Molecular Dynamics Study On The Memory Effect Of A Polyethylene-Like Liner Polymer Model

Due to the excellent properties and wide applications,polymer materials are of great interest of researchers and engineers.The existence of crystallinity makes significant difference in properties in hemi-crystalline polymer compare to amorphous polymers.Macromolecule chains have high-degree integration and interpenetrate,which make it difficult to investigate.Thus crystallization of polymer is always one of most challenging process to investigate in macromolecular physics.Polymer crystals are structures that are not thermal equilibrated and the properties are greatly influenced by the kinetic pathways applied during the crystallization process,which makes real-time study more important.Although traditional experimental methods constructed the fundamentals of polymer crystallization theory,there are natural limitations in experimental apparatus.And the numerical simulation opens another door for researchers in this area,especially in investigating the microscopic structure evolution in crystallization.Molecular dynamics simulation was used to establish a polyethylene-like liner polymer model and research crystallization memory effect.The experimental results showed that the dynamic structure of polymer chains fit fold-chain model proposed by Keller and Fischer.Some polymer chains fold near neighbor loosely and some chains fold cross layer at original state.The system presents a state that polymer chains fold regularly near neighbor when reach equilibrium.Then we studied how melting temperature and melting time affect melting memory by crystallization behavior after different melting process.In addition we have used VMD and order parameter to investigate how melting temperature and melting time affect structure of polymer chain at the begging of crystallization.The numerical model is verified by comparing the numerical model and experimental data reported in literature.It showed that the molecular dynamics simulation can qualitatively represent the memory effect of polymer on crystallization and reveal the micro-/macroscopic structure during that process.