Poly Groups Research Articles

ChemInform Abstract: EPR STUDIES OF THE MOLECULAR MOTION OF NITROXIDE RADICALS IN POLY(VINYL ALCOHOL) GELS

Chemischer InformationsdienstVolume 11, Issue 44 Physical Organic Chemistry ChemInform Abstract: EPR STUDIES OF THE MOLECULAR MOTION OF NITROXIDE RADICALS IN POLY(VINYL ALCOHOL) GELS T. WATANABE, T. WATANABESearch for more papers by this authorT. YAHAGI, T. YAHAGISearch for more papers by this authorS. FUJIWARA, S. FUJIWARASearch for more papers by this author T. WATANABE, T. WATANABESearch for more papers by this authorT. YAHAGI, T. YAHAGISearch for more papers by this authorS. FUJIWARA, S. FUJIWARASearch for more papers by this author First published: November 4, 1980 https://doi.org/10.1002/chin.198044078AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue44November 4, 1980 RelatedInformation

E.s.r. study of free radicals in poly(vinyl carbazole)

Poly(N-vinylcarbazole) was γ-irradiated at 77 K. The analysis of e.s.r. spectra showed that cation radicals centred at N were produced in the system. Hyperfine splitting constants are: a N =0.57 mT and a H β =0.68 mT. The dependence of the rate constant of free radical decay on pressure (1–800 MPa) was studied at various temperatures (90–170°C). Activation volumes were determined for two characteristic pressure and temperature ranges. The results of e.s.r. measurements are compared with those obtained from dynamic-mechanical measurements.

EPR studies of the molecular motion of nitroxide radicals in poly(vinyl alcohol) gels

EPR studies of the molecular motion of nitroxide radicals in poly(vinyl alcohol) gels

Thermal‐induced conversion of maleic and fumaric acid anion radicals in poly(methyl methacrylate)

AbstractThermal‐induced conversion of maleic and fumaric acid anion radicals produced by γ irradiation at 77 K in poly(methyl methacrylate) (PMMA) was studied by electron spin resonance (ESR) and optical absorption spectroscopic measurements. The ESR spectra of these acid anion radicals change into two‐line spectra with a line separation of ca. 10 G by thermal annealing. This spectrum is assigned to a protonated radical of each acid anion radical. Anion radicals of the solutes are relatively stable below the γ transition point of PMMA and the conversion reaction takes place near this point. This means that the molecular motion of matrix molecule affects the radical conversion reaction.

Thermal degradation mechanism of poly- p-phenylene sulphides

A study was made of main mechanisms governing thermal and thermal-oxidizing breakdown of linear poly- p-phenylene sulphide. The existence of two temperature regions of thermal conversion of poly- p-phenylenesulphide was established. EPR was used to study main regularities of the formation of stable radicals during thermal conversion of poly- p-phenylene sulphide. Absolute concentrations of stable radicals in poly- p-phenylene sulphide sample heat treated in the temperature region of 350–600° were determined. It was shown that the reaction medium has no marked effect on thermal properties of poly- p-phenylene sulphide and decomposition of the weakest PhS bonds is the primary stage in thermal breakdown of polymers.

Etude par resonance magnetique nucleaire du carbone-13 des polymethacrylates de naphtyle-1 et de naphtyle-2 obtenus par voie radicalaire

Radical poly(naphthyl-1 methacrylate) and poly(naphthyl-2 methacrylate) have been examined by [ 13C]NMR. Quantitative determination of the tacticity of pentads is only possible with poly(naphthyl-2 methacrylate). The propagation of the stereosequences is found to be nearly bernouillian.

Additional broadening of electron‐spin‐resonance spectra of nitroxyl radicals in poly(ethylene oxide)

Additional broadening of electron‐spin‐resonance spectra of nitroxyl radicals in poly(ethylene oxide)

ESR studies of the radiation‐induced multiple graft polymerization

AbstractThe radiation‐induced multiple‐graft polymerization was studied by an ESR method. When methyl methacrylate vapor was introduced onto preirradiated polyethylene already grafted with styrene, the second step of grafting of methyl methacrylate occurred mainly in the polyethylene portion. The kinetic treatment proved that the termination rate constant kt of methyl methacrylate decreased with the amount of styrene grafted in advance. On the other hand, when styrene vapor was introduced onto polyethylene grafted with methyl methacrylate, only radicals of poly(methyl methacrylate) decreased. In this case, the second step of grafting of styrene occurred in the poly‐(methyl methacrylate) portion which covered the whole surface of the polyethylene powder. When monomer vapors were alternately introduced onto preirradiated polyethylene powder, the second step of grafting occurred at the growing chain end of the first monomer.

Isobaric temperature dependence of radical generation in poly(methyl methacrylate)

AbstractIn this study the effect of temperature on the generation of free radicals accompanying the decomposition of benzoyl peroxide in poly(methyl methacrylate) was studied. The concentration of the chain‐end radicals was determined by the ESR method. The known nine‐line spectrum of the chain‐end radicals of poly(methyl methacrylate) was observed. This spectrum was affected by the contribution of chain radicals at higher temperatures. The dependence of the chain‐end radical concentration on the annealing temperature of polymer found for different pressures gives information on the conditions under which free radicals arise and decay in the temperature range between 90 and 170°C at pressures ranging from 2000 to 12000 atm.

On the formation of tert‐butyl radicals after irradiation of polymers containing tert‐butoxycarbonylthioethylene units

AbstractThe formation and the behaviour of radiation induced free radicals in poly[1‐(tert‐butoxy carbonylthio)ethylene] (2) and in a statistical copolymer 4 from O‐tert‐butyl S‐vinyl thiocarbonate (1) with N‐vinylpyrrolidone (1:1) was studied, using ESR spectroscopy. After γ‐irradiation at 77 K, tert‐butyl radicals and other species were detected in the polymers. The yield for the homopolymer was evaluated to be Gtert‐butyl = 0.18. Investigations on the behaviour of radicals with an annealing procedure revealed, that at first the tert‐butyl radicals disappear with increasing temperature and that a further warming up leads to a concentration rise of this radical species. A radical cation localized at the carboxy group is assumed as precursor of this reaction. Further reactions are discussed.

Radical-induced ionic polymerization in the presence of maleic anhydride. III. Polymerization of isobutyl vinyl ether initiated by trapped radicals in poly(maleic anhydride)

In a previous paper1 it was mentioned that trapped radicals in poly(maleic anhydride) (Poly-MAH) have the ability to initiate cationic polymerization. In this paper, the cationic polymerization of isobutyl vinyl ether (IBVE) is described using Poly-MAH as the initiator. These radicals show different behavior during polymerization depending upon their structure. In particular, large conjugated radicals initiate ionic polymerizations.

The Synthesis and Polymerization of Phenylvinyloxyboranes

Phenyldivinyloxyborane, PhB(OCH=CH2)2(DVOB), and chlorophenyl-vinyloxyborane, PhB(OCH=CH2)Cl(VOBCl), were synthesized by the reaction of phenyldichloroborane and mercuridiacetaldehyde. Diphenylvinyloxyborane (VOB) and di-n-butylvinyloxyborane were not isolated from the reaction mixture because of their rapid spontaneous polymerization.DVOB was polymerized by radical and cationic initiators. Poly(DVOB) polymerized with radical initiators was found to have a perfectly cyclized structure with exclusively six-membered rings. On the other hand, cationically polymerized polymers were highly crosslinked, indicating incomplete cyclization. The radical poly (DVOB) was converted into poly(vinyl alcohol) by hydrolysis, the tacticity of which was found to be slightly isotactic.VOBCl was also polymerized by radical initiators, yielding polymers which had structures similar to the radical poly(DVOB), indicating the occurrence of a cyclization and elimination reaction during the polymerization. VOBCl was not polymerized by cationic initiators.VOB was polymerized spontaneously and was ascertained to have been polymerized by a radical mechanism.

Determination of glass transition temperature of poly(ethylene glycol) by spin probe technique

The rotational relaxation data for free nitroxyl radicals in poly(ethylene glycol) samples of mol. wt 3000-22,000 gave for the glass-transition temperature ( T p ) a value of −60°, independent of molecular weight. The rotational activation energy was ∼ 2 kJ/mole below T g and ∼ 10 kJ/mole above T g . This indicated that the mechanism of motion below T g differs from the above T g . Evidently the rotating units of polymer are much smaller below T g than above it. The rotational relaxation time (T) was found to be dependent on the molar volume of PEG (V) and to follow the empirical equations t = A exp (−kV 1) and t = B exp (−k V 1) where V a and V 1 are the molar volumes (cm 3/mol) when T < T g and T > T g respectively, and k ∼ 1. Therefore the defects in which radicals are located are perhaps the dominant factor determining the dynamic state of probe radicals in polymers at low temperatures.

Thermodynamics of the stereosequence propagations in the radical polymerization of vinyl chloride studied by 13C‐NMR and IR

AbstractThe variation of the tacticties of radical poly(vinyl chloride)s as a function of the polymerization temperatures has been examined by 13C‐NMR (in terms of triads and tetrads) and IR (in terms of dyads). It has been observed that BERNOUILLIan statistics could be verified at 0°C for radical polymerization in bulk. The calculated values of differential enthalpies and entropies of activation revealed that, relatively, radical poly(methyl methacrylate)s propagate more easily in syndiotactic placement than radical poly(vinyl chloride)s.

Copolymerization with Depropagation. II. Rate of Copolymerization of Styrene α - Methylstyrene

Abstract Styrene and α-methylstyrene have been copolymerized at 60°C. At this temperature depropagation of the latter monomer must be considered. The rate of copolymerization and the chain length of the polymer formed are quantitatively interpreted by an extension of the theory previously used to describe the copolymer composition. It is postulated that rapid termination of copolymerization occurs because of the presence in the systems of low molecular weight free radicals of poly(α-methylstyrene) of chain length 3 cr less.

Polymerization of vinyl chloride in the presence of chain transfer agents

AbstractTo elucidate the chemical factors influencing the structure of radical poly(vinyl chloride) the effect of chain transfer agents was studied. With decreasing degree of polymerization P the association capability of the polymer slowly decreases. From the region of about P = 250 down the aggregation abruptly increases independently of the chain transfer agent used. The influence of copolymerization with a small amount of vinyl acetate under the conditions given was followed. The stereoregularity of the products formed and the content of foreign groups were determined. The results were correlated with kinetic data. The conditions of formation of poly(vinyl chloride) with a regular structure and a strong ability to aggregate are discussed.

Radiolysis of the isomeric poly(butyl methacrylates)

AbstractA study has been made of the effect of gamma irradiation on the production of free radicals in poly(butyl methacrylates). A mechanism of radiation attack on the polymers is proposed. Free‐radical measurements and the determination of the products of irradiation have been used in establishing this mechanism. The effects of configuration of the ester chain on radiation susceptibility are discussed.