Swelling (and shrinking) of poly(2-vinylpyridine), P2VP, polymer brushes, caused by pH changes, could be readily monitored by transmission surface plasmon resonance, T-SPR, spectroscopy. Gold nanoparticles attached to the P2VP polymer brushes dramatically enhanced the pH-induced shift in the T-SPR absorption spectra. (A 50 nm shift of the absorption maximum of the T-SPR spectrum of the supporting gold nanoislands was observed upon changing the pH from 5.0 to 2.0, corresponding to a swelling of the polymer brushes from 8.1 +/- 0.7 to 24.0 +/- 2.0 nm. Same shift in the opposite direction was observed upon changing the pH from 2.0 to 5.0.)

The present work presents and discusses the interrelation between composition, morphology, thermal history, mechanical and barrier properties to oxygen and limonene of composites of HDPE/ MA-PE/cellulose fibers of significant interest in, among others, food packaging applications. From the overall results, it was observed that increasing the loading of purified alpha-cellulose fibers in the polyethylene matrix beyond 10 wt.% led to a decrease in the permeability coefficient of D-limonene, effect which was found to be primarily related to a decrease in the overall solubility of this strongly plasticizing aroma component. On the other hand, the oxygen permeability was found to decrease to a significant extend with increasing fiber content beyond 5 wt.%, but this effect was more strongly ascribed to a significant decrease in the diffusion coefficient. Therefore, the fibers are thought to generate a more tortuous path for the non-interacting gas molecules to travel across the composites thickness, even when tested at high relative humidity conditions. Optimum fiber loading levels in terms of overall property balance were found to be around 20 wt.%.

Polysaccharides and protein biopolymers are of increasing interest for their use as sustainable film and coating materials. However, their main drawback in these applications is their inherent high water permeability and low water resistance at high relative humidity conditions. In this study, two specifically designed commercial fillers of different nature and aspect ratios were successfully incorporated into two polysaccharides: methyl cellulose and chitosan. The morphology study indicated that a good dispersion with intercalation of the fillers was observed in both matrices. The water barrier properties of the nanobiocomposites were found to be enhanced to a significant extent, particularly for the higher aspect ratio filler, as compared to the pure matrix materials, while the biodegradability of the composite materials was maintained.