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

Abstract

Using a self-consistent field theory, we examine the thermodynamics and interfacial properties of a homopolymer solution, either close to a single hard surface or confined between two parallel surfaces, in equilibrium with a bulk reservoir. We focus on the bulk critical regime and find that various physical quantities therein exhibit qualitatively different behaviors from those in the off-critical regime. For the single-surface system, the surface-excess Γ diverges as ln|ϕb – ϕc| and ln|χc – χ| when approaching the bulk critical point, where χ and ϕb are the Flory–Huggins interaction parameter and the volume fraction of polymer segment in bulk solution, respectively, and χc and ϕc are their respective values at the critical point. Γ diverges to +∞ when the surface–polymer interaction εs is larger than the depletion–adsorption transition (DAT) point εc, and to −∞ when εs < εc. As such, the DAT at εc in the critical regime is rather sharp and εc = 0.1824 + 0.1359N –1/2 at large N. For the two-surface system, the intersurface potential W at the critical point is purely attractive for both depleted and adsorbed cases and follows a D –3 power-law decay at large intersurface separations D; when εs is close to εc, the strength of W becomes rather weak. This nonmonotonic dependence of W on εs has important experimental implications on the stability of colloidal suspensions.

Tuning of scleroglucan adsorption on carbonate surfaces via grafting alkyl side chains of different lengths: a theoretical and experimental study

“…Actually, an increase in the solution temperature decreases the polymer/ solvent FH interaction parameter (w mc/solvent = 1.02, at 25 1C and w mc/solvent = 0.76, at 90 1C) by improving the solvent quality. Zhang 29 has shown that for a flexible polymer adsorption from its different solutions on various surfaces, the effect of polymer/ solvent w value on the surface excess of the polymer depends on the polymer/surface interaction parameter. According to Zhang, below a critical polymer/surface interaction parameter (w c ), the surface excess is increased with decreasing the polymer/solvent FH interaction parameter, i.e., by increasing the medium temperature for systems with an UCST behavior.…”

“…According to Zhang, below a critical polymer/surface interaction parameter (w c ), the surface excess is increased with decreasing the polymer/solvent FH interaction parameter, i.e., by increasing the medium temperature for systems with an UCST behavior. The w c is related to the number of repeat units of the main chain (r mc ) by eqn (35): 29 w c = 0.1359r mc À1/2 + 0.1824 (35) Considering M w = 8 Â 10 5 g mol À1 as the molecular weight of the Sclg main chain of the modified samples, the r mc and w c values for the hydrophobically modified Sclgs are calculated as 5000 and 0.18, respectively. The FH interaction parameters of alkyl side chains and the carbonate surface (w sc/ss = 0.14, at 2) are smaller than the calculated w c = 0.18, by eqn (35).…”

“…Besides the structural and architectural parameters of polymer chains, the operational factors such as temperature, salinity, pH, and particularly the solvent quality (solvent–polymer interaction parameter, χ ) also affect the surface excess amount and arrangements of adsorbed chains on surfaces. For example, by using a SCFT approach, Zhang 29 showed that at a certain surface–polymer interaction, the solvent quality significantly affects the polymer surface excess.…”

Comparison of Linear and Ring Polymers Partitioning into Pores Using Random Walks and Self‐Avoiding Walks Models

“…It might also depend on the concentration of the polymer solution, which will not be discussed here. [34] Because of this chain-length dependence, the CAP is normally defined in theory by extrapolating to the infinite chain length. [35][36][37][38] One question that remains to be answered then is whether the CAP for the ring polymer and linear polymer remains the same at the infinite chain length limit.…”

Selective Adsorption of Confined Polymers: Self-Consistent Field Theory Studies

“…Previous theories mainly focus on the adsorption of homopolymer corresponding to the nonselective adsorption. The conventional polymer adsorption problem can be in broad terms rationalized as the tug of war between the attractive interaction of the polymer to the surface and the conformational entropy loss of the polymer as it is being adsorbed to the interface. ,− As one of the typical examples of nonselective adsorption, the adsorption of homogeneous polyelectrolytes by oppositely charged surfaces has been widely studied, − including the effects of solution salinity, charge density, length and stiffness of polyelectrolytes, and curvature and charge distribution of surfaces.…”