The aim of the study was to determine whether it is possible to correlate directly the barrier properties of elastomer materials assessed on the basis of the breakthrough time t_{p} with the thermodynamic affinity of the elastomer-solvent system, characterized by their solubility parameters δ. According to EN ISO 6529:2001 standard, breakthrough time is defined as the time elapsing from the moment that the tested material sample gets in contact with the chemical to the moment in that a specified amount of the substance appears on the other side of the sample. Cured butyl rubber (IIR) in the form of flat membranes were tested in the study. For the nonpolar rubber-polar or rubber-nonpolar solvent systems it has been found that significant differences in rubber and solvent solubility parameters not in every case leads to better resistance to permeation. The properties of the permeating chemical and the rubber, including its polarity, shape, and molecule dimension of the solvent, are of considerable importance. A marked disparity of breakthrough times were observed for the permeation of polar or nonpolar solvents despite similar values of their solvent solubility parameter. The breakthrough time of the solvent from the homologous series (pentane, hexane and heptane) is determined not only by the rubber and solvent solubility parameters but by the size of the chemical molecule as well. Therefore, for the assessment of material barrier properties the thermodynamic affinity or dissimilarity of the elastomer and the permeating solvent is only semiquantitative in character.
Gas barrier properties of polymeric membranes with different rigidness of their matrix where studied by gas phase permeation measurements. Gas transport results in membranes made of epoxy resin with different cross linking densities and epoxy resin with dispersed few layer graphene fillers were discussed and compared in the framework of the free volume theory of diffusion. Transport in cellulose membranes was found to occur in the diffusion configurational regime. The physical description of the transport properties was based on positron annihilation lifetime spectroscopy measurements which allowed to evaluate experimentally the fractional free volume in epoxy resin membranes and the size of rigid elongated cavities in cellulose thin films.
Network properties of ureasil-based polymer matrixes suitable for construction of amperometric biosensors were probed by positron annihilation lifetime spectroscopy and swelling experiments. Temperature dependences of the ortho-positronium (o-Ps) lifetimes and their relative intensities were measured in a temperature range of 15-350 K. Glass transition temperatures and expansion coefficients of microscopical free-volume for the investigated polymers were determined. Differences in network behavior for the aged samples and the effect of chalcogenide (As₂S₃) particles on the free volume of ureasil network were observed. Swelling experiments using ethyl alcohol showed that the structure of the aged sample network had less swelling ability for the pure ureasil as well as composite. This suggests that the one of factors influencing swelling is the change of the basic ureasil network due to ageing. It is supposed that the network properties obtained by positron annihilation lifetime spectroscopy and swelling experiments could be very helpful to understand better the bio-functionality of the constructed biosensor based on the ureasil-chalcogenide glass composite.
The beta irradiation, as one of several possibilities how to modify the polymer properties resulted in isotactic polybutene-1 (PB-1) and its random copolymers with ethylene (E) mainly in chain scission without chain cross-linking. The original phase I did not change by irradiation, only the transformation rate of phase II to I increased with the irradiation dose and ethylene groups in PB-1/E copolymers. Beta irradiation decreased the sample crystallinity, crystal size, and perfection.
A simple and fast approach to the design and production of new hybrid polymeric biomaterials with silver particles is presented in this work. Silver/semi-interpenetrating network hybrid hydrogels (Ag/semi-IPNHHs) were prepared through an optimized solution crosslinking copolymerization of 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA), in the presence of PVP, a silver salt and a reducing "green" agent (Ag/P(HEMA/IA)/PVP). PVP was chosen due to its protective, reduction, and nucleation properties in the production of metal particles. The structure of the Ag/semi-IPNHH was characterized by Fourier transform infrared spectroscopy (FTIR). The presence of silver and PVP in the network was confirmed by FTIR spectra. The results obtained by dynamic mechanical analysis (DMA) showed good mechanical properties for all samples. The swelling studies of Ag/P(HEMA/IA)/PVP were conducted in the temperature range of 25-55°C, in the buffer of pH 7.40. The Ag/semi-IPNHH showed temperature-sensitive swelling properties, with the lower critical solution temperature (LCST) values in the physiologically interesting interval. The antimicrobial activity of the samples was tested using E. coli, S. aureus and C. albicans pathogens. It was concluded that the antimicrobial potential depends on the hydrogel's composition and the type of microbes
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