Simulation Study On The Conformation And Diffusivity Of Polymer In Crowded Environments With Periodically Distributed Nanoparticles

Polymer nanocomposites are widely used in various fields due to their excellent properties.The addition of nanoaprticles would significantly influence the conformation and dynamic properties of polymer chain.In this thesis,we study the conformation and diffusivity of a single polymer chain in a crowded environment with periodically distributed immobile nanoparticles by performing off-lattice Monte Carlo simulation.It is divided into two parts as follows:?1?Conformational statistical properties of polymer chain in the presence of periodically distributed immobile nanoparticles.We have investigated the effects of the chain length and inter-particle distance on the dimensions of polymer chain via annealing simulation.Results reveal that polymer dimensions at high temperatures are roughly close to that of free polymer chain.However,they can be increased or decreased at low temperatures and four typical behaviors are observed for the polymer in four different regions:?1?d<R₀/2;?2?d??R₀/2,R₀?;?3?d??R₀,2R₀?;and?4?d>2R₀.Here,R₀ is the end-to-end distance of polymer in dilute solution and d is the inter-particle distance.The dependence of polymer dimensions on T can be understood from the attraction between polymer and NPs at different temperatures.Our results show that the attraction of NPs plays an important role in the change of polymer dimensions.?2?Dynamic properties of polymer chain in crowded environment with periodically distributed immobile nanoparticles.We find that the diffusion coefficient D of polymer at low temperature is dependent on the inter-particle distance d and polymer length N or end-to-end distance of polymer in dilute solution R₀.At low temperature,D is large at both small and large d and a minimum is observed at intermediate d.The nonmonotonic behavior of D is due to the reason that there are two kinds of diffusion modes for the polymer at low temperature:NP-exchange motion for R₀>d and adsorption-and-desorption motion for R₀<d.Moreover,we observe the oscillation of D with N at a relatively low temperature.The novel behavior is explained from the free energy barrier for polymer jumping from the ground state to others.