Polymerization of 5-n-alkyl-substituted 2-norbornenes synthesized a series of polymers having the same structure of the main polymer chain, but differing in the length of the alkyl substituent (up to 14 methylene units). The obtained polymers were studied by the capillary IGC method as a stationary phase during separation of a mixture of normal hydrocarbons C6-C10. Retention data in the form of a logarithm of the retention factor lnk were correlated with the size of the sorbate (via the carbon number of the alkane ZS) and with the size of the n-alkyl substituent in the polymer chain (via the carbon number of the polymer ZP). Correlation of lnk vs. ZS turned out to be linear for all polymers, but the angle of the slope of linear dependence dlnk/dZS increases with a decrease in the carbon number of the polymer ZP. Dependency of dlnk/dZS vs. ZP is not linear and indicates an increase in the retention of sorbates by the stationary phase with a decrease in the length of the alkyl substituent in the polymer chain. The correlation of the retention of lnk analytes with the carbon number of the polymer ZP is not linear and indicates an increase in the sorbate/sorbent interaction with a decrease in the length of the alkyl substituent. Inflection points were found at both correlations with ZP in the region of ZP = 8, which indicates a possible change in the sorption mechanism or a change in the phase state of the polymer. In polymer chemistry, the phase state of a polymer is characterized by the glass transition temperature Tg, the dependence of which vs. ZP turned out to be nonlinear with an inflection point at ZP ∼11. Thus, a decrease in the length of the alkyl substituent leads to the transition of the polymer from a rubbery state to a glassy one at ZP ∼ 11, which in turn, with a further decrease in the carbon number of the polymer to ZP ∼ 8, causes a change in the sorption mechanism from bulk sorption to surface sorption. The change in the sorption mechanism is accompanied by an increase in the interaction of the sorbate with the stationary phase, which manifests itself both in an increase in the retention time of analytes and in an increase in the enthalpy and entropy of sorption. The reason for this increase can be seen in the formation of a microporous structure in 5-alkyl-substituted polynorbornenes in a glassy state.

Based on the properties of the corrected retention volume and, primarily, its independence from the carrier gas pressure, we concluded that the corrected retention volume cannot be a gas volume. We demonstrated that this parameter is identical to the volume of an ideal fluid required for the elution of a sorbate in an ideal chromatographic system. The corrected retention volume does not obey gas laws; because of this, numerous relationships obtained in gas chromatography without taking into account this property of the corrected retention volume should be revised. We considered publications of various authors in order to illustrate inconsistencies and contradictions that follow from the nonrecognition (or rejection) of this fact.

For the well-known theoretical model of hydrodynamic chromatography, which relates the relative retention of an analyte and the separation efficiency to the characteristic parameter of a system, expressions are proposed that make it possible to find the optimal conditions for analysis. The theoretical model well predicts the relative retention of analytes but greatly overestimates the separation efficiency, especially for high molecular weight polymers. The observed discrepancy is due to the impossibility within one separation to create optimal conditions for all components of the sample and/or the influence of the polydispersity of the studied polymer samples on the separation efficiency.

The possibility is verified of estimating the phase ratio of a chromatographic column chromatographically from the semi-empirical dependence of the retention time of homologs on the number of carbon atoms in their structure. The effect the nature and pressure of the carrier gas has on the phase ratio is considered. It is shown that the average value is 1190 ± 100 for the polar phase and 380 ± 50 for the non-polar phase, regardless of the nature of the carrier gas. An exception is СО2, where phase ratio β drops strongly after adjusting the initial data. At the same time, it is clear that the values of the phase ratio determined chromatographically differ strongly from those claimed by the manufacturers of columns, while system dead time tМ and energy $$\Delta {{G}_{{{\text{C}}{{{\text{H}}}_{{\text{2}}}}}}}$$ of the methylene unit sorption of a homological series can be reliably determined via extrapolation.

Polyimide PIM-1, which forms a porous polymer layer on the walls of a capillary column, exhibits high thermal stability. It is studied as a stationary phase for gas chromatography. A column with the PIM-1 stationary phase displays a drastic difference in efficiency, depending on the molecular size of the analyte: 2500–3000 theoretical plates per meter for methane and ethane and fewer than 1000 plates for larger molecules. This behavior of the column is attributed to the poor accessibility of sorption sites, as is apparent from the high loss of entropy during the sorption of light hydrocarbons and the low diffusion coefficients for these sorbates. The effect the physical aging of PIM-1 has on the separating properties of a column is studied in the accelerated thermal aging mode using the example of separation of a model C1–C4 hydrocarbon mixture. It is shown that upon heating the stationary phase to 200°C, sorbate retention and column efficiency fall monotonously. When the temperature is raised to 300°C, an unexpected increase in the analyte retention is observed, though the column’s efficiency continues to fall with respect to all sorbates except isobutane, for which this parameter increases. The causes of these unexpected effects have yet to be revealed.

Changes in retention factor k of light hydrocarbons on PIM-1 stationary phase with an increase of ageing temperature are tested. Varying the ageing temperature from 50 to 200°C causes a slight decrease in solute retention, which, however, changes to strong increase as soon as the ageing temperature exceeds 200°C. An increase of the solute retention factor k means the proportional increase of the Henry equilibrium constant K, which in turn under constant chromatographic conditions probably points out the thermodynamic changes in the structure of PIM-1 which can be caused either by a chemical decomposition or by a structural rearrangement. Due to high chemical stability of PIM-1, an increase of solute retention with thermal ageing is a consequence of structural rearrangements of polymeric chains, resulting in more adapted adsorption sites. At the same time, accessibility of the adsorption sites decreases as it is indicated by the reduction of column efficiency and diffusion coefficients.

The article discusses two major problems in teaching physics for students majoring in IT at a technical university: 1) the forced change in the course structure and content due to the reduction in the time allotted for studying physics from three to two semesters, and 2) the uneven educational background of applicants, due to the fact that when entering a university, the results of the Unified State Examination in physics are not taken into account. The article analyzes the experience of the Physics Training Center at the ITMO University in St. Petersburg on conducting additional consultations on the school curriculum materials and on the development and using of electronic educational materials. The relevance of courses that are concentric in their structure, created by colleagues from the other universities, is noted. The authors propose to organize training for first-year students in various educational tracks, depending on their starting level. The article emphasizes the importance of maintaining completeness and ideological value of the course when revising the structure and content. The following conceptual scheme of the course is proposed: elementary physics as axiomatic science, statistical physics, quantum physics, quantum field theory (general concepts). The experience of the development and using of electronic educational materials (lecture presentations, electronic summaries of lectures and exercises) at ITMO University is analyzed. Despite the fact that, in general, e-learning elements make it possible to compensate the lack of class time caused by the program changes, students learn e-courses at different levels. It is noted that the reason, apparently, lies in the psychological unreadiness of a number of students to switch to “blended learning”. It is emphasized that in the mixed course creation the development of materials for assessing student performance and their final certification is a fundamentally new and time-consuming task, the preference is given to the traditional full-time exam. The authors consider that it expedient to preserve the traditional structure of the physics course at technical university.

Different ways of estimating the hold-up time of a system in gas chromatography are considered. It is shown that the hold-up time found from aerodynamic dependences proves to be minimal, but does not allow for the contribution from extracolumnar effects. The hold-up time, determined experimentally from the retention time of an unretainable sorbate (methane), proves to be maximal and depends on the intensity of sorbate–stationary phase interaction. The hold-up time found from the purely empiric correlation between the logarithm of the net retention time of homologs and the number of carbon atoms is intermediate between the theoretical and experimental values. It is shown that the correlation between the number of carbon atoms in a homological series and the relative retention time of sorbates (rather than their net retention time) is grounded thermodynamically. Corresponding correlations are proposed that allow estimates not only of the hold-up time of a system but also of such parameters as the phase ratio and the change in the free energy of a methylene unit during sorption on the stationary phase.

The thermodynamic parameters of sorption of a test mixture of hydrocarbons on a new type of PEG-like stationary phases are determined from the temperature dependence of sorbate retention in the temperature range of 35–110°C. The determined entropy and enthalpy of sorption are close for all the studied stationary phases, despite the different ratios of ethylene glycol and acrylate moieties in the polymer’s phase structure. At the same time, the studied phases exhibit greatly different separation abilities, due apparently to the kinetic properties of the phases, as is indicated by differences in the efficiency of the columns with these phases and in the diffusion coefficients of sorbates on these phases.

It is shown that the model of interaction of high-power few-cycle optical pulses with media, which is based on the density matrix formalism, is capable of simultaneously considering generation of longwave radiation in the infrared and terahertz range and describing the broadening of the radiation spectrum into the high-frequency region. The results of the mathematical modeling are compared to the known experimental data.

Термодинамические параметры сорбции тестовой смеси углеводородов на новом типе ПЭГ-подобных стационарных фаз определены из температурной зависимости удерживания сорбатов в диапазоне температур от 35 до 110?°С. Найденные величины энтропии и энтальпии сорбции оказались близкими для всех стационарных фаз, изученных в этой работе, несмотря на различное соотношение этиленгликольных и акрилатных фрагментов в структуре полимерной фазы. В то же время изученные фазы заметно отличаются по их разделяющей способности, что, вероятно, связано с кинетическими свойствами фаз, на что указывают различия в эффективности колонок с этими фазами и в коэффициентах диффузии сорбатов на этих фазах.

A mixture of polystyrene standards with molecular weights ranging from tens of thousands to tens of millions of Da is separated on capillary columns with diameters of 2 and 5 μm. The correspondence between the experimental time of GDC elution to a universal calibration curve is investigated. It is shown that acceptable values of the C parameter of the calibration curve can be obtained only with calibration in universal coordinates. The concepts of critical molecular weight and critical elution time in GDC are introduced, and it is noted that despite the high molecular weights of the polymers that are used, their behavior is still very far from the critical point. This hinders reliable experimental determination of the C parameter. A strong drop in column efficiency in the separation of high molecular weight polymers against a backdrop of simultaneous high-efficient separation of oligomeric polymers is observed.