Starch and amylose degradation by 60Co γ-irradiation

The effects of γ-irradiation (0.02–4.0 Mrad absorbed dose and 1.2 Mrad/hr dose rate) on depolymerization and selected physical properties of corn starch and amylose (both dry solid and solution forms) were investigated under conditions used to make graft polymers. Radiation introduces an alkali-sensitive structure, most likely β-alkoxycarbonyl, having a G value of 2.8. A dimethyl sulfoxide (DMSO)-acetic acid-water solvent for intrinsic viscosity was developed that degraded irradiated amylose less than did aqueous 90% DMSO. The G (scission) value of 1.3 for solid amylose irradiated at 0°C under nitrogen is lower than most literature values for either amylose or other polysaccharides. The protection of amylose against irradiation degradation in water by additions of DMSO is noteworthy. The G (scission) for amylose irradiated in 99.8% DMSO is 2.3; whereas, in water it is 30.     

Effects of cobalt-60 γ-ray irradiation on fresh-keeping and storage of kiwifruits

The boxes contained kiwifruits were irradiated with cobalt-60 γ-rays at different dosages (0.6 , 1.8 and 3.6 KGy) and stored in a room ventilated at night, the natural ambient air being used as cool source.The results showed that the treatment which fruits irradiated with 0.6 KGy was the best after 85 days. It gave the normal-fruit rate of 95.10%, fruit flesh hardness of 4.10 Kg · cm^-2, fresh and plump fruits, good quality and less Vc loss.     

Co60 γ-radiation-induced copolymerization of ethylene and carbon monoxide

The γ-radiation-induced free-radical copolymerization of ethylene and CO has been investigated over a wide range of pressure, initial gas composition, radiation intensity, and temperature. At 20°C., concentrations of CO up to 1% retard the polymerization of ethylene. Above this concentration the rate reaches a maximum between 27.5 and 39.2% CO and then decreases. The copolymer composition increases only from 40 to 50% CO when the gas mixture is varied from 5 to 90% CO. A relatively constant reactivity ratio is obtained at 20°C., indicating that CO adds 23.6 times as fast as an ethylene monomer to an ethylene free-radical chain end. For a 50% CO gas mixture, the above value of 23.6 and the copolymerization rate decrease with increasing temperature to 200°C. The kinetic data indicate a temperature-dependent depropagation reaction. Infrared examination of copolymers indicates a polyketone structure containing ? CH₂? CH₂? and ? CO? units. The crystalline melting point increases rapidly from 111 to 242°C., as the CO concentration in the copolymer increases from 27 to 50%. Molecular weight of copolymer formed at 20°C. increased with increasing CO, indicating M?_n values >20,000. Increasing reaction temperature results in decreasing molecular weight. Onset of decomposition for a 50% CO copolymer was measured at ≈250°C.     

ATRP of MMA under 60Co γ‐irradiation at room temperature

In this work, atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out at room temperature (25 °C) under ⁶⁰Co γ‐irradiation environment. The polymerization proceeded smoothly with high conversion (>90%) within 7 h. The polymerizations kept the features of controlled radical polymerization: first‐order kinetics, well‐predetermined number‐average molecular weights (M_n,GPC), and narrow molecular weight distributions (M_w/M_n < 1.25). ¹H NMR spectroscope and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry confirmed that poly(methyl methacrylate) (PMMA) chain was end‐capped by the initiator moieties. The Cu(II) concentration could reduce to 20 ppm level while keeping good control over molecular weights. This is the first successful example for the ATRP of MMA under ⁶⁰Co γ‐irradiation at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A study on feasibility of insect—control with γ-ray

Insect-control with Co-γ-ray is a method for conserving archives, books, cotton textiles, historical relics, wood structured houses and furniture, which are called irradiated objects later on. The temporary and residual effects of γ-ray on irradiated objects and the biological effects on insects are presented in this report.

Our study shows that there is no obvious harmful effect on irradiated objects when the ray is below 870 Gy, while there is obvious deterioration on the objects when the ray is above 870 Gy. On the other hand, the ray below 870 Gy is strong enough for the insects. In fact, at the dose of 43.5–130.5 Gy, the irradiated insects could be damaged on reproductive function, even sterilized, or killed.     

Temperature-induced transformations of peroxide radicals formed in polytetrafluoroethylene with γ-ray irradiation

At 200°C, temperature-induced transformations of peroxide radicals from ? CF₂CF(OO·)CF₂? (radical I) to ? CF₂CFCF₂? (radical 1) and ? CF₂CF₂OO· (radical II) to ? CF₂CF₂ (radical 2) in vacuo, and from I to II in oxygen atmosphere were observed. In these thermal transformations, the evolution of CO₂ with a small amount of CO and CF₂O was observed. Further, measurements of the heat of crystallization of the treated polytetrafluoroethylene suggest that a reduction of polymer molecular weight occurs during the transformations from I to 1 and I to II.     

Isomerization polymerization of 2-vinyl-1,3-dioxolane by α,α′-azobisisobutyronitrile or by γ-ray irradiation

2-Vinyl-1,3-dioxolane was polymerized by use of α,α′-azobisisobutyronitrile (AIBN) or by γ-ray irradiation. The polymer obtained was white amorphous powder which melted at ca. 70°C. and was soluble in chloroform, acetone, and p-dioxane. The infrared spectrum of the polymer indicated peaks at 1735 cm.^?1 characteristic of the carbonyl group, and at 1200–1000 cm.^?1 characteristic of the acetal group, while no absorption at 990 and 3100 cm.^?1 due to the vinyl group was observed. The spectra of the polymers obtained by AIBN and by γ-ray irradiation were essentially identical. The saponified product of the polymer was white powder and its reduced viscosity was a little larger than that of the original polymer. These results indicate that the polymer has no ester unit in the main chain. The results of gas chromatographic analysis of the saponified product of the polymer, indicate the presence of a small amount of ethyl alcohol. The results of the saponification showed that the ester content in the polymer varied from 7 to 25% depending upon the polymerization temperature. These results indicate that 2-vinyl-1,3-dioxolane polymerized by AIBN or by γ-irradiation with two modes of vinyl and hydrogen migration, yielding a copolymer having the unit structures      

The preparation and γ-ray sensitivity of comb block copolymers

A series of comb block copolymers have been prepared and subjected to ⁶⁰Coγ irradiation. The copolymers contained a polyalkenesulphone backbone, and either polystyrene or polymethylphenylsiloxane as the sidebranches. The alkenes in the polysulphone were one of cycloheptene, 2-hexene, or 2-methylpentene-1 giving a series of backbones of differing low ceiling temperatures. The combs were prepared by creating a macromer of the desired sidearm, and then copolymerizing into the main chain. On γ-irradiation, backbone polysuphones depolymerized leaving behind the comparatively short and radiation resistant sidechains.     

Encapsulation of Hb into unsaturated lipid vesicles and γ-ray polymerization

A carbonyl hemoglobin (HbCO) solution was stirred with a mixed powder of polymerizable 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine (DODPC), cholesterol and stearic acid (7/7/2 by mol). The mixture was extruded through polycarbonate membrane filters (final pore size = 0.2 μm Ø). The average diameter of the resulting vesicles was 203 ± 39 nm. The [Hb]/[Lipid] ratio (the weight ratio of Hb in vesicle to lipid) increased with the Hb concentration, and decreased with the NaCl concentration. A maximum [Hb]/[lipid] ratio was observed at pH 6.9, which was the same as the isoelectric point of Hb. The vesicles were stabilized by γ-irradiation (⁶⁰Co) because the bilayer lipids bound each other to yield polyphospholipids. Denaturation of Hb by γ-irradiation was not detected. These polyphospholipid vesicles encapsulating Hb were stable even against the freeze–thaw cycles and the freeze-drying procedure.     

Effect of γ-ray and photoirradiation on very low density polyethylene

The fourth type of polyethylene—very low density polyethylene (VLDPE)—has been developed very recently. VLDPE is a copolymer of ethylene and 1-butene. The radiation and photo degradation of VLDPE was studied using gel, FT-IR, and UV spectral measurements. Mechanical tests were also done; the rate of gel and carbonyl formation was high. End methyl ? CH₃ group was found to increase in the case of radiation degradation. The initial modulus was very low indicating the rubbery nature in the copolymer. VLDPE was found to be highly resistant to radiation-induced degradation than linear low density polyethylene. VLDPE is highly susceptible to thermal effects.     

γ-ray and ultraviolet graft copolymerization of maleimide by vapor-phase method

Graft copolymerization of maleimide onto ethyl cellulose and polyethylene films by using its sublimation vapor was carried out under γ- or ultraviolet irradiation. When polyethylene film was used as a backbone polymer the grafting reaction proceeded without a perceptible sorption of monomer, while a considerable amount of monomer was captured into ethyl cellulose film and grafting of the sorbed monomer was observed. The monomer seemed to be monomolecularly dispersed in this film. The presence of air retarded the reaction. The grafted films were characterized by strong infrared absorption bands due to polymaleimide branching. The fractions assigned to the graft copolymer were isolated from the grafted films by selective elution. The grafted branches were supposed to be very short, judging from the polymaleimide contents of those fractions.     

Alternative copolymerization of aziridines and carbon monoxide by γ-ray irradiation

The copolymerization of carbon monoxide and aziridines such as ethylenimine and propylenimine was carried out by γ-ray irradiation. Aziridines and carbon monoxide were allowed to copolymerize under γ-ray irradiation from a Co⁶⁰ source and gave a crystalline solid copolymer. The yield of the copolymer increased with reaction temperature. The composition of copolymers obtained did not depend on the feed ratio of monomers and was found to be almost equimolar. The copolymer of ethylenimine and carbon monoxide melted at about 322–335°C. with decomposition and has an infrared spectrum identical with that of poly-β-alanine obtained by the hydrogen-migration polymerization of acrylamide. The hydrolyzed product of the ethylenimine–carbon monoxide copolymer was confirmed to be β-alanine by paper chromatography. These results lead to the conclusion that the copolymerization of aziridines and carbon monoxide took place alternatively by γ-ray irradiation, and produced crystalline poly-β-alanines.     

Solid-state polymerization studies. I. 2-vinylnaphthalene post-polymerization initiated by 60Co γ-irradiation

⁶⁰Co γ-irradiated 2-vinylnaphthalene was obsreved to post-polymerize in the solid phase. Plots of conversion versus time indicated a 14% limiting conversion of monomer to polymer. The post-polymerization was found to be first-order in monomer with an Arrhenius activation energy of 19.0 kcal./mole.     

Immune response against antigens irradiated with 60Co gamma-rays

Summary In the present work, we investigated the immunological behavior of bothropstoxin-1, a K49 phospholipase from Bothrops jararacussu, and of ovalbumin before and after irradiation with ⁶⁰Co g-rays. Isogenic mice were immunized with either native or irradiated proteins. The circulating antibodies were isotyped and titrated by ELISA. Results indicate that irradiated proteins were immunogenic and the antibodies elicited by them were able to recognize the native proteins in ELISA. Data also indicate that the irradiated protein induced higher titers of IgG2a and IgG2b, suggesting that Th1 cells were predominantly involved in the immune response. Structural modifications of the proteins were investigated by SDS-PAGE, mass spectrometry and size exclusion chromatography. According to our data, irradiation promoted structural modifications on both proteins, characterized by higher molecular weight forms (aggregates and oligomers). When analyzed by mass spectrometry, the irradiated bothropstoxin appeared in several oxidized forms. These results indicate that irradiation of toxic proteins can promote significant modifications in their structures, but still retain many of the original antigenic and immunological properties of native form.     

Kinetics of γ-ray polymerization of formaldehyde in the presence of carbon dioxide

A kinetic study of the γ-ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to ?17°C. Two modes of the polymerization, spontaneous and γ-ray polymerization, occur in this system. The γ-ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ-ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ-ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ-radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ-ray polymerization were also investigated.