Unusual Structural Changes of PIM-1 Polymer Detected by Means of Chromatographic Technique
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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.
This work was carried out within the State Program of A.V. Topchiev Institute of Petrochemical Synthesis of Russian Academy of Sciences (TIPS RAS).
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