Interactions of complex polymers with nanoporous substrate

Abstract

With the advance of polymer synthesis, polymers that possess unique architectures such as stars or cyclic chains, and unique chemical composition distributions such as block copolymers or statistical copolymers have become frequently encountered. Characterization of these complex polymer systems drives the development of interactive chromatography where the adsorption of polymers on the porous substrate in chromatography columns is finely tuned. Liquid Chromatography at the Critical Condition (LCCC) in particular makes use of the existence of the Critical Adsorption Point (CAP) of polymers on solid surfaces and has been successfully applied to characterization of complex polymer systems. Interpretation and understanding of chromatography behaviour of complex polymers in interactive chromatography motivates theoretical/computational studies on the CAP of polymers and partitioning of these complex polymers near the CAP. This review article covers the theoretical questions encountered in chromatographic studies of complex polymers.

Critical Depletion, Adsorption, and Intersurface Interaction in Polymer Solutions: A Mean-Field Theory Study

“…Thermodynamics and interfacial properties of polymer solutions near surfaces play a fundamental role in various applications such as surface coating, polymer chromatography, and stabilization of colloidal suspensions. − For example, adding a small amount of nonadsorbing polymers into a colloidal suspension can lead to flocculation due to the entropic depletion attraction, , but the addition of adsorbing polymers may lead to the formation of an irreversible surface layer, ,, which enhances the stability through steric repulsion among these layers. , Owing to the efforts taken in the last several decades, the effect of polymers on the interaction between colloidal particles has been well-understood in both good and Θ solvents. ,,, On the other hand, in the critical regime, bulk polymer solution exhibits quite distinct features from those in the off-critical regime , due to the long-range concentration fluctuations. It is thus rather natural to expect that the surface properties of polymer solutions should be also quite different in the critical regime.…”

“…In parallel to the above confined polymer solutions, when a polymer solution is exposed to a single hard surface (termed “single-surface system” hereafter), chains will be depleted from the surface when the surface–polymer interaction is weak, and a depletion–adsorption transition (DAT) takes place when the surface–polymer attraction becomes sufficiently strong. − This DAT is highly relevant to the liquid chromatography at the critical condition. ,− For the single-chain adsorption that is valid when the bulk solution is sufficiently dilute, the DAT is a smooth crossover for finite chain length N and becomes a true second-order phase transition when N → ∞. , For the multichain adsorption, it is generally believed that this transition is a smooth transition for finite N . However, all these studies focused on the good or Θ solvent conditions, and an investigation on how this transition changes and how the surface tension is affected when the bulk solution approaches its critical point is still lacking.…”

Comparison of Critical Adsorption Points of Ring Polymers with Linear Polymers

“…Experimental determination of the CAP is nearly impossible except in the field of liquid chromatography. In the past two decades, polymer liquid chromatography has developed the so-called liquid chromatography at the critical condition (LCCC) where homopolymers with different molecular weights (MW) coelute at the LCCC. − Ample evidence suggests that this LCCC condition coincides with or is closely related to the CAP. ,− Experimentalists typically achieve this LCCC condition by changing the eluent composition and/or the column temperature to achieve a point where polymers with different MW coelute. Comparison of LCCC conditions found for different types of polymers usually will not yield useful information since the LCCC condition depends on the chemical nature of polymer repeating units, chromatography columns, and solvents.…”

Modeling the Phase Equilibria of Associating Polymers in Porous Media with Respect to Chromatographic Applications

“…The computer simulation is an intelligent, powerful, and extraordinarily suitable approach for the investigation of the above-listed interrelated processes. Although the bulk-pore (also called the twin-box) model has been well developed and extensively employed in simulations of the partitioning of various polymers [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ], to the best of our knowledge, the computer-aided interpretation of LC data on the partitioning of associating polymers has not yet been published. In this work, we study the bulk association of block copolymers in a selective solvent, and their partitioning and adsorption on porous media.…”