Distribution of a polymer chain between two interconnected spherical cavities

The equilibrium distribution of a polymer chain between two interconnected spherical cavities (a small one with radius R_s and a large one with radius R_l) is studied by using Monte Carlo simulation. A conformational transition from a double-cavity-occupation (DCO) state to a single-cavity-occupation (SCO) state is observed. The dependence of the critical radius of the small cavity (R_sC) where the transition occurs on R_l and the polymer length N can be described by R_\rmsC\propto N^1/3R_\rml^1-1/3\nu with ν being the Flory exponent, and meanwhile the equilibrium number (m_s) of monomers in the small cavity for the DCO phase can be expressed as m_s = N/((R_l/R_s)³ + 1), which can be quantitatively understood by using the blob picture. Moreover, in the SCO phase, the polymer is found to prefer staying in the large cavity.