Chemical Sciences and Advanced Chromatography 2019: Separation of parent homopolymers from diblock copolymers by liquid chromatography under limiting conditions of desorption. Block copolymers with highly adsorptive blocks - Dusan Berek - Polymer Institute of the Slovak Academy of Science

Author(s): Dusan Berek

Abstract

Synthetic block copolymers represent an important group of advanced materials with numerous specific applications. Polymer chains with different chemical or physical characteristics are bonded together in the block copolymers to obtain required properties. Most block copolymers however, contain free, non-attached chains, their parent homopolymers, which form expensive ballast. The separation and molecular characterization of parent homopolymers from the block copolymers is an analytical challenge. The selectivity of exclusion based gel permeation chromatography, which is commonly applied for separation of macromolecules according to their size, usually does not enable separation of parent homopolymers from the block copolymers. Coupled liquid chromatography methods, CLC that combine exclusion with interaction separation mechanisms may solve the problem. A novel, high selectivity CLC approach is liquid chromatography under limiting conditions of desorption, LC LCD. LC LCD column is packed with polar, porous, adsorptive material. Eluent suppresses sample adsorption. The multicomponent polymers are separated due to the action of a zone of appropriate liquid barrier injected into a column before sample solution. The molecules of the barrier permeate the packing pores and elute slowly, while the pore-excluded macromolecules tend to proceed fast. The barrier promotes adsorption of interactive polymer chains within the column and decelerates their elution. Then non-interactive chains elute freely. As result, macromolecules with distinct polarities are efficiently separated based on the difference in their adsorptivity. Numerous parent homopolymers were separated from their block copolymers with help of LC LCD. However, high polarity polymer chains such as poly (4-vinyl pyridine) and poly(N-vinyl pyrrolidone) are fully retained within common bare silica gel column packing’s even using the strongest desorbing eluents available. To solve the problem, various less polar adsorptive column packing’s were tested. We will show that silica gel with bonded poly(ethylene oxide) chains enables to efficiently separate above parent homopolymers from their block copolymers.

Recent Publications

1. Berek D (2017) Separation of parent homopolymers from nonpolar block copolymers by means of liquid chromatography under limiting conditions of enthalpic interactions. Macromolecular Chemistry Physics 218:137-142.
2. Berek D (2016) Critical assessment of “critical” liquid chromatography of block copolymers (2016) Journal of Separation Science 39(1):93–101.
3. Berek Dand Macova E (2015) Liquid chromatography under limiting conditions of desorption 6: Separation of a four-component polymer blend. Journal of Separation Science 38(4):543-549.
4. Rollet M, Pelletier B, Altounian A, Berek D and Maria S (2014) Separation of Parent Homopolymers from Polystyrene-b-poly(ethylene oxide)-b-polystyrene Triblock Copolymers by Means of Liquid Chromatography: 1. Comparison of Different Methods, Analytical Chemistry 86:2694−2702.
5. Siskova A, Macova E and Berek D (2012) Liquid chromatography under limiting conditions of desorption 4: Separation of blends containing low-solubility polymers. European Polymer Journal 48(1):155-168.

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