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We present a theoretical study of polymer networks, formed by connecting dendritic building blocks (DBB’s). We concentrate on the Rouse dynamics of such networks and perform our study in two steps, considering first single generalized dendrimers (GD’s) and then networks formed by such DBB’s. In GD’s the functionality f of the inner branching points may differ from the functionality f[sub c] of the core. The GD’s cover wide classes of macromolecules, such as the “classical” dendrimers (f[sub c]=f ), the dendritic wedges (f[sub c]=f-1), and the macromolecular stars (f[sub c]>2, f=2). Here we present a systematic, analytic way which allows us to treat the dynamics of individual GD’s. Then, using a general approach based on regular lattices formed by identical cells (meshes) we study the dynamics of GD-based polymer networks. Using analytical and numerical methods we determine the storage and loss moduli, G[sup ′](ω) and G[sup ″](ω). In this way we find that the intradendrimer relaxation domain of G[sup ′](ω) becomes narrower when M[sub cr], the number of connections between the neighboring DBB’s, increases. This effect may be understood due to the exclusion of the longest DBB relaxation times from the spectrum of the network, given that the additional connections hinder the mobility of the peripheral DBB branches. We expect that such effects may be readily observed through appropriate mechanical experiments. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pervaporation is a nonequilibrium membrane process. The pressure or chemical potential gradients are the factors that determine the irreversibility of membrane transfer in pervaporation. In this work, we consider the opportunity of describing and approximating pervaporation data using a nonequilibrium thermodynamic approach. Pervaporation curves for a wide range of feed solution concentrations have been built based on data on a few binary systems. The thermodynamic properties of feed solutions were calculated using vapor–liquid equilibrium data. The sigmoidal Boltzmann function, Gauss function and Praal equation were used to approximate vapor–liquid equilibrium data. Approbation of proposed variants in the construction of pervaporation curves was carried out for five binary systems: ethanol–water at 50°С and 60°С, acetone–water at 30°С, benzene–cyclohexane at 25°С, methanol–methyl-tert-butyl ether at 25°С, and ethanol–butanone at 55°С. The agreement between calculation results and experimental data is in the limits which are sufficient for applied estimations. [ABSTRACT FROM AUTHOR]

• Novel pervaporation PA/fullerene derivative membranes were developed and studied. • Fullerenol, carboxyfullerene and fullerene derivative with arginine were PA modifiers. • Composite membranes increased surface hydrophilicity and swelling in methanol. • Transport properties were evaluated in pervaporation of methanol/toluene mixture. • Optimal transport characteristics were observed for PA/fullerenol (5 wt%) membrane. Novel membranes based on polyphenylene isophthalamide (PA) modified by fullerene derivatives (5 wt% with respect to PA weight) (polyhydroxylated fullerene (fullerenol), carboxyfullerene and fullerene derivative with L-arginine) were developed. The presence of PA/fullerene and PA/fullerene derivative composites and distribution of carbon nanoparticles after ultrasonic treatment in polymer solution was investigated by dynamic light scattering. The influence of carbon modifier on structural characteristics of PA was examined by nuclear magnetic resonance, small-angle X-ray scattering, scanning electron microscopy, atomic force microscopy, sorption experiments, density investigation and contact angle measurements of water. The transport properties were examined by pervaporation separation of industrially important methanol/toluene mixtures in two regimes (1. a series of experiments of different concentrations including azeotropic mixture and 2. only azeotropic mixture) to assess the effect of residual solvent in the PA membranes on their parameters. It was found that all membranes containing fullerene derivatives possessed improved permeation flux compared to pristine PA membrane. The optimal transport characteristics for the separation of methanol/toluene mixtures containing 10–72 wt% methanol were noticed for PA membrane modified by 5 wt% fullerenol due to the highest permeation fluxes (0.084–0.214 kg/(m2h)) and high level of selectivity (95.9 wt% methanol content in the permeate). [ABSTRACT FROM AUTHOR]