Study On Highly Efficient Self-diffusion Of Polymer In Metal-organic Frameworks

The polymer optical waveguides with high optical anisotropy and low optical loss can offer unique functionalities for the optical transmission and information processing technologies in the future.However,the disorder of polymer chains and grains of polymer materials leads to a weak optical macroscopic anisotropy.Utilizing the periodically structured metal-organic framework?MOF?as the reaction vessel is a promising technique to achieve the aligned polymer molecular chains,where the diffusion procedure of the polymer monomer inside MOF is one of the key mechanisms.To investigate the diffusion mechanism of fluorinated polymer monomers in MOFs,in this paper the molecular dynamics simulations combined with the density functional theory and the Monte Carlo method are used and the all-atom models of MMA?methyl methacrylate?,TFMA?trifluoroethyl methacrylate?,PFMA?pentafluorophenyl methacrylate?monomer and four types of MOFs,[Zn₂?BDC?₂?TED?]_n?[Zn₂?BDC?₂TED]_n^non-charge?[Zn₂?BDC?₂TED]_n^45deg and[Zn₂?BPDC?₂?TED?]_n,are established.The diffusion behaviors of MMA and TFMA monomer in these four MOFs are simulated and the main influencing factors are analyzed.The obtained results are as follows.First,the electrostatic interactions between polymer monomers and MOFs cause the monomers to concentrate in the MOF channel,which slows down the monomer diffusion.Second,the anisotropic shape of the one-dimensional MOF channel leads to different diffusion speeds of monomers in different directions.Third,MOF with a larger pore diameter due to a longer organic ligand,[Zn₂?BPDC?₂?TED?]_n in this paper,facilitates the diffusion of monomers in the MOF channel.Fourth,as the number of monomers increases,the self-diffusion coefficient is reduced by the steric effect.These three factors have important influence on the selection of polymer monomer or MOFs,and provide a theoretical prediction method for the control of polymer chain orientation.