Simulation On The Diffusion Motion Of New Polymers Using Monte Carlo Method

Modern polymer dynamics theory and rheology theory are important basis for studying polymers.In this thesis,we focus on the dynamics and Rouse chain relaxation of non-entangled polymers.Reptation is an important feature of the entangled polymer relaxation process,and the tube theory plays an important role in entangled polymer.A simple model of ionomers,namely a single polymer chain in a series of fixed attractors.In analogy to ionized beads claws of surrounding chains,the set of attractors can affectively slow down the diffusion motion of the target chain.the monomer meansquare displacement of ionomers is studied by using Monte Carlo algorithm,and compared with the prediction of the sticky Rouse model.The diffusion motion properties of ionomers are explored in three aspects,including the chain length of the polymer,the depth of the potential well,and the number of ionic groups.The results show that a plateau appears in the monomer diffusion function due to the attraction of the attractors to the claws.However,comparative theoretical predictions and simulation results show that there exist some discrepancy between them.Therefore,the relaxation time distribution of polymer chain motion is explored.The simulation results confirm that the association lifetime is decreasing with exponential,and the expected values of the association lifetime satisfy the Boltzmann distribution is told by the results.These results perfectly explain the deviation between the simulation data and the theoretical results.Unentangled ring polymers take a Rouse-like relaxation process,which is shorter than the relaxation time of the linear chain of the same length.However,the relaxation time of the entangled ring-shaped polymer is still under debate since the polymer has their no free end.The physical properties of an entangled polymer chain can be obtained by a single polymer chain via establishing a mesh model.We have simulated the diffusion motion of the circular chains,and obtained the relaxation times by using three different methods.Four different scaling models have been proposed to predict the scaling exponents for the dynamics of nonconcatenated entangled rings.And our results are coincide with the FLG model.At the same time,we also compare the difference between linear and circular chains,including relaxation time and diffusion motion.Indicated by our simulation results for same length of the chains,the plateau of g2(t)for ring chains are below that of linear polymers,and the relaxation times of the ring chains are shorter than that of linear polymers show by simulation results which are completely consistent with theoretical results.