Chain segment concentration surfaces

Fig. 2.15 Relative ideal chain segment concentrations at a wall and at a sphere fen-q = 0.1, = 1, and 9 = 10 accOTding to (2.59). With increasing q the profile shifts closer to the surface...

Part (a) is the driving force for the adsorption. If only (a) were present, adsorbed chains would lie flat on the surface. Parts (b) and (c) are the opposing forces (b) accounts for the entropy loss of a bond on the surface as compared to the solution, (c) represents the separation into a concentrated surface phase and a dilute solution. Part (d) arises from polymer-polymer, solvent-solvent and polymer-solvent interactions, which usually favour accumulation of segments. At equili-... 

When the polyelectrolyte chains form bridges between two plates, the plates are pulled towards each other by the chains. If the van der Waals interactions between the segments of the chains and the surfaces are sufficiently strong, the increased polymer concentration in the gap between the plates can significantly affect the bridging force between them. 

Rejection of protein adsorption to the outermost grafted surface is attributed to a steric hinderance due to the tethered chains. A grafted surface in contact with an aqueous medium, a good solvent of the chains, has been identified to have a diffuse structure [67]. Reversible deformation of tethered chains due to invasion of mobile protein molecules into the layer would lead to a repulsive force which is governed by the balance of entropic elasticity of the chains and osmotic pressure owing to the rise in the segment concentration. The overlapped repulsive force would prevent the direct contact of protein molecules with the substrate surface. 

Figure S.6. Schematic representation of a poljrmer concentration profile as a function of distance 2 from the interface. The upper curve gives the overall segment concentration c(z), the lower curve the concentration c (z) due to non-adsorbed chains. Both curves approach the bulk solution concentration c at large 2. The hatched area is the polymer surface excess r , the sum of the shaded and hatched areas represents the total...

For situations of overlapping chains, where lateral fluctuations in the segment concentration become rather small, mean-field descriptions become appropriate. The most successful of this type of theoiy is the lattice model of Scheutjens and Fleer (SF-theoiy). In chapter II.5 some aspects of this model were discussed. This theory predicts how the adsorbed amount and the concentration profile 0(z) depend on the interaction parameters and x and on the chain length N. From the statistical-thermodynamic treatment the Helmholtz energy and, hence, the surface pressure ti can also be obtcdned. When n is expressed as a function of the profile 0(z), the result may be written as ... 

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