Influence of the Chain Architecture and the Presence of End-Groups or Branching Units Chemically Different from Repeating Structural Units on the Critical Adsorption Point in Liquid Chromatography

Abstract

The critical adsorption point (CAP) of linear and star-shaped polymers was investigated by normal phase and reversed phase liquid chromatography (NPLC and RPLC) and computer simulation. Three sets of polystyrenes (PS) differing in chain architecture and chemically distinct groups were prepared: linear PS (sec-butyl and hydrogen end group), 2-arm PS (linear, two sec-butyl end groups and one silyl group in the middle of the chain) and 4-arm star-shaped PS (four sec-butyl end groups and one silyl group in the center of the star). It was found that the column temperature at CAP, T CAP (linear PS) = T CAP (2-arm PS) > T CAP (4-arm PS) in both RPLC and NPLC which can be attributed to the variation in chain architecture. However, the elution times at CAP of three polymers are all different: In NPLC, t E,CAP (linear) > t E,CAP (2-arm PS) > t E,CAP (4-arm PS) while in RPLC, t E,CAP (4-arm PS) > t E,CAP (2-arm PS) > t E,CAP (linear). The variation of t E,CAP can be explained by the contribution of the chemically distinct groups. The computer simulation results are in good agreement with the chromatography experiments results and support the interpretation of experimental data.

Column Characterization and Selection Systems in Reversed-Phase High-Performance Liquid Chromatography

“…Most of the recent molecular simulation studies employed MD to examine the retention process in RP-HPLC. ,− These calculations yield a microscopic picture of the local structure and dynamics of the RP-HPLC interface on an atomic scale. In a typical model of a chromatography system, a periodic boundary condition with a particular unit cell dimension (e.g., 40 × 40 × 80 Å) is applied to generate a mimic of each molecular model, which consists of four parts: silica support, ligands (i.e., alkyl chains) with a particular surface coverage, solvent molecules (e.g., water/methanol mixture), and solutes.…”

Separation of Branched Poly(bisphenol A carbonate) Structures by Solvent Gradient at Near-Critical Conditions and Two-Dimensional Liquid Chromatography

“…In addition to the findings and explanations of Ahn et al, also the influence of additional end-groups in the branched chains might be considered. Radke et al and Biela et al demonstrated the influence of the local distribution of functional (end-)­groups along the polymer chain on the elution behavior in LCCC.…”

“…The exceptional elution behavior might be explained by a combination of the influence of architecture and end-groups of the branched polymer chains. Ahn et al 50 observed a SEC elution for 4-arm star-shaped PS at the critical conditions of linear PS in NPLC. Interestingly, the same 4-arm star-shaped PS eluted in "pseudo-SEC" mode at the critical conditions of linear PS in RPLC; however, the 4-arm star-shaped PS eluted at volumes, which would be indicative for LAC elution.…”

DPD Modelling of the Self- and Co-Assembly of Polymers and Polyelectrolytes in Aqueous Media: Impact on Polymer Science

“…They enable checking of the correctness of theoretical hypotheses and predictions and provide data that are either inaccessible or barely accessible by experiments. Furthermore, in combined experimental and theoretical research, they offer a relatively fast and cheap substitute for a substantial part of the tedious and expensive experimental work [90][91][92][93][94]. Thanks to enormous progress in computer technology, atomistic simulations (even quantum simulations) of relatively large systems, such as enzymes and catalytic or biocatalytic centres, have become feasible in recent decades [95][96][97][98][99].…”