Adsorption of polymers at interfaces and extended defects

By using the Green's function approach we consider the adsorption of a Gaussian polymer chain on a flat attractive interface separating two different media. The asymmetry of the potential requires a finite attraction for adsorption. We have calculated the size of the polymer in the direction perpendicular to the interface for arbitrary chain length. We also consider the adsorption of a self-avoiding polymer on a penetrable cylinderlike and spherelike defect. The method used enabled us to describe the adsorption below the threshold temperature Tc. We predict scaling of the crossover chain length Nc just below Tc of the formNc{~}(Tc-T)^-1/φ. The crossover exponent {φ} is given by {φ}={ν}d-1 with d=2,3 for the case of the cylinder and the sphere, respectively. The expression, which we derive for Tc, shows that increasing the solvent quality lowers Tc and may therefore cause polymer desorption. {} 1996 The American Physical Society.