Pharmaceutica Analytica Acta

Advanced liquid chromatography methods for comprehensive molecular characterization of synthetic polymers

International Conference and Exhibition on Advances in HPLC & Chromatography Techniques

March 14-15, 2016 London, UK

Dusan Berek

Slovak Academy of Sciences, Slovakia

Scientific Tracks Abstracts: Pharm Anal Acta

Abstract:

Most high-performace synthetic polymers exhibit besides dispersity in their molar mass also dispersity in another molecular characteristic, namely in chemical structure (composition) or in physical architecture of macromolecules. They are designated complex polymers. Typical examples of complex polymers are all kinds of copolymers, branched and functional polymers. Blends of macromolecules with distinct chemical structure or physical architecture are called complex polymer systems. Size exclusion chromatography (gel permeation chromatography), SEC/GPC is commonly used for assessment of molar mass averages and dispersities (distributions) of complex polymers and complex polymer systems. However, due to simultaneous dependence of size of macromolecules on all their molecular characteristics, as well as following limited separation selectivity, sample capacity, and low detector sensitivity, SEC/GPC can hardly give quantitative information on molar masses of complex polymers and complex polymer systems. For example, SEC/GPC even does not enable molecular characterization of binary polymer blends of components with fairly different molar masses, in which the content of the minor constituent is less than few percent. To characterize complex polymers and complex polymer systems, enthalpic retention mechanisms are to be coupled with entropy based size-exclusion retention mechanism. Of the presently utilized coupled methods of polymer LC the best known are liquid chromatography under critical conditions of enthalpic interactions, LC CC, eluent gradient liquid chromatography, EG LC and temperature gradient interaction chromatography, TGIC. The common drawbacks of the latter methods are limited to both sample recovery and capacity. LC CC permits only separation of two distinct sample constituents. Recently an alternative group of coupled LC metods was developed, namely liquid chromatography under limiting conditions of enthalpic interactions, LC LC. Similar to LC CC and EG LC, the molar mass effect is supressed also in LC LC. LC LC exhibits remarkable separation selectivity, as well as both high sample capacity and recovery. Moreover LC LC is highly robust, experimentally feasible and well repeatable. It was successfully applied to separation of chemically and physically similar macromolecules including low solubility polymers. The method enables reliable identification of very low (<1% and even <<1%) amounts of minor macromolecular admixtures in a polymer matrix. The basic principle of LC LC will be discussed in the contribution. For a comprehensive molecular characterization of complex polymer systems, two different retention mechanisms are to be applied in two separate chromatographic systems. This is the basis of two-dimensional polymer liquid chromatography, 2D-LC. A flexible approach called sequential two-dimensional polymer liquid chromatography, S2DLC was recently developed. It consists of a combination of LC LC and SEC/GPC. The fractions produced by the LC LC column are in their entirety transferred into the SEC/GPC column for determination of average and disperity of sample. The principle of S2D-LC will be elucidated in detail and the typical examples of its application will be shown, especially separation and characterization of block copolymers that contain (small) amounts of their parent homopolymers.

Biography :

Dusan Berek graduated with an honor in Master of Chemical Engineering from the Slovak Technical University in Bratislava. He did his PhD thesis at Polymer Institute, Slovak Academy of Sciences in Bratislava and Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences in Prague. He was employed at Polymer Institute, Slovak Academy of Sciences (PI SAS) in Bratislava since 1960. He was an elected member of the Presidium of the Slovak Academy of Sciences from 1992-1995. He served as President of the Slovak Chemical Society, Chairman of the Czecho-Slovak and Slovak National Committee of Chemistry for the International Union of Pure and Applied Chemistry and as Member of the Board of the Federation of European Chemical Societies. He is the author or co-author of two monographs on liquid chromatography and 250+ scientific papers in extenso published in refereed periodicals (150+ in the Current Contents covered Journals), and in proceedings and chapters of books, as well as 60+ patents (four of them were licensed) - cited more than 2,000 times in SCI journals and monographs.

Email: dusan.berek@savba.sk