INTERACTION BETWEEN A GRAFTED POLYMER-CHAIN AND AN AFM TIP - SCALING LAWS, FORCES, AND EVIDENCE OF CONFORMATIONAL TRANSITION

The force of compression of an end-grafted polymer chain in a Theta so lvent by a finite-sized object (e.g., the tip of an atomic force micro scope) is studied using a new simulation technique called the contact- distribution method. This paper presents the first ever simulation of the conformational transition of a polymer chain from a ''confined'' s tate to an ''escaped'' state. The results corroborate the force relati ons that were recently obtained using scaling arguments but clearly in dicate the existence of a transition region between the two states. Th e characteristics of the transition are affected by the size, shape, a nd alignment of the tip and by the temperature or quality of the solve nt. We also comment on the implication of the results to the experimen tal confirmation of the predictions.