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In this work, the Coulson‐Longuet‐Higgins response function (atom‐atomic polarizabilities [AAPs]) is used to describe the transfer of an electron perturbation in π‐conjugated systems in the presence of a static electric field. Computations are performed using different many‐electron approaches to study the effect. An accurate account of the electron correlation is shown to play a key role in the description of the interaction of a π‐shell with the external electrostatic field. Studies in this work reveal that the Hückel theory widely used in calculations of electron‐perturbation transfer is not reliable even at the qualitative level to describe the effects studies in this work. However, the π‐electron coupled cluster theory has been proven capable of providing a reliable electronic structure (among them, AAPs and excitation energies) that agree with the results obtained with the π‐electron full configuration‐interaction approach. The calculations also show that these properties have an essentially nonlinear character in terms of the strength of the applied electric field. The results obtained in the present work can provide useful information relevant to the application of π‐conjugated systems in molecular electronics. [ABSTRACT FROM AUTHOR]

Atom force microscopy was used to study the supermolecular structures of polycarbonate-based composites. The effect of modifiers on the formed supermolecular structures was investigated, and the dependence of the properties of the composites on their structure was established. [ABSTRACT FROM AUTHOR]

In the present work, an assessment is made of the use of single-layer carbon nanotubes as a replacement for traditional pigments for the coloration and modification of polymers on an industrial scale, and the physicomechanical, thermodynamic, and colour characteristics of specimens coloured with different pigments are analysed in detail. [ABSTRACT FROM AUTHOR]

A new semi-empirical π-electron local coupled cluster theory has been developed to calculate static dipole polarisabilities and hyperpolarisabilities of extended π-conjugated systems. The key idea of the approach is the use of the ethylene molecular orbitals as the orbital basis set for π-conjugated compounds (the method is termed the Covalent Unbonded Molecules of Ethylene method,cue). Test calculations of some small model organic conjugated compounds demonstrate high accuracy of the version of thecuelocal coupled cluster theory developed in this work in comparison with the π-electron full configuration interaction (FCI) method. Calculations of different conjugated carbon-based oligomer chains (polyenes, polyynes, polyacenes, polybenzocyclobutadiene, etc.) demonstrate fast convergence (per π-electron) of the polarisability and hyperpolarisability values in the calculations when more classes of orbital excitations are included in the coupled cluster single and double (CCSD) excitation operator. The results show qualitatively correct dependence on the system size. [ABSTRACT FROM AUTHOR]

Capabilities of line (edge) graph in quantitative structure‐activity relationship (QSAR) problem for constructing predictive models are demonstrated. The basic idea for proposed approach is to describe molecular structure using generated graph sequence: vertex and chain of line graphs. Every following graph in the sequence corresponds to the structure where vertices appear to be edges of the previous one. For every graph, it is proposed to compute corresponding topological and informational descriptors. Employing latter for derivation of predictive equations allows to realize progressive hierarchy of models. As a test problem, the forecast of research octane numbers for saturated hydrocarbons is chosen. Among the descriptors selected to be used for building regression models well‐known Randic connectivity index (χ(1)), first Zagreb index (ZM1) and theoretic‐informational index of vertex complexity (Vc) are employed. Derived hierarchy of regression equations shows systematic improvement in the description of desired property as every new graph is included in consideration. Determination coefficients for training sample and computed via leave‐one‐out cross‐validation procedure reveal that four‐parametric equation with Vc descriptor has satisfactory forecasting facilities. Efficiency of proposed approach was also demonstrated on the example of artificial neural networks. Capabilities of line graph in QSAR problem for constructing prognostic models are demonstrated. The basic idea is to describe molecular structure using graph sequence: vertex and chain of line graphs. For every graph, it is proposed to compute corresponding topological and informational descriptors. Employing latter for derivation of predictive equations allows to realize progressive models hierarchy. Proposed approach efficiency was demonstrated on artificial neural networks example. Methodology is called to simplify the descriptors' selection procedure in application to neural networks. [ABSTRACT FROM AUTHOR]