Rheology and structural properties of hyperbranched polymers: a non-equilibrium molecular dynamics study

Hyperbranched polymers are imperfectly branched or irregular tree-like structures that have special properties and potential applications in various areas such as thermoset resins, toughening agents and drug delivery. They can be synthesized economically by one-pot reaction which adapts well to large-scale production but provides a polydisperse mixture of randomly branched polymers with different size and topology. This leads to difficulties in experiments and gives simulation a valuable opportunity to gain further insight in understanding the structure and rheology of hyperbranched structures. They have been simulated using bead-rod models together with Monte Carlo and Brownian dynamics techniques. In this research, hyperbranched polymers were simulated using coarse-grained uniform beads and non-equilibrium molecular dynamics (NEMD) methods. Polymeric chains are composed of interconnected beads interacting via finitely extensible nonlinear elastic (FENE) and Weeks-Chandler-Anderson (WCA) potentials. Viscoelastic properties and structural changes of trifunctional hyperbranched polymers in the melt undergoing planar shear are investigated. Our results are in the range between those of dendrimers and linear analogues of equivalent molecular mass.