How well can one separate copolymers according to both chemical compositions and sequence distributions?


Partitioning of statistical AB type copolymer chains into a slit pore was studied with Monte Carlo simulations on a simple cubic lattice with self-avoiding walk models. Only one of the monomer types, B monomers, has attractive interaction with the surface, while the A monomers have no interaction with the surface. The critical adsorption point (CAP) of the copolymer at a given chemical composition fB and sequence order parameter λ, which characterizes the degree of blockiness in the copolymer, was determined. The CAP's obtained in the simulations were compared with theoretical predictions proposed by Brun [J. Liq. Chromatogr. Relat. Technol. 1999, 22, 3027-3065]. Most simulation data agree well with Brun's theoretical equation except for sequences at the two extreme of sequence types (i.e., extremely blocky or nearly perfectly alternating). The potential separation of copolymers according to chemical composition in interactive chromatography was examined by examining the partition of copolymers at chosen surface interaction energies. Simulation results show that one can separate the copolymers according to the chemical composition only when the sequence order parameter λ is fixed or has a narrow distribution. The separation will be impaired if there is also a distribution in λ. Separation of copolymer samples according to sequence order parameter at a given chemical position is of limited resolution. © 2010 American Chemical Society.

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