Adsorption Profiles of Long-Chain Polymer in Semidilute Solutions Physisorbed to a Wall Peter Cifra Polymer Institute, Slovak Academy of Sciences, Du ´bravska ´ cesta 9, 842 36 Bratislava, Slovak Republic Fax: þ421-2-54775923; E-mail: upolpcif@savba.sk Keywords: adsorption; concentration profile; molecular simulations Introduction Polymer adsorption is the underlying process in various applications such as controlling aggregation properties in colloidal stabilization, surface protection, coating, lubrica- tion, adhesion, etc. Generally, macromolecules interact with surfaces or interfaces very strongly. A typical situation can be described either as a repulsion of macromolecules at surfaces, which is usually of entropic nature, or as a strong adsorption, which appears because even a small preferential adsorption of a chain segment adds up to a huge preferential adsorption of the whole chain. Adsorption of macromole- cules with its rich structural behavior, including chain loops, trains and bridges on the adsorbing surface, is treated in detail in several papers and reviews, [1–8] which also include various theoretical approaches to macromolecular systems at interfaces. Scheutjens and Fleer [1] designed a detailed self-consistent mean-field (SCMF) theory for macromolecular adsorption. This mean-field treatment, however, ignores correlations in solution and is, in this respect, supplemented by the scaling approach of de Gennes. [3,4] Except from the original scaling approach, based on a powerful scaling argument, a more detailed scaling approach was designed recently by Auboy, Guiselin and Raphae ¨l, [9] which is based on a population of loops and trains. Recently, experiments are also able to provide detailed microscopic information on the adsorbed macro- molecules. [5,10–12] Since adsorption of macromolecules involves barriers with high energy between adsorbed states, special attention is paid to the dynamics of these processes. [5,13] Finally, molecular simulations can provide more insight based on independent and microscopic information. [13–16] This is especially true for the strong adsorption we are interested in. While the strong adsorption Full Paper: Equilibrium concentration profiles for long macromolecules in solution strongly adsorbed to a flat wall were estimated by a combination of persistent reptation and partial chain regrowth using a configurational bias lattice Monte Carlo method. The profiles were obtained for various concentrations in the semidilute regime and different chain lengths. A master curve exists in a plot of the profile reduced by the bulk concentration as a function of the distance to the wall reduced by the correlation length estimated for the bulk concentration. Near the wall, the master curve follows a power law with an exponent predicted in the scaling theory. Compared to depletion profiles at a repulsive wall that require a small penetration length, no correction of the distance to the wall is needed for the adsorption profiles. Reduced plot of f(x)/f bulk vs. x/x for chain length N ¼ 1 000 and five bulk concentrations above f* indicated in legend. Slope with the exact exponent from scaling theory is shown for comparison. 270 Macromol. Theory Simul. 2003, 12, 270–275 Macromol. Theory Simul. 2003, 12, No. 4 ß WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2003 1022-1344/2003/0405–270$17.50þ.50/0