title: Comprehensive study of the macropore and mesopore size distributions in polymer monoliths using complementary physical characterization techniques and liquid chromatography.
abstract: Poly(styrene-co-divinylbenzene) monolithic stationary phases with two different domain sizes were synthesized by a thermally initiated free-radical copolymerization in capillary columns. The morphology was investigated at the meso- and macroscopic level using complementary physical characterization techniques aiming at better understanding the effect of column structure on separation performance. Varying the porogenic solvent ratio yielded materials with a mode pore size of 200 nm and 1.5 μm, respectively. Subsequently, nano-liquid chromatography experiments were performed on 200 μm id × 200 mm columns using unretained markers, linking structure inhomogeneity to eddy dispersion. Although small-domain-size monoliths feature a relatively narrow macropore-size distribution, their homogeneity is compromised by the presence of a small number of large macropores, which induces a significant eddy-dispersion contribution to band broadening. The small-domain size monolith also has a relatively steep mass-transfer term, compared to a monolith containing larger globules and macropores. Structural inhomogeneity was also studied at the mesoscopic level using gas-adsorption techniques combined with the non-local-density-function-theory. This model allows to accurately determine the mesopore properties in the dry state. The styrene-based monolith with small domain size has a distinctive trimodal mesopore distribution with pores of 5, 15, and 25 nm, whereas the monolith with larger feature sizes only contains mesopores around 5 nm in size.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Brussels, Belgium.
authors.forename: Sam
authors.initials: S
authors.lastname: Wouters
authors.affiliation: Vrije Universiteit Brussel, Department of Materials and Chemistry, Research group of Electrochemical and Surface Engineering, Brussels, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Hauffman
authors.affiliation: University of Amsterdam, Van 't Hoff Institute for Molecular Sciences, Amsterdam, The Netherlands.
authors.forename: Marjo C
authors.initials: MC
authors.lastname: Mittelmeijer-Hazeleger
authors.affiliation: University of Amsterdam, Van 't Hoff Institute for Molecular Sciences, Amsterdam, The Netherlands.
authors.forename: Gadi
authors.initials: G
authors.lastname: Rothenberg
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Brussels, Belgium.
authors.forename: Gert
authors.initials: G
authors.lastname: Desmet
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Brussels, Belgium.
authors.forename: Gino V
authors.initials: GV
authors.lastname: Baron
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Brussels, Belgium.
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Eeltink
keywords: Adsorption isotherms; Column characterization; Gel porosity; Porosimetry; Stationary phases