Monte-Carlo simulation for the kinetics of collapse and phase separation in homopolymer solutions

We present preliminary results from a Monte-Carlo simulation in a lattice model of homopolymer solutions at various concentrations up to the semi-dilute regime. Two main simulation routines based on the Metropolis algorithm are implemented and these control the internal and global movements of each polymer chain, respectively. We study the kinetics of conformational changes after a quench to the poor solvent region. Each chain may collapse individually as well as aggregate with others, and the competition of both types of processes determines the conformational state. We visually observe and quantitatively analyse the formation of mesoglobules — nearly spherical aggregates consisting of a few distinct chains, recently observed experimentally in our laboratory, as a non-equilibrium state. The time scale during which the mesoglobules are preserved is found to be rather long compared to the collapse time of an isolated chain even for large quenches considered here. Our findings agree qualitatively with the results of both experimental and theoretical work carried out in our laboratory.