Compression and Escape of a Star Polymer

The problem of a polymer confined within a slit is a classic problem that is generally well understood.1,2 More recently, researchers have explored a related problem: a chain, end-tethered to a surface and com-pressed by an obstacle, e.g., the flat end of a cylinder, whose size is not much larger than the natural dimen-sion of the chain.3-13 When compressed weakly, the chain does not “see ” the edge of the compressing obstacle, it deforms uniformly, and the force that the chain imposes on the obstacle grows monotonically with compression. However, beyond a critical compression, the chain can reduce its energy by forming a stretched umbilical tether from the grafting point to the edge of the disk so that many of the monomers in the chain can “escape ” from underneath the compressing obstacle