Colloids of metal nanoparticles (NPs) of Au, Ag, Pd, and Pt protected by natural polymer arabinogalactan (ARB) extracted from Larix sibirica were studied. The nanocomposites were prepared by reduction of metal salts in the water solutions of ARB. We carried out dynamic (DLS) and static light scattering resonantly enhanced by the NP plasmons. The translational diffusion was examined via DLS and a polarized interferometer. The virgin ARB was shown to form aggregates in dilute aqueous solutions. The introduction of NPs reduced the size of the virgin ARB aggregates. The aggregate forms as viewed by the scanning electron microscopy support the light scattering results.
The frequency dependence of the shear modulus was studied for cross-linked polyurethane melts and gels at various cross-link densities. The polyurethane used in this study was based on mixtures of bifunctional linear poly(propylene oxide) (PPO) and trifunctional star PPO end-linked with diisocyanate. The connectivity extent was varied by varying the stoichiometric ratio of hydroxyl groups and isocyanate groups. The results were compared with mean field theory predictions. Relaxation of trapped entanglements was observed for almost fully end-linked systems containing a very low concentration of trifunctional PPO.
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