Stationary Phase Based on Hypercrosslinked Polystyrene for Capillary Gas Chromatography
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ICAL CHEMISTRY OF SEPARATION PROCESSES. CHROMATOGRAPHY
Stationary Phase Based on Hypercrosslinked Polystyrene for Capillary Gas Chromatography V. E. Shiryaevaа, T. P. Popovaа, A. A. Korolevа, A. Yu. Kanat’evaа, and A. A. Kurganovа,* а
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia *e-mail: [email protected] Received November 19, 2019; revised January 20, 2020; accepted February 11, 2020
Abstract—A capillary column for gas chromatography was prepared using microspherical particles of hypercrosslinked polystyrene. The hypercrosslinked stationary phase approximates the stationary phases based on the poly(trimethylsilylpropyne) membrane polymer according to the sorption enthalpy of light hydrocarbons, but proved markedly inferior to the latter phases according to the kinetic efficiency. Direct synthesis in a column with a hypercrosslinked stationary phase based on hypercrosslinked polystyrene led to the formation of a nonporous polymer, which had no separating ability with respect to light hydrocarbons. Keywords: gas chromatography, stationary phases, polymers, sorption thermodynamics, sorption kinetics DOI: 10.1134/S0036024420090253
INTRODUCTION The diversity of stationary phases used in modern gas chromatography (GC) can be divided into two large groups: porous and nonporous stationary phases. The latter are often referred to as “liquid” stationary phases, as their first representatives were, in fact, highboiling organic liquids. Currently, the majority of stationary phases from both the first and second groups are synthetic high-molecular compounds [1]. The porous polymer stationary phases can also be divided into two large groups: classical macroporous polymers and polymers with internal porosity. Conventional macroporous polymers are obtained by polymerization of monomers in the presence of special additives—porogens, whose amount and structure determine the porous structure of the resulting polymer [2]. To stabilize the porous structure of macroporous polymers, the polymer chains are crosslinked in a definite way, fixing their spatial position. In contrast, polymers with internal porosity do not contain any cross-links, and their porosity appears because of the inability of polymer chains to be densely packed in a solid polymer for steric reasons [3]. These polymers have a microporous structure and increased void volume. From the thermodynamic viewpoint, however, this structure of the polymer matrix is not equilibrium and slowly changes with time into a structure with a denser packing of polymer chains, which is naturally accompanied by a decrease in the void volume (the so-called physical aging of polymers) [4]. The cross-linked polymer structures are more stable over time, but it was problematic to obtain cross-
linked microporous structures with a highly developed inner surface and acceptable pore volume. This problem was solved when methods for the preparation of so-called hypercrosslinked polymers were developed [5], which are obtained by cross-linking the poly
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