Simulation of the intrinsic viscosity of hyperbranched polymers with varying topology. 1. Dendritic polymers built by sequential addition

Abstract

Hyperbranched polymers obtained from sequential addition of AB2 monomers to a B3 core are simulated to determine the intrinsic viscosities [η]of hyperbranched polymers with various degrees of branching. A simple hydrocarbon model for the molecules is used together with an RIS Metropolis Monte Carlo procedure which reproduces the experimentally observed properties of linear chains in a theta solvent ([η]αM0.5) and of perfect dendrimers (a peak in the plot of log [η]versus log M). This model, applied to hyperbranched materials, suggests that they should show a similar maximum in [η] at readily achievable branching ratios. It is shown that the degree of branching, despite a recent redefinition, is not an adequate descriptor for the shape of dendritic molecules. The Wiener index of the connectivity tree of a hyperbranched structure, however, shows a near perfect power law correlation with the simulated intrinsic viscosities of molecules with the same molecular weight but different topologies.