Effects of sensitizer length on radiation crosslinked shape–memory polymers

Shape–memory polymers (SMPs) are smart materials that can be designed to retain a metastable state and upon activation, recover a preprogrammed shape. In this study, poly(methyl acrylate) (PMA) is blended with poly(ethylene glycol) diacrylate (PEGDA) of various molecular weights in various concentrations and subsequently exposed to ionizing radiation. PEGDA sensitizes the radiation crosslinking of PMA, lowering the minimum absorbed dose for gelation and increasing the rubbery modulus, after crosslinking. Minimum dose for gelation, as determined by the Charlesby–Pinner equation, decreases from 25.57 kGy for unblended PMA to 2.06 kGy for PMA blended with 10.00 mole% PEGDA. Moreover, increase in the blend concentration of PEGDA increases the crosslinking density of the resulting networks. Sensitizer length, namely M_n of PEGDA, also affects crosslinking and final mechanical properties. Increase in the length of the PEGDA molecule at a constant molar ratio increases the efficacy of the molecule as a radiation sensitizer as determined by the increase in gel fraction and rubbery modulus across doses. However, at a constant weight ratio of PEGDA to PMA, shorter PEGDA chains sensitize more crosslinking because they have more reactive ends per weight fraction. Sensitized samples of PMA with PEGDA were tested for shape–memory properties and showed shape fixity of greater than 99%. Samples had a glass transition temperature near 28 °C and recovered between 97% and 99% of the induced strain when strained to 50%.     

Controlling the gelation temperature of biomimetic polyisocyanides

The gelation temperature and mechanical properties of aqueous ethylene glycol-decorated polyisocyanide solutions strongly depends on the length of the glycol tail. Copolymerisation of monomers with different tail lengths allows for precise engineering of the gel properties.     

The effect of sodium dodecyl sulfate solutions as gelation media on the formation of PES membranes

Sodium dodecyl sulfate (SDS) aqueous solutions were used as gelation media in the preparation of polyethersulfone (PES) membranes. The casting solution composition was the same for all the tested membranes. The temperatures of gelation media were 4 and 20°C. The concentration of SDS was changed from 0 to 3.0 g/l at 4°C and 0 to 1.6 g/l at 20°C.The surface tension of the gelation media was measured by drop weight method and the electrical conductivities were also determined. The membranes were characterized by transport parameters obtained from separation experiments and roughness parameters, obtained by the atomic force microscopic (AFM) technique.The molecular weight cut-off (MWCO) values of the studied membranes were found to be between 9 000 and 88 000 Da for membranes gelled at 4°C, and between 28 000 and 85 000 Da for membranes gelled at 20°C. The pore sizes were found to be between 3.04 and 10.73 nm for the membranes gelled at 4°C and between 4.48 and 10.74 nm for membranes gelled at 20°C, respectively. In general, both MWCO and pore size decreased with an increase of SDS concentration in gelation media when the concentration was below critical micelle concentration (CMC) and increased with an increase with SDS concentration when the concentration was above CMC. Images of membrane surfaces, taken by AFM, showed that the size of nodules and depressions decreased with a decrease in pore size. The roughness of membranes increased with an increase in pore size and MWCO.     

Studies of network organization and dynamics of e-beam crosslinked PVPs: From macro to nano

In this work the influence of poly(N-vinyl pyrrolidone) (PVP) concentration in water on the organization and dynamics of the corresponding macro-/nanogel networks has been systematically investigated. Irradiation has been performed at the same irradiation dose (within the sterilization dose range) and dose rate. In the selected irradiation conditions, the transition between macroscopic gelation and micro-/nanogels formation is observed just below the critical overlap concentration (～1 wt%), whereas the net prevalence of intra-molecular over inter-molecular crosslinking occurs at a lower polymer concentration (below 0.25 wt%). Dynamic–mechanical spectroscopy has been applied as a classical methodology to estimate the network mesh size for macrogels in their swollen state, while ¹³C NMR spin–lattice relaxation spectroscopy has been applied on both the macrogel and nanogel freeze dried residues to withdraw interesting information of the network spatial organization in the passage of scale from macro to nano.     

Studies on enhancing the keeping quality of peach (Prunus persica Bausch) Cv. Elberta by gamma-irradiation

The effect of gamma-irradiation on keeping quality of peach fruit was studied. The fruit, after harvesting at proper maturity stage, was irradiated in the dose range of 1.0–2.0 kGy, stored under ambient (temp. 25±2 °C, RH 70%) and refrigerated (temp. 3±1 °C, RH 80%) conditions and evaluated periodically for firmness, total soluble solids (TSS), anthocyanins, water-soluble pectic fractions, loss in weight and decay percentage. The anthocyanin evaluation of the fruits revealed that irradiation enhanced the colour development under both the storage conditions. The gamma-irradiation dose range of 1.2–1.4 kGy proved effective in maintaining higher TSS concentration, reducing weight loss and significantly (p⩽0.05) delaying the decaying of the fruit by 6 days under ambient conditions and by 20 days under refrigerated storage conditions.     

Interactions between ethyl(hydroxyethyl) cellulose and lysine-based surfactants in aqueous media

In this work, the interaction between ethyl(hydroxyethyl) cellulose (EHEC) and three dimeric lysine-based surfactants of distinct chain length (C₆, C₈ and C₁₀) have been assessed and the system was evaluated in terms of its temperature-dependent gelling capacity. The viscosity profile depends on the specific surfactant, its concentration and temperature. The observed profiles reflected polymer–polymer associations at elevated temperatures and polymer-surfactant interactions, implying the formation of micellar-type associations. The systems induce gelation at higher temperatures. Longer chain-length surfactants induce gelation at lower concentrations due to their stronger tendency to self-assemble. The thermo-responsive gels showed gel strength generally lower than 20 Pa.sⁿ and a fractal dimension of 2.3–2.4, respectively, indicating the formation of soft gels comprising a tight and homogeneous network. The weakest gel was produced in the presence of the C₆ surfactant. 2D Small-Angle Light Scattering patterns showed a pronounced effect of temperature in terms of the evolution of large hydrophobic clusters, an event precluded when high concentrations of the longer chain surfactants were used.     

A study on size effect of carboxymethyl starch nanogel crosslinked by electron beam radiation

The formation of carboxymethyl starch (CMS) nanogel with 50 nm less particle size was carried out through a radiation crosslinked process on the electron beam (EB) linear accelerator. Changes of intrinsic viscosities and weight averaged molecular weight in the CMS concentration, which ranged from 3 to 10 mg ml^?1 in absorbed doses were investigated. There were some new peaks in the ¹H NMR spectra of CMS nanogel compared with those of CMS polymer. These results were anticipated that the predominant intramolecular crosslinking of dilute CMS aqueous solution occurred while being exposed to a short intense pulse of ionizing radiation. Hydrodynamic radius (often called particle size, R_h) and distribution of particle size were measured by a dynamic light scattering technique. The radiation yield of intermolecular crosslinking of CMS solution was calculated from the expression of G_x (Charlesby, 1960, Jung-Chul, 2010). The influence of the “size effect” was demonstrated by testing culture of Lactobacillus bacteria on MRS agar culture medium containing CMS nanogel and polymer. Results showed that the number of Lactobacillus bacteria growing on nanogel containing culture medium is about 170 cfu/ml and on polymer containing culture medium is only 6 cfu/ml.     

Preparation and characterization of poly(2-acrylamido-2-methylpropane-sulfonic acid)/Chitosan hydrogel using gamma irradiation and its application in wastewater treatment

Radiation grafting of chitosan with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) has been successfully performed. The effect of absorbed dose (kGy) and the chitosan:AMPS ratio on graft hydrogelization was studied. The structure of the prepared hydrogel was confirmed using infrared spectroscopy (IR). Thermal properties were simultaneously studied by thermogravimetric analysis (TGA). The effect of the polymerization variables on the swelling % of the prepared hydrogel was investigated. The highest equilibrium degree of swelling (38.6 g/g) and gel % (94.7%) of the prepared chitosan–AMPS hydrogel was at 40% AMPS and absorbed dose of 10 kGy. The removal of methylene blue, acid red dye, Cd (II) and Cr (III) from composed wastewater was also investigated. The effect of pH, the chitosan:AMPS ratio and the concentration of the pollutant on the adsorption process were studied.     

Characteristics study of clear polymethylmethacrylate dosimeter,Radix W,in several kGy range

Basic characteristics of Radix W, a commercially available undyed polymethylmethacrylate (PMMA) dosimeter conventionally used by readout at 320 nm, were studied in the dose range of 0.5–8 kGy, for its wide application especially for the evaluation of the sterilization dose and the quality assurance of food irradiation. The characteristics of dose response, the effect of irradiation temperature, and its stability after irradiation were examined over candidate readout wavelengths of 270–320 nm. The dose response readout at shorter wavelength is higher than that at longer wavelength, and 280 nm is the suitable readout wavelength for measurement of dose range of 0.5–8 kGy. The post-irradiation stability of dose response for 6 kGy is less than 1% within 24 h after irradiation at an irradiation temperature of 20 °C. Dose response is higher with temperature at irradiation temperatures in the range of −40 to 20 °C.     

Degradation of chlorophenols in aqueous solution by γ-radiation

Degradation of chlorophenols (CPs) in aqueous solutions by γ-radiation was studied. The effect of absorbed dose on degradation, dechlorination and mineralization of CPs were investigated. The results indicated that the degradation of CPs, Cl⁻ release and mineralization increased with increase in absorbed dose. When the initial concentration was 100 mg L⁻¹ and the dosage was 6 kGy, the removal efficiencies of CPs were 44.54% for 2-CP, 91.46% for 3-CP, 82.72% for 4-CP and 93.25% for 2,4-DCP, respectively. The combination of irradiation and H₂O₂ leads to a synergistic effect, which remarkably increased the degradation efficiency of CPs and TOC removal. The kinetics of CPs during irradiation are also mentioned.     

Oxygen selective ceramic hollow fiber membranes

Oxygen ion conducting Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ hollow fiber membranes with o.d. 1.15 mm and i.d. 0.71 mm were fabricated using a sequence of extrusion, gelation, coating and sintering steps. The starting ceramic powder was synthesized by combined EDTA–citrate complexing followed by thermal treatment at 900 °C. The powder was then dispersed in a polymer solution, and extruded through a spinerette. After gelation, an additional thin coating of the ceramic powder was applied on the fiber, and sintering was carried out at 1190 °C to obtain the final ceramic membrane. The fibers were characterized by SEM, and tested for air separation at ambient pressure and at temperatures between 700 and 950 °C. The maximum oxygen flux measured was 5.1 mL/min/cm² at 950 °C.     

Effects of gamma irradiation on chemical,microbial quality and shelf life of shrimp

In the present study the combined effect of gamma irradiation (1, 3 and 5 kGy) and storage at two temperatures: refrigeration (+4 °C) and frozen (?18 °C), on the shelf-life extension of fresh shrimp meat was investigated. The study was based on microbiological and physicochemical changes occuring in the shrimp samples. Total volatile base nitrogen values and trimethylamine values for irradiated shrimp samples were significantly lower than non-irradiated samples at both storage temperatures, and the rate of decrease was more pronounced in samples irradiated at the higher dose (p<0.05). Thiobarbituric acid values for irradiated shrimp samples were significantly higher than non-irradiated samples at both storage temperatures (p<0.05). pH values of shrimp samples were affected significantly by both irradiating dose and storage temperatures (p<0.05). Microbial counts for non-irradiated shrimp samples were higher than the respective irradiated samples at both storage temperatures (p<0.05). The results revealed that irradiation at high dose (5 kGy) might enhance lipid oxidation, although the growth of microorganisms and protein oxidation was inhibited.     

Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N₂ atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm^?3.     

A novel polymeric electrolyte based on a copolymer containing self-assembled stearylate moiety for lithium-ion batteries

A novel polymeric electrolyte based on a self-assembled copolymer moiety has been prepared by a simple method of photo-induced radical polymerization of a mixture consisting of stearylmethacrylate (SMA) and poly(ethylene glycol)-monomethacrylate (PEM) that dissolves LiBF₄ as the electrolytic salt. The SMA moiety work as mechanically stable backbone and the PEM unit dissolving the salts serves as ion-conducting path in the polymeric composite. Solid-state NMR measurements indicated that the resulting polymer composite consists of PEM-rich and SMA-rich phases, each of which exists within several nanometers apart. The ionic conductivity of the polymer electrolyte with the composition of PEM/SMA = 7/3 (by mass ratio) was 2.8 × 10^?5 S cm^?1 at 50 °C, which was significantly higher than that of the polymer electrolyte based on cross-linked PEM copolymer without SMA.     

Effect of gamma irradiated sodium alginate on red amaranth (Amaranthus cruentus L.) as growth promoter

In order to study the growth promotion behavior of sodium alginate (SA) on vegetable (red amaranth, Amaranthus cruentus L.), 3% aqueous solution of SA was irradiated by γ-radiation (Co-60) of various total doses (12.5–50.0 kGy) at a dose rate of 3.5 kGy/h. Viscosity of the irradiated SA was found to decrease with increase in the radiation dose. The average molecular weight was also decreased from 10⁴ to 10³ orders. Red amaranth was cultivated in 18 different individual plots and SA solution (150 ppm) was applied on red amaranth after 10 days of seedlings at every 6 days interval. The morphological characters of vegetables were studied randomly in different unit plots. The irradiated SA of 37.5 kGy at 150 ppm solution showed the best performance. Dry matter of red amaranth significantly increased at 37.5 kGy of irradiated alginate treatment which was about 50% higher than that of the untreated samples. The effect of SA on red amaranth was found significant increase; i.e. plant height (17.8%), root length (12.7%), number of leaf (5.4%) and maximum leaf area (2%) compared to that of the control vegetative plant production.     

A mild method of amine-type adsorbents syntheses with emulsion graft polymerization of glycidyl methacrylate on polyethylene non-woven fabric by pre-irradiation

A mild pre-irradiation method was used to graft glycidyl methacrylate (GMA) onto polyethylene (PE) non-woven fabric (NF). The polymer was irradiated by electron beam in air atmosphere at room temperature. The degree of grafting (D_g) was determined as a function of reaction time, absorbed dose, monomer concentration and temperature. After 30 kGy irradiation, with 5% GMA, surfactant Tween 20 (Tw-20) of 0.5% at 55 °C for 15 min, the trunk polymer was made grafted with a D_g of 150%. Selected PE-g-PGMA of different D_g was modified with aminated compounds such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA). The obtained amine-type adsorbents were prepared to remove copper and uranium ions from solution. It was shown that at least 90% of copper and 60% of uranium with the initial concentration from 3 to 1000 ppb can be removed from water.     

Advanced oxidation of aromatic VOCs using a pilot system with electron beam–catalyst coupling

The decomposition of volatile organic compounds (VOCs) using a pilot system of electron beam (EB)–catalyst coupling was investigated. Two aromatic VOCs, toluene (1800 ppmC) and o-xylene (1500 ppmC), were irradiated with a dose range of 0–10 kGy at room temperature. The removal efficiencies for toluene and o-xylene were 92.4% and 94.5%, respectively, under a 10 kGy absorbed dose condition, which were higher than the results of 45.7% and 52.3% when EB-only was used, respectively. The CO₂ selectivity approached 100% for both toluene and o-xylene using the EB-catalyst coupling system, while the concentrations of O₃ formed were 0.02 ppm (toluene) and 0.003 ppm (o-xylene) at 10 kGy. The aerosol concentration was also measured as 43.2 μg/m³ (toluene) and 53.4 μg/m³ (o-xylene) at 10 kGy absorbed dose.     

Radioactivity level of soil around Baqiao coal-fired power plant in China

Natural radioactivity level of soil around Baqiao coal-fired power plant in China was determined using gamma ray spectrometry. The concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied soil samples range from 27.6 to 48.8, 44.4 to 61.4 and 640.2 to 992.2 Bq kg^?1 with an average of 36.1, 51.1 and 733.9 Bq kg^?1, respectively, which are slightly higher than the average values of Shaanxi soil. The radium equivalent activity, the air absorbed dose rate and the annual effective dose rate were calculated and compared with the internationally reported or reference values. The radium equivalent activities of the studied samples are below the internationally accepted values. The air absorbed dose rate and the annual effective dose rate received by the local residents due to the natural radionuclides in soil are slightly higher than the mean value of Xi'an and worldwide.     

Near-infrared spectroscopy as an effective tool for monitoring the conformation of alkylammonium surfactants in montmorillonite interlayers

Application of near-infrared (NIR) spectroscopy to probing the arrangement of trimethylalkylammonium cations in montmorillonite interlayers has been demonstrated. Detailed analysis of the mid-IR (MIR) and NIR spectra of montmorillonite from Jelšový Potok (JP, Slovakia) saturated with surfactants with varying alkyl chain length (even numbers of carbon atoms from C6 to C18) was performed to show the advantages of the NIR region in characterizing surfactant conformations. The position of the ν_as(CH₂), (∼2930–2920 cm⁻¹), ν_s(CH₂) (∼2860–2850 cm⁻¹), 2ν_as(CH₂) (∼5810–5785 cm⁻¹), (ν + δ)_as(CH₂) (∼4340–4330 cm⁻¹) and (ν + δ)_s(CH₂) (∼4270–4250 cm⁻¹) signals was used as an indicator of the gauche/trans conformer ratio. For all bands, a shift toward lower wavenumber on increasing the alkyl chain length from 6 to 18 carbons suggests a transition from disordered liquid-like to more ordered solid-like structures of the surfactants. The magnitude of the shift was significantly higher for 2ν_as(CH₂) (28 cm⁻¹) than for ν_as(CH₂) (8 cm⁻¹) or ν_s(CH₂) (10 cm⁻¹), showing the NIR region to be a useful tool for examining this issue. Comparison of the IR spectra of crystalline alkylammonium salts and the corresponding organo-montmorillonites demonstrated a confining effect of montmorillonite layers on surfactant ordering. For each alkyl chain length the CH₂ bands of the organo-montmorillonites appeared at higher wavenumbers than for the unconfined surfactant, thus indicating a higher disorder of the alkyl chains. The wavenumber difference between corresponding samples was always higher in the NIR than in the MIR region. All these findings show NIR spectroscopy to be useful for conformational studies.