Adsorption of the polypeptides on a solid surface. III. Behavior of stiff chains in a pore

A strict analytical theory has been developed describing the behavior of a model lattice polymer chain of arbitrary stiffness in a slitlike pore at polymer–adsorbent interaction energies –ε. The thermodynamic characteristics of the system were calculated. It was shown that the transition of the macromolecule from the solution volume inside a pore occurs by the first‐order phase transition with evolution of latent heat of adsorption. The transition point –ε = –ε c is determined by the chain stiffness and is independent of the pore width D . It is shown that in the precritical range, –ε < –ε c , the free energy Δ F of the macromolecules in the pores is adequately described by the universal dependence Δ F = Δ F ( D */ A ), where D * is some effective pore width depending on the value of –ε, and A is the length of the Kuhn segment. At high attraction energies, –ε ≫ –ε c , the macromolecules are bonded to the pore walls by a great number of units and their free energy depends only on –ε and the chain stiffness, Δ F = Δ F ( A , ε). Close to the critical energy –ε ≃ –ε c (transition range), Δ F is determined by both the stiffness of the macromolecule and the pore width D : Δ F ∼ A 2 D −1 for fairly high values of A and D . The possibilities of using porous media as protein stabilizers are discussed, and the value of the stabilizing effect depending on the chain stiffness is estimated.