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Association of two chitosans of different degrees of acetylation (DA) is studied in dilute water/acid/salt solutions by combined analysis of static and dynamic light scattering. The influence of sodium salt anions Cl − and CH 3 COO − on conformation of macromolecules and properties of clusters was studied. At DA = 15 mol%, the macromolecules exist either in rigid-rod (R g /R h = 2.7) or in coil (R g /R h = 1.8) conformations in the solvents containing NaCl and CH 3 COONa, respectively. Chitosans with higher DA = 28% dissolved in the solvent containing CH 3 COONa are in the collapsed state (R g /R h < 0.8), predicted by Dobrynin (Macromolecules, 2004). The clusters are of spherical form (0.8 < R g /R h < 1.2). CH 3 COONa promotes higher fractal dimensionality of clusters (2.2-2.4) than NaCl (1.9). Higher critical aggregation concentration is observed in NaCl. The other hydrodynamic methods (capillary viscometry, velocity sedimentation, and Tsvetkov diffusometry) do not detect the clusters, probably, because of their disruption during flow.

Considerable progress in the development of new materials is achieved due to the modification of polymer materials by carbon nanoparticles of various kinds. In this work new composites of nanodiamonds (ND) and poly (phenylene oxide) (PPO) were prepared by solid phase dispersing. Their solutions and dense nonporous films were studied by different techniques. The structure of the PPO/ND composites was examined by atomic force microscopy, dynamic light scattering, and birefringence. The increase of ND content in the film leads to a more complex structure because of accumulation of aggregates containing ND particles and PPO molecules. The physical and mechanical properties were exhaustively evaluated by measuring intrinsic viscosity, density, surface tension, the Young's modulus, yield stress, tensile strength, and ultimate strain. Gas transport properties were determined by measuring H2, CO2, N2, CH4, and O2 permeation. The gas permeability coefficients decrease slightly with an increase of the ND content in composites, but the ideal selectivity of gas separation increases at the same time. POLYM. COMPOS., 39:3952–3961, 2018. © 2017 Society of Plastics Engineers

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