Search results for "IRRADIATION"
showing 10 items of 1012 documents
On the origin of functionalization in one-pot radiation synthesis of nanogels from aqueous polymer solutions
2016
Radiation-engineered poly(N-vinyl pyrrolidone) nanogels are very interesting biocompatible nanocarriers for i.v. administration of therapeutics and contrast agents for bioimaging. The manufacturing process is fast and effective, it grants excellent control of particle size and simultaneous sterilization of the formed nanogels. Interestingly, primary amino groups and carboxyl groups, useful for (bio)conjugation, are also formed in a dose-dependent fashion. In this paper, by means of both numerical simulations and experiments, the origin of nanogel size control and functionalization is investigated. This understanding offers a new dimension for the design and production of radiation-sculpture…
Ejection of molecules from WO3 under ion bombardment: the role of the crystal structure
1992
Abstract Emission of molecular ions from WO 3 and Na x WO 3 was studied by SIMS. It was found that the phenomenon of ejection of molecules had not arisen from specific WO bond lengths and strengths in tungsten trioxide.
Reaktionen bei der Bestrahlung von poly(N-chloramid)en
1980
On irradiating poly(N-chloroamide)s in films or in solution in the range of 325–375 nm carboxamide groups are formed. The irradiated polymer contains chlorine which is linked to C-atoms. This reaction can certainly not be explained with an intramolecular photorearrangement but with a sequence of photoreactions and dark reactions satisfactorily accounting for all observations.
Positrons and electron-irradiation induced defects in the layered semiconductor InSe
1992
The positron annihilation characteristics of the layered semiconductor InSe have been investigated. No evidence for low temperature positron trapping is found in as-grown and heavily deformed InSe. The temperature dependence of the S-parameter in these sample exhibits an increase rate in good agreement with the linear expansion coefficient along the c-axis. The positron lifetime spectra of electron-irradiated 0.01% Sn-doped InSe show a long-lifetime component of 336 ps which is tentatively attributed to positrons trapped at isolated In vacancies. Isochronal annealing experiments performed on these samples show that the recovery of the positron lifetime measured at 77K is accomplished in two…
Radiation synthesis of polyaspartamide functionalised hydrogels for sustained release of fragrances
2005
The aim of the present investigation is to assess the possibility of obtaining a biocompatible material device which is able to deliver oil-soluble fragrances in air over a length of time. Aqueous solutions of polyaspartamide functionalised with glycidyl methacrylate have been cross linked through gamma irradiation in the presence of a lipophilic model fragrance, emulsified prior to irradiation. Two emulsification conditions have been considered at two different concentrations of both fragrance and surfactant in water. Chemical hydrogels have been obtained in correspondence to two irradiation absorbed doses and have been characterised for their solubility properties and swelling ability in …
Chlorine loss from polyvinylchloride under neutron irradiation
1997
PVC samples were irradiated for 1 hour with a thermal neutron flux of Φ th =4.71·1011n·cm−2·s−1 and the chlorine lost during irradiation was measured by γ-ray spectrometry. About 15% of loss of chlorine has been observed for untreated samples while samples heated to temperatures of 60 and 80°C for one minute before irradiation have been found to loose about 8% and 3%, respectively. The results indicate an influence of the polymer structure on the release of chlorine.
Structural modifications in an irradiated ethylene-vinyl alcohol copolymer
1982
Extraction experiments and calorimetric measurements have been performed, on a commercial ethylene-vinyl alcohol copolymer irradiated in the dose range 0–20 Mrad.
Photodegradation of polyglycidol in aqueous solutions exposed to UV irradiation
2011
The photodegradation of polyglycidol in aqueous solution with UV wavelength of 254 nm was investigated. The experiments were carried out in air at a constant temperature and the photodegradation of polyglycidol (PGl) was compared to that of poly(ethylene oxide) (PEO), the most widely studied polyether. Size exclusion chromatography with multiangle light scattering detection (SEC-MALLS) was used to measure the changes in the molar masses and molar mass dispersities of polymers during degradation. The molar mass of PGl decreased dramatically during the first period of UV irradiation and then gradually approached a limiting value of 17,000 g/mol, regardless of the initial polymer concentration…
Photocleavable microcapsules built from photoreactive nanospheres.
2005
We show how photo-cross-linking of nanoparticles within the micrometer-sized thin oil shell of water-oil-water emulsion droplets leads to a new species of optically addressable microcontainers. The inner water droplet of these emulsions may contain drugs, dyes, or other water-soluble components, leading to filled containers. The thickness, mechanical stability, and light resistance of the container walls can be controlled in a simple way by the amount and adjustable photoreactivity of the nanoparticles. Importantly, the chemical bonds between the nanoparticles constituting the microcapsule shell can be cleaved photochemically by irradiation with UV light. This optically controlled destructi…
Elastic Properties of Liquid Crystal Elastomer Balloons
2001
We introduce a method to measure elastic properties of smectic liquid crystalline elastomers. Freely suspended smectic polymer films containing photoreactive groups are inflated to spherical bubbles and crosslinked by UV light irradiation. After crosslinking, the balloon volume is varied and elastic properties of the material are determined from the relation between radius and inner excess pressure. The influence of the network topology on the elastic behaviour is discussed.