatment of nitroxyl radicals on silica surface with perchloric acid. The introduction of the nitroxyl radicals was achieved by reaction of 4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy radical with acid anhydride groups on the surface. The cationic polymerization of isobutyl vinyl ether, N-vinylcarbazole, 2,3-dihydrofuran, and -butyrolactone was initiated by oxoaminium perchlorate groups introduced onto the surface and the corresponding polymers were grafted onto the surface through the propagation of grafted polymer chain from the surface oxoaminium perchlorate groups.