A NEW SIMULATION METHOD FOR THE DETERMINATION OF FORCES IN POLYMER COLLOID SYSTEMS/

We introduce a new simulation method, which we call the contact-distri bution method, for the determination of the Helmholtz potential for po lymer/colloid systems from lattice Monte-Carlo simulations. This metho d allows one to obtain forces between finite or semi-infinite objects of any arbitrary shape and dimensions in the presence of polymer chain s in solution or physisorbed or chemisorbed at interfaces. We illustra te the application of the method using two examples: (i) the interacti on between the tip of an atomic force microscope (AFM) and a single, e nd-grafted polymer chain and (ii) the interaction between an AFM tip a nd a polymer brush. Numerical results for the first two cases illustra te how the method can be used to confirm and extend scaling laws for f orces and Helmholtz potentials, to examine the effects of the shapes a nd sizes of the objects and to examine conformational transitions in t he polymer chains.