Adsorption of Polymer Molecules at Low Surface Coverage

Abstract

A statistical-mechanical treatment of a polymer molecule adsorbed on a solid surface is given. The surface coverage by adsorbed molecules is assumed to be sufficiently low that the interactions of the adsorbed polymer molecules with each other may be neglected. The partition function is derived for a polymer molecule with sequences of repeating units adsorbed at an interface and with other sequences (loops) held at the surface only at their ends. The assumption of Gaussian statistics for the loops leads to a formulation equivalent to that used for the helix-coil region in DNA molecules. A broad distribution of loop sizes is found, in contrast to Silberberg's theory in which a sharply peaked distribution is assumed. The latter theory predicts also small loops for all values of the adsorption free energy. In contrast, our theory predicts large loops and few units adsorbed for small adsorption free energies and small loops and more units adsorbed for larger adsorption free energies when the chains are sufficiently flexible. This result is also in partial disagreement with earlier theories that predict large loops, even for relatively large adsorption free energies. On the other hand, for stiff chains our theory predicts only a small number of loops with most units at the surface. A relationship between the initial slope of an adsorption isotherm and the molecular weight of the polymer is presented.

Interfacial Properties of Methylcelluloses: The Influence of Molar Mass

“…It is demonstrated that the interaction is very great for the smaller amounts of added methylcellulose (lower than 5 mg/L). In addition, it is shown that the behavior depends on the molar mass, as is usual for the adsorption of the molecule at the interface forming loops and trains in dependence of the surface free energy [27]. In this model, large loops are formed and a few units adsorbed for small adsorption free energies, but small loops and more units are adsorbed for larger adsorption free energies when the chains are sufficiently flexible.…”

“…Different methods have been proposed to study the adsorption of a polymer at a solid interface [25][26][27][28][29][30][31]. The technique has to be chosen in dependence of the system studied (the nature of the neutral or charged polymer, the bulk concentration of the polymer, the external salt concentration).…”

The behaviour of an ideal polymer chain interacting with two parallel surfaces

“…This last problem turns out to be easy, as all eigenvalues and eigenvectors of W can be found analytically. Then w = mn-' (6) gives W in closed form. Here A is diagonal and L?…”

Polymer concentration profile near a liquid-solid interface: evanescent wave ellipsometry study

“…[9][10][11][12] The galacturonic acid containing matrix polymers exist in a form referred to as pectin or pectinic acid and are based on a backbone rich in a-(1-4)-linked D-galacturonic acid (the homopolygalacturonans) interspersed with (1-2)-and (1-2,4)-substituted 1-rhamnose moieties, which are usually further linked with other neutral sugar polymers, forming "hairy" domains or side chains. The carboxyl groups of some of the galacturonan residues are methyl esterified to various degrees.…”