Interpenetration of two polymer chain globules

Molecular dynamics was performed in a model system of two chain globules so that a process of the two globules merging was just simulated. It was found that this merging process was recognized as two stages, the wetting stage and the interpenetration stage. The interpenetration does not occur to partially encountered segments of the two globules, even though the chain segments are in the molten state. In the first stage, the touched two globules change their shapes rapidly from a sphere to a half-ball respectively. This obviously shows that the change in shape is mastered by the surface tension. In the second stage, the interpenetration happens to the two-chain sphere with an initial structure of each chain in a half-ball shape. A different molecular mechanism of chain diffusion has been found for this system. It is the chain loop crawling among the globule surface. Characterization of the interpenetration process was carried out by several means of analyzing the trajectory files. It was found that in the interpenetration stage there is a fast evolution and a lentitude period. The interpenetration is a conformational entropy driving process, and takes a half time for the lentitude period, which regards just 15% of total free energy difference.