Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume
47, Number 6, July 2009, pp. 459-466
The Design by Molecular Dynamics Modeling and
Simulations of Porous Polymer Adsorbent Media Immobilized on
the Throughpore Surfaces of Polymeric Monoliths
E. Riccardi, J.-C. Wang, and A.I. Liapis
Department of Chemical and Biological Engineering, Missouri University
of Science and Technology, 400 West 11th Street, Rolla, Missouri
65409-123
Ion-exchange porous adsorbent media having intermediate
and low surface densities of dextran polymer grafted on the surface
of the throughpores of polymeric monoliths are constructed and
characterized by a molecular dynamics modeling and simulation
approach that has also been shown to be effective in the construction
and characterization of porous ion-exchange adsorbent media whose
number of immobilized dextran polymer chains per unit surface
area is high. The activation step that prepares the surface of
the pores of the dextran polymer layer for the immobilization
of the charged ligands insignificantly affected the pore structure
of the dextran polymer layer, while this was found to not be
the case for previously studied systems that involved high dextran
polymer surface densities. Compared to the high dextran polymer
density system studied previously, the intermediate dextran polymer
density system can generate significantly larger pores but still
possesses relatively high interconnection and mutual steric support
between dextran chains to exhibit similar structural characteristics
and responses to charged ligand immobilization, including dextran
layer thickness, stability, monomer distribution, ligand-induced
compact chain structures, dextran layer shrinkage, distributions
of ligands and counterions, and local nonelectroneutrality. The
low dextran polymer density system having relatively isolated
dextran chains and insufficient mutual steric support can result
in even larger pores than those obtained in the intermediate
dextran polymer density system, but a significantly thinner porous
dextran polymer layer and different dextran monomer distributions
are obtained in the low dextran polymer density system. More
importantly, the gradient of the local nonelectroneutrality after
the immobilization of the charged ligands is significantly smaller
in magnitude in the low dextran polymer density system than that
obtained in the system having intermediate dextran polymer density,
and, despite a lack of porous layer depth to accommodate adsorbate
biomolecules in large amounts, it could still be useful for the
effective transport and adsorption of very large biomolecules.
Compared with the polymeric monoliths without a porous dextran
polymer layer grafted on the surface of their throughpores, the
intermediate and low dextran polymer density systems explored
and studied in this work provide pore structures with desirable
characteristics for the effective transport of adsorbate biomolecules
and substantially larger effective surface areas and throughput
capacities for the adsorption of the adsorbate biomolecules.
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