Molecular dynamics study of polymeric chemical gels: Effect of persistence length and crosslinker density

Abstract

Using molecular dynamics, we study the formation of chemical gels from an initial solution of reactive polymers that undergo a crosslinking reaction. We study the effect of the polymer persistence length and different densities of crosslinkers along the chains. As the reaction progresses, different structural features are identified in the system leading to the development of a percolated cluster. These features are (a) single strands, (b) double strands, and (c) bridges. We found that the total numbers of these three kinds of features are roughly independent of the persistence length; however, the average lengths of single and double strands grow with this variable. The average length of double strands strongly increases with increasing crosslinker density and the amount of single strands sharply falls as crosslinker density grows. We also found that general structural features of polymer networks are highly dependent on chain persistence length and crosslinker density. Fully flexible chains with high density of crosslinkers result in inhomogeneous network structures with large voids. In contrast, precursor chains with high rigidity and scarce number of crosslinkers result in homogeneous networks having small cavities.