Showing papers in "Radiation Physics and Chemistry in 2007"

Production of low-energy electrons by ionizing radiation

Abstract: Low-energy electrons are involved in almost all of the physical, physico-chemical and chemical phenomena underlying radiation chemistry and play a central role in determining the effects of ionizing radiation chemistry. A detail quantitative description of their production is desirable, but not available in even the simplest liquids. The distribution defining the cascade of low-energy electrons produced in the radiolysis of liquid water is characterized. The most probable energy and mean energy for secondary electron produced by a primary ion are ∼ 9 – 10 and 50–60 eV, respectively, depending on the specific energy of the primary ion. The energy spectrum of the sub-excitation electrons produced by attenuation of all electrons to 25 eV is determined, and its mean is also 9 eV.

Synthesis of silver nanoparticles by γ-ray irradiation in acetic water solution containing chitosan

Abstract: Silver nanoparticles were synthesized by γ -ray irradiation of acetic water solutions containing AgNO 3 and chitosan. The resulting particles with the average diameter of 4–5 nm were densely dispersed in the solution due to the protection of chitosan chains. UV–vis spectra showed that the irradiation dose would affect the size distribution of nanoparticles.

Monte Carlo treatment planning for photon and electron beams

Abstract: During the last few decades, accuracy in photon and electron radiotherapy has increased substantially. This is partly due to enhanced linear accelerator technology, providing more flexibility in field definition (e.g. the usage of computer-controlled dynamic multileaf collimators), which led to intensity modulated radiotherapy (IMRT). Important improvements have also been made in the treatment planning process, more specifically in the dose calculations. Originally, dose calculations relied heavily on analytic, semi-analytic and empirical algorithms. The more accurate convolution/superposition codes use pre-calculated Monte Carlo dose “kernels” partly accounting for tissue density heterogeneities. It is generally recognized that the Monte Carlo method is able to increase accuracy even further. Since the second half of the 1990s, several Monte Carlo dose engines for radiotherapy treatment planning have been introduced. To enable the use of a Monte Carlo treatment planning (MCTP) dose engine in clinical circumstances, approximations have been introduced to limit the calculation time. In this paper, the literature on MCTP is reviewed, focussing on patient modeling, approximations in linear accelerator modeling and variance reduction techniques. An overview of published comparisons between MC dose engines and conventional dose calculations is provided for phantom studies and clinical examples, evaluating the added value of MCTP in the clinic. An overview of existing Monte Carlo dose engines and commercial MCTP systems is presented and some specific issues concerning the commissioning of a MCTP system are discussed.

Preparation of oligochitosan stabilized silver nanoparticles by gamma irradiation

Abstract: Size tunable and biocompatible silver nanoparticles were prepared by γ irradiation using oligochitosan [ ( GlcN ) x ] as stabilizer, the average particle size was between 5 and 15 nm. Owing to the protonation of the ( GlcN ) x shell, the silver nanoparticles were stable at pH between 1.8–9.0, as characterized by zeta potential measurements and transmission electron micrography (TEM). The nanoparticles are stable in NaCl solution; but NaNO3 or NaH2PO4 cause their aggregation.

Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

Abstract: The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks.

Effect of radiation processing on antinutrients, in-vitro protein digestibility and protein efficiency ratio bioassay of legume seeds

Abstract: The effects of irradiation (dose levels of 5, 7.5 and 10 kGy) on nutritive characteristics of peas ( Pisum satinum L), cowpeas ( Vigna unguiculata L.Walp), lentils ( Lens culinaris Med), kidneybeans ( Phaseolus vulgaris L), and chickpeas ( Cicer arietinum L) were examined. Analyses included proximate composition, levels of anti-nutrients (phytic acid, tannins), available lysine (AL), in vitro protein digestibility (IVPD), and protein efficiency ratio (PER) in the growing rat. The results showed that moisture, crude protein, crude fat, crude fiber, and ash were unchanged by the irradiation. Radiation processing significantly ( p

Radiation grafting of styrene onto polypropylene fibres by a 10 MeV electron beam

Abstract: The radiation-induced graft copolymerization is an effective method for modification of the chemical and physical properties of polypropylene. Graft copolymerization of styrene onto polypropylene fibers has been studied by simultaneous irradiation method, using a 10 MeV electron beam. Samples were irradiated in an environment of nitrogen gas. The effects of radiation dose and styrene concentration in methanol, on the grafting yield were investigated. The effects of polyfunctional monomer, i.e., trimethylopropane trimethacrylate (TMPTMA) and acid (sulfuric acid) on the grafting yield were also examined. The grafted samples were then sulfonated and allowed to react with solution of a basic dye. The samples were characterized by mechanical properties and thermal stability. The mechanical properties of the radiated samples were reduced and the grafted samples had lower mechanical properties.

Radiation treatment for sterilization of packaging materials

Abstract: Treatment with gamma and electron radiation is becoming a common process for the sterilization of packages, mostly made of natural or synthetic plastics, used in the aseptic processing of foods and pharmaceuticals. The effect of irradiation on these materials is crucial for packaging engineering to understand the effects of these new treatments. Packaging material may be irradiated either prior to or after filling. The irradiation prior to filling is usually chosen for dairy products, processed food, beverages, pharmaceutical, and medical device industries in the United States, Europe, and Canada. Radiation effects on packaging material properties still need further investigation. This paper summarizes the work done by different groups and discusses recent developments in regulations and testing procedures in the field of packaging technology.

Degradation of chlorophenols in aqueous solution by γ-radiation

Abstract: 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 H 2 O 2 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.

Influence of diluent on radiolysis of amides in organic solution

Abstract: The radiolytic behavior of N,N,N′,N′-tetraoctyldiglycolamide, N,N′-dimethyl-N,N′-dioctyl-2-(3′-oxapentadecyl)malonamide, and N,N-dioctylhexanamide in n-dodecane was investigated by irradiation with γ-rays and electron pulses The results showed n-dodecane has a sensitization effect on the radiolysis of these amides, owing mainly to a charge transfer from radical cations of n-dodecane to the amide molecules in the primary process observed in pulse radiolysis This result was supported by the difference in the ionization potentials between n-dodecane and these amides

Development of honey hydrogel dressing for enhanced wound healing

Abstract: Radiation at 25 and 50 kGy showed no effect on the acidic pH of the local honey, Gelam, and its antimicrobial property against Staphylococcus aureus but significantly reduced the viscosity. Honey stored up to 2 years at room temperature retained all the properties studied. Radiation sterilized Gelam honey significantly stimulated the rate of burn wound healing in Sprague-Dawley rats as demonstrated by the increased rate of wound contraction and gross appearance. Gelam honey attenuates wound inflammation; and re-epithelialization was well advanced compared to the treatment using silver sulphadiazine (SSD) cream. To enhance further the use of honey in wound treatment and for easy handling, Gelam honey was incorporated into our hydrogel dressing formulation, which was then cross-linked and sterilized using electron beam at 25 kGy. Hydrogel with 6% of honey was selected based on the physical appearance.

Effect of different dose gamma radiation and refrigeration on the chemical and sensory properties and microbiological status of aqua cultured sea bass ( Dicentrarchus labrax)

Abstract: Quality and shelf life of non-irradiated and irradiated (2.5 and 5 kGy) sea bass in ice conditions and stored at + 4 ∘ C were investigated by measurement in microbiological, chemical sensory analyses. Microbial counts for non-irradiated sea bass samples were higher than irradiated fish. Among chemical indicators of spoilage, total volatile base nitrogen (TVB-N) values increased to 36.44 mg/100 g for non-irradiated sea bass during iced storage, whereas for irradiated fish lower values of 25.26 mg/100 g and 23.61 mg/100 g were recorded at 2.5 and 5 kGy, respectively (day 17). Trimethylamine (TMA-N) values and thiobarbituric acid (TBA) values for irradiated samples were lower than that for non-irradiated samples. Acceptability scores for odour, taste and texture of cooked sea bass decreased with storage time. The sensory scores of sea bass stored in control and 2.5–5 kGy at + 4 ∘ C were 13 and 15 days, respectively. The results obtained from this study showed that the shelf life of sea bass stored in ice, as determined by overall acceptability of all data, is 13 days for non-irradiated sea bass and 15 days for 2.5 kGy irradiated and 17 days for 5 kGy irradiated sea bass.

Anti-aging and aging factors in life. The role of free radicals

Abstract: The present review deals with some factors determining the anti-aging as well as the aging process. In order to get a deeper insight in the subject matter, firstly some less known spectroscopic and kinetic data of antioxidant vitamins (C, E, β-carotene) acting as anti-aging factors by electron transfer are briefly discussed. The generation of oxygen transients (OH, ROO, 1O2, ozone radicals, etc.) by sunlight, ultrasonic and microwave radiation are causing “oxygen stress” and contribute to early ageing is also reviewed. Particular attention is paid to external environmental aging factors. Their action is based on the incorporation of various pollutants contained in water and air in the human organism. In this respect the polycyclic aromatic hydrocarbons (PAHs) play an essential role by initiating DNA-mutation, leading to an accelerate aging, carcinogenesis and diseases.

Synthesis of silver nanoparticles supported on silica aerogel using gamma radiolysis

Abstract: Silver clusters on SiO 2 support have been synthesized using 60 Co gamma radiation. The irradiation of Ag + in aqueous suspension of SiO 2 in the presence of 0.2 mol dm −3 isopropanol resulted in the formation of yellow suspension. The absorption spectrum showed a band at 408 nm corresponding to typical characteristic surface plasmon resonance of Ag nanoparticles. The effect of Ag + concentration on the formation of Ag cluster indicated that the size of Ag clusters vary with Ag + concentration, which was varied from 4×10 −4 to 5×10 −3 mol dm −3 . The results showed that Ag clusters are stable in the pH range of 2–9 and start agglomerating in the alkaline region at pH above 9. The effect of radiation dose rate and ratio of Ag + /SiO 2 on the formation of Ag clusters have also been investigated. The prepared clusters have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which showed the particle size of Ag clusters to be in the range of 10–20 nm.

Surface modification of microfluidic channels by UV-mediated graft polymerization of non-fouling and ‘smart’ polymers

Abstract: Microfluidic channels prepared from polydimethylsiloxane (PDMS) have been modified by UV-mediated graft polymerization of temperature-responsive polymers (poly[N-isopropyl acrylamide] or pNIPAAm), temperature- and pH-responsive copolymers (P[NIPAAm-co-acrylic acid (AAc)]), and a non-fouling hydrogel (polyethyleneglycol diacrylate, or PEGDA). This was done by presorbing a photosensitizer (PS) within the PDMS channel surface regions, contacting the different monomer solutions with the PS-containing surface under nitrogen, and irradiating with UV. The pNIPAAm-grafted surface was hydrophilic below its lower critical solution temperature (LCST), resisting non-specific adsorption, while it was hydrophobic above its LCST, now binding pNIPAAm-coated nanoparticles. Combined temperature- and pH-responsive surfaces were also prepared by UV radiation grafting a monomer mixture of pNIPAAm with AAc. The surfaces have been characterized by advancing water contact angle measurements. These smart microfluidic channels should be useful for many applications such as affinity separations and diagnostic assays.

The changes of fatty acid and amino acid compositions in sea bream (Sparus aurata) during irradiation process

Abstract: Aqua cultured fish (sea bream) were irradiated by Cobalt-60 at commercial irradiation facility at dose of 2.5 and 5 kGy at 2–4 °C. The proximate composition, fatty acid and amino acid composition changes of irradiated aqua cultured sea bream ( Sparus aurata ) of Aegean Sea were investigated. Total saturated (28.01%) and total monounsaturated (28.42%) fatty acid contents of non-irradiated decreased content of 27.69–27.97% for 2.5 kGy irradiated groups and increased content of 28.33–28.56% for 5 kGy irradiated groups after irradiation process. Total polyunsaturated fatty acid content for irradiated samples was lower than that of non-irradiated samples. Aspartic acid, glutamic acid, serine, glycine, arginine, alanine, tyrosine, cystine, tryptophan, lysine and proline contents for 2.5 and 5 kGy irradiated sea bream are significantly different ( p

Biodegradability enhancement of textile wastewater by electron beam irradiation

Abstract: Textile wastewater generally contains various pollutants, which can cause problems during biological treatment. Electron beam radiation technology was applied to enhance the biodegradability of textile wastewater for an activated sludge process. The biodegradability (BOD5/COD) increased at a 1.0 kGy dose. The biorefractory organic compounds were converted into more easily biodegradable compounds such as organic acids having lower molecular weights. In spite of the short hydraulic retention time (HRT) of the activated sludge process, not only high organic removal efficiencies, but also high microbial activities were achieved. In conclusion, textile wastewater was effectively treated by the combined process of electron beam radiation and an activated sludge process.

Degradation of diazinon contaminated waters by ionizing radiation

Abstract: Study of degradation of diazinon pesticide by 60Co gamma irradiation in a single aqueous solution was conducted on a laboratory scale and the effect of ionizing radiation on the removal efficiency of diazinon residues was investigated. Distilled water solutions at three different concentrations of targeted compound (i.e. 0.329, 1.643 and 3.286 μmol dm−3) were irradiated over the range 0.1–6 kGy. The initial concentration of contaminant and irradiation doses play a significant role in the rate of destruction; this was evident from the calculated decay constants of diazinon residue. Gamma radiolysis showed that the absorbed doses from 1.5 to 5.6 kGy at a dose rate of 4.79 kGy h−1 achieved 90% destruction for diazinon with initial concentrations over the range 0.329–3.286 μmol dm−3. The radiolytic degradation by-products and their mass balances were qualitative determined with good confidence by using GC/quadrupole mass spectrometry (GC/MS) with EI+ or CI in positive and negative ionization mode and diazinon degradation pathways were proposed. Additionally, the final products of irradiation were identified by ion chromatography (IC) to be acetic and formic acid.

Effects of gamma radiation on total phenolics, trypsin and tannin inhibitors in soybean grains

Abstract: The objective was determining possible radiation-induced alterations (with doses of 2, 4 and 8 kGy) in raw or cooked grains from five soybean cultivars through the analysis of some antinutrient. Total phenolic ranged from 2.46 to 10.83 mg/g, the trypsin inhibited from 18.19 to 71.64 UTI/g and tannins from 0.01 to 0.39 mg/g. All the antinutrient studied underwent reduction with increases in the doses and cooking process was effective too.

Chemical-radiation degradation of natural oligoamino-polysaccharides for agricultural application

Abstract: The main objective of the research was to elaborate the method of degradation of natural aminopolysaccharides to obtain a product applicable as biospecimen in protection and stimulation of the plants growth. Depolymerization of chitosan can be carried out by radiation or chemical degradation combined with irradiation method. The efficiency of these methods was verified by viscometric analysis. The chemical-radiation method was much more appropriate from economical point of view. By application of this method it was possible to obtain product with lower crystalline phase content than initial one, what was proved by X-ray diffraction studies. Finally preliminary agricultural tests on spring rape seeds were performed. The results show that the biggest growth was observed for chitosan (molecular weight 47,000 Da) in concentration of 0.1 g/kg of seeds. The higher concentration did not affect plant's growth. The average growth over-ground plant parts was about 16–22%, diameter of roots was about 11–13%, and mass of roots was about 51–65% higher in comparison to the control.

Theoretical aspects of energy–range relations, stopping power and energy straggling of protons

Abstract: The Bragg–Kleeman rule R CSDA = AE 0 p provides a connection between the initial energy E 0 of a proton and the range R CSDA in a medium, if the continuous-slowing-down approximation (CSDA) is assumed. The rule results from a generalized (nonrelativistic) Langevin equation; its integration also yields information on the residual energy E ( z ) or d E ( z ) / d z of a proton at position z. A relativistic extension of the generalized Langevin equation leads to the formula R CSDA = A ( E 0 + E 0 2 / 2 Mc 2 ) p . Since the initial energy E 0 of therapeutic protons satisfies E 0 ⪡ 2 Mc 2 , relativistic contributions can be treated as correction terms. Besides this phenomenological aspect, a complete integration of Bethe–Bloch equation (BBE) is presented, which provides the determination of R CSDA , E ( z ) , d E ( z ) / d z and works without any empirical parameters. The results of these different methods are compared with Monte Carlo calculations (GEANT4). Since the energy transfer from proton to the environmental atomic electrons regarded in the CSDA-framework has to account for local fluctuations, an analysis of the Gaussian convolution and the Landau–Vavilov distribution function is performed on the basis of quantum-statistical mechanics. The Landau tail can be described as a Hermite polynomial correction of a Gaussian convolution.

Cross-linking of poly(N-vinyl pyrrolidone) films by electron beam irradiation

Abstract: Biocompatible hydrogels based on poly(N-vinyl pyrrolidone) (PVP) were synthesized by electron beam irradiation of the dry polymer under various conditions. Sol–gel analysis of the bulk gel (in mm range) gave a dose of gelation of 94 kGy. As seen for various other polymers, the network density rises with the increase in dose. At around 350 kGy, PVP began to decompose. Based on these observations, films in μm range on a silicon wafer were synthesized by electron beam irradiation. Due to irradiation, the films adhered irreversibly on the wafer. Their swelling behavior was analyzed by ellipsometry.

Kβ/Kα X-ray intensity ratios for elements in the range 16⩽Z⩽92 excited by 5.9, 59.5 and 123.6keV photons

Abstract: The K shell intensity ratios Kβ/Kα for 59 elements in the atomic region 16⩽Z⩽92 have been measured at excitation energies of 5.9, 59.5 and 123.6 keV. K X-rays emitted by samples have been counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. The measured values were compared with the theoretical values calculated using Scofield's tables based on the Hartree–Slater and Hartree–Fock theories and available experimental values. Reasonable agreement is typically obtained between present and theoretical values.

Positronium chemistry in porous materials

Abstract: Porous materials have fascinated positron and positronium chemists for over decades. In the early 1970s it was already known that ortho -positronium ( o -Ps) exhibits characteristic long lifetimes in silica gels, porous glass and zeolites. Since then, our understanding of Ps formation, diffusion and annihilation has been drastically deepened. Ps is now well recognized as a powerful porosimetric and chemical probe to study the average pore size, pore size distribution, pore connectivity and surface properties of various porous materials including thin films. In this paper, developments of Ps chemistry in porous materials undertaken in the past some 40 yr are surveyed and problems to be addressed in future are briefly discussed.

Production of high melt strength polypropylene by gamma irradiation

Abstract: High melt strength polypropylene (HMS-PP) has been recently developed and introduced in the market by the major international producers of polypropylene. Therefore, BRASKEM, the leading Brazilian PP producer, together with EMBRARAD, the leading Brazilian gamma irradiator, and the IPEN (Institute of Nuclear Energy and Research) worked to develop a national technology for the production of HMS-PP. One of the effective approaches to improve melt strength and extensibility is to add chain branches onto polypropylene backbone using gamma radiation. Branching and grafting result from the radical combinations during irradiation process. Crosslinking and main chain scission in the polymer structure are also obtained during this process. In this work, gamma irradiation technique was used to induce chemical changes in commercial polypropylene with two different monomers, Tri-allyl-isocyanurate (TAIC) and Tri-methylolpropane-trimethacrylate (TMPTMA), with concentration ranging from 1.5 to 5.0 mmol/100 g of polypropylene. These samples were irradiated with a 60 Co source at dose of 20 kGy. It used two different methods of HMS-PP processing. The crosslinking of modified polymers was studied by measuring gel content melt flow rate and rheological properties like melt strength and drawability. It was observed that the reaction method and the monomer type have influenced the properties. However, the concentration variation of monomer has no effect.

Water equivalence of polymer gel dosimeters

Abstract: To evaluate the water equivalence and radiation transport properties of polymer gel dosimeters over the wide range of photon and electron energies 14 different types of polymer gels were considered. Their water equivalence was evaluated in terms of effective atomic number ( Z eff ), electron density ( ρ e ), photon mass attenuation coefficient ( μ / ρ ), photon mass energy absorption coefficient ( μ en / ρ ) and total stopping power ( S / ρ ) tot of electrons using the XCOM and the ESTAR database. The study showed that the effective atomic number of polymer gels were very close ( 1 % ) to that of water except PAGAT, MAGAT and NIPAM which had the variation of 3%, 2% and 3%, respectively. The value of μ / ρ and μ en / ρ for all polymer gels were in close agreement ( 1 % ) with that of water beyond 80 keV. The value of ( S / ρ ) tot of electrons in polymer gel dosimeters were within 1% agreement with that of water. From the study we conclude that at lower energy ( 80 keV ) the polymer gel dosimeters cannot be considered water equivalent and study has to be carried out before using the polymer gel for clinical application.

Effect of low-dose γ-irradiation on the shelf life and quality characteristics of minimally processed potato cubes under modified atmosphere packaging

Abstract: The processing conditions involving γ-irradiation for minimally processed potato cubes were optimized by response surface methodology. The effect of γ-irradiation dose (0–1.5 kGy), citric acid concentration (0–1.0%), KMS concentration (0–1.0%) and their complex interaction on L, a, b value, hardness and total sugar content were studied using a central composite rotatable design of experiments. The results showed that at the optimum conditions (γ-irradiation dose 1.0 kGy; citric acid concentration 0.33% and KMS concentration 0.55%) the L-value was ⩾48.50%, a-value ⩽0.95, b-value ⩽7.5, hardness ⩾100 N, sucrose concentration ⩽0.19% and sensory score ⩾6.0 at the end of the storage period of 4 weeks.

Effect of electron-beam and gamma-irradiation on physicochemical and mechanical properties of polypropylene syringes as a function of irradiation dose: Study under vacuum

Abstract: The effect of electron-beam and gamma irradiation under vacuum on the physicochemical and mechanical properties of commercial polypropylene (PP) syringes was studied. Irradiation doses of 30, 60 and 120 kGy were used while for comparison purposes respective non-irradiated (control) PP syringes were also studied. Mechanical tests, differential scanning calorimetry analysis, color determination and FTIR were carried out to evaluate the effect of both irradiation treatments (electron-beam and gamma irradiation) on PP syringes. Both compression strength and % extension at break decreased with increasing irradiation dose. Melting temperature as well as specific melting enthalpy also decreased while the degree of yellowness increased with increasing irradiation dose. Minor differences in FTIR spectra were observed after irradiation treatment.

Thermal and crystallization behaviour of gamma irradiated PLLA

Abstract: Structure, crystallization behaviour and some thermal properties of poly- l -lactide (PLLA), gamma irradiated up to 300 kGy, have been studied Through differential scanning calorimetry measurements, radiation-induced changes were evident in the enthalpy of melting and cold crystallization, as well as in the degree of crystallinity Decay of the glass transition, cold crystallization and melting temperatures with irradiation dose was observed in all cases The annealing treatment, which can substantially reduce the concentration of free radicals, also had a great impact on thermal/crystallization behaviour of irradiated PLLA Extensive chain scission, as a dominant effect of gamma irradiation, confirmed by gel permeation chromatography, has as a consequence a growth of new thin crystal lamellae and occurrence of the second low-temperature melting peak Thermogravimetric analyses have shown that irradiation lowered the thermal stability of PLLA

Preparation and characterization of a novel IPN hydrogel memberane of poly( N-isopropylacrylamide)/carboxymethyl chitosan (PNIPAAM/CMCS)

Abstract: A novel type of interpenetrating polymer networks (IPN) hydrogel membrane of poly( N -isopropylacrylamide)/carboxymethyl chitosan (PNIPAAm)/(CMCS) was prepared, and the effects of the feed ratio of components, swelling medium and irradiation dose on the swelling and deswelling properties of the hydrogel was systematically studied. The results showed that the introduction of CMCS did not shift the LCST (at 32 °C), which is similar to the pure PNIPAAm. The lowest swelling ratio was at pH 2. There was little influence of irradiation dose on the thermo- and pH-sensitivity of the IPN hydrogel, increasing dose only decreased the swelling ratio. The PNIPAAm:CMCS=1:4 w/w hydrogel was not thermo-sensitive in distilled water, whereas it showed a discontinuous volume phase transition in pH 2 and a continuous one in pH 8 buffer. Consequently, a combination of pH and temperature can be coupled to control the responsive behavior of these hydrogels.