In order to relate the microstructure of polymer chains to the gas permeation properties, a novel method is proposed for the calculation of the van der Waals (Vw), occupied (Vocc), and accessible (Vacc) volumes of polymers, using polyimides as examples. In this approach, Vocc and Vacc values are obtained as characteristics of polymer–gas systems. Correlations between Vocc and the gas permeability (P) and diffusion (D) coefficients are demonstrated. Accessible volume, Vacc, determined experimental densities, and Vocc calculated using a Monte Carlo technique, as well as the fractional accessible volume (FAV) (Vacc/Vsp), where Vsp is the specific volume of polymers, also correlate well with the P and D values. The slopes of these correlations increase with increasing molecular size of the diffusing molecules. In addition, the parameters of the equations for D(FAV) and P(FAV) strongly depend on conformation rigidity (Kuhn segment) of the polyimides. An interpretation of the results obtained is presented.Definition of occupied volume.imageDefinition of occupied volume.

Conformational parameters for a wide variety of aromatic cyclochain polymers have been computed assuming free rotation about virtual bonds. The flexibility with free rotation is shown to be determined by the geometry of the repeat unit and can vary over a wide range (15–1500 Å). Experimental values of the Kuhn segment length A are calculated from literature data on the hydrodynamic behavior of polymeric macromolecules of this class in solution. For most polymers Afr for free rotation is equal to the experimental Aexp, and hindered rotation is mainly due to bulky substituents. © 1993 John Wiley & Sons, Inc.

The phenomenological dependences of several physical properties such as the softening temperature, friction coefficient, elasticity modulus, fire-resistance parameters and quantum luminescence yield on the conformational rigidity of a polymeric chain are revealed for polyheteroarylenes. The contribution of the conformational rigidity of a polymer chain to the physical properties of this class of polymers is shown to be significant. It should be taken into account in estimation of the above-mentioned properties together with the contribution of intermolecular interactions.

Complexes of polyelectrolyte gels with oppositely charged surfactants form ordered polymer matrices with unique structure properties, which can be used in a wide range of medical, chemical and physical applications. Ordered matrices made of natural components are of special interest for medical and biological purposes. In the present study, self‐organised complexes of native ι‐ and κ‐carrageenans formed with oppositely charged cetylpyridinium chloride (CPC) are prepared and structurally characterised using small‐angle X‐ray scattering (SAXS). Starting from the molar ratio CPC/(charge of carrrageenan) of 0.2, the carrageenan gel shrinks and ordered motifs in its internal structure are formed. The internal order in the sample is reflected by the Bragg peaks in the scattering patterns which permit to compute periodicity and characteristic sizes of the ordered regions. Moreover, strong central scattering appears and the calculated fractal dimensions indicate that these regions are organised in well defined clusters. The periodicity of the ordered motifs computed from the Bragg peaks in the scattering patterns corresponds to the width of the surfactant bilayer (about 4.0 nm) for all the complexes. The crystallite size ranges from 25 nm to 40 nm depending on the type of carrageenan and on the amount of CPC. A model of the ordered fragments is proposed whereby the carrageenan/surfactant bilayers are regularly packed at the walls of hollow cylindric clusters with the outer radius of about 8 nm and height 40 nm. More detailed ab initio models indicate that these particles are formed by bent worm‐like substructures with the cross‐section coinciding to the thickness of the carrageenan/CPC bilayer. Thanks to a higher charge density per monomer, ι‐carrageenans form more regular structures than κ‐carrageenans.

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