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Abstract: Poly(acrylamide) [poly(AAm)] and poly(N-isopropyl-acrylamide) [poly(NIPAAm)] based gel films containing Au nanoparticles (d =14±2.5nm) were synthesized. Monomers and cross-linker were added to a gold nanodispersion, and after the addition of the initiator, polymer films were prepared on the surface of an interdigital microelectrode by photopolymerization. In the course of the syntheses the gold concentration of the films was constant (10.8μg/cm2) and the volume fraction of Au nanoparticles (ϕ Au) in the polymer gel films varied in the range of 0.58–85.3%. Poly(AAm)-based films swell when the temperature increases: due to a temperature shift of 15°C the Au plasmon absorption maximum at λ =∼532nm was shifted towards shorter wavelengths by 16.6nm (blue shift) through the swelling of the polymer gel film. In the case of poly(NIPAAm) the temperature-induced shrinking resulted in a red shift, namely the maximum was shifted by 18.07nm by a temperature shift of 15°C. In the case of both composites, the electric conductivity of the samples was shown to increase with increasing Au particle concentration. In the case of the poly(AAm)-based composite containing ϕ Au =0.85 gold the resistance of the film spread on the surface of the electrode was 0.16MΩ at 25°C and 0.66MΩ at 50°C, i.e. the conductivity of the sample decreased with increasing temperature. The opposite effect is observed in the case of the poly(NIPAAm)-based composite: as temperature is raised, the resistance of the composite abruptly drops at the point of collapse of the NIPAAm gel (it is 0.28MΩ at 32°C and only 0.021MΩ at 35°C). This thermosensitive effect was detectable only at sufficiently high Au contents (ϕ Au =0.85) in both gels. [Copyright &y& Elsevier]

The absorbance in the 190–500 nm range of oxidized lignin-free xylan isolated from unbleached and ozone-bleached hardwood kraft pulps as well as monocarboxyl cellulose in NaOH solution was examined by UV/VIS-spectroscopy and SEC employing multi-wave UV-detection. The first derivative of UV-spectra has been shown to be more useful to investigate the chromophore composition. The chromophore composition of oxypolysaccharides was as follows: carboxyl and carbonyl groups absorbing at 200–220 and 270–290 nm, respectively, heteroaromatics of furan- and pyron-type absorbing additionally at 230–250 and 290–320 nm as well as conjugated heteroaromatics absorbing above 300 nm with maximums at 350–370 and 430–450 nm due to the charge-transfer complexes. Problems regarding the attribution of absorbance to lignin- and heteroaromatics-derived chromophores are discussed. Conjugated heteroaromatic compounds, non-uniformly distributed over MWD, are supposed to be the source for the gel-fraction and contributors to the colour of oxidized polysaccharides. [Copyright &y& Elsevier]