Novel non-linear polymers
Aiming to reduce costly experimental trials and errors in the polymer industry, PMILS addressed the issue of effectively predicting the macroscopic properties of polymer materials. Based on knowledge of molecular constitution and processing history, researchers developed suitable methodologies and tools for polymer molecular modelling. One of the project results involved a state-of-the-art Monte Carlo algorithm for the simulation of long chained polyethylene melts with a linear and a non-linear molecular architecture. The algorithm is based on an advanced set of chain-connectivity altering moves and may be used for both mono- and poly-disperse systems. H-shaped polyethylene systems that include polyethylene chains with a main backbone trapped between two branch points, each of which is linked to two dangling arms, were used for testing purposes. The test results offered numerous uncorrelated and fully equilibrated configurations at all length scales for subsequent molecular dynamics studies. Apart from the rigorous estimates of the thermodynamic and conformational properties of H-polymers, the algorithm was also found capable of accurately predicting several key properties. These included branch point friction, diffusivity of chain centre-of-mass, spectrum of relaxation times and zero shear rate viscosity. The key innovative aspect with the new code rests in its ability to simulate the viscoelastic properties of polymers bearing long/short branches along their backbone. The algorithm would be very useful in non-equilibrium molecular dynamics simulations when interpreting the strain-hardening properties of branched polyethylene melts. In addition, it may be able to prove the better performance of branched polymers in fluid-flow processing operations in comparison to linear ones.
