Molecular Design And Synthesis Of Membrane Materials For Aromatic/Alkane Pervaporation

Pervaporation is a clean and efficient membrane technology,which has great potential for the industrial application in the separation of aromatics/alkanes.The high-performance membrane materials are critical for the large-scale industrial application of aromatic/alkane pervaporation membrane separation technology,which are also one of the most active field of membrane science and technology.The"pore-filling"composite membrane has unique advantages in aromatic/alkane pervaporation separation.The separation performance is determined mainly by the functional filling polymer layer.According to the previous results of our group,the"pore-filling"composite membranes made from the polyethylene glycol methacrylate macromonomers with different end groups could have significantly different performance for the aromatic/alkane pervaporation.Design and synthesis of new polymers through molecular dynamics simulation is one of the effective ways to develop the high-performance polymeric membrane materials.In this work,a series of polyethylene glycol methacrylate macromonomers with different end groups were designed,which could be used for the fabrication of the"pore-filling"composite membrane for aromatic/alkane pervaporation.Materials Studio software was applied to simulate the sorption and diffusion behavior of toluene and n-heptane in the polymer designed.Based on the results of molecular dynamic simulation,the optimal end group was selected.The polyethylene glycol methacrylate macromonomer with the optimal end group was synthesized.The homopolymer was obtained via free radical polymerization.The homogeneous membrane was prepared by the solvent evaporation method,the aromatic/alkane adsorption selectivity was characterized by the swelling adsorption-desorption experiment.Firstly,a series of polyethylene glycol methacrylates with various end groups were built.The hydroxyl,methyl ether,amino,carboxyl,phenyl,maleimide,?-pyrrolidone,methylphenylsulfone,and N-acetylmorpholine were choosed as the end group.Materials Studio software was applied to construct the homopolymer models of polyethylene glycol methacrylate macromonomers,and to simulate the sorption and diffusion behavior of toluene and n-heptane.Furthermore,the toluene/n-heptane solubility selectivity,toluene/n-heptane mobility selectivity and toluene/n-heptane selectivity were calculated.It was found that,at353K,the toluene/n-heptane solubility selectivity of all the designed polyethylene glycol methacrylate polymer membrane materials are greater than 1,and the mobility selectivity are less than 1 which implied that the aromatic permselectivity of the polyethylene glycol methacrylate polymer was mainly determined by the solubility selectivity.Moreover,the toluene/n-heptane selectivity was changed obviously by the the end group.The N-acetylmorpholine-terminated polyethylene glycol methacrylate homopolymer has the highest toluene/n-heptane solubility selectivity and toluene/n-heptane selectivity,which are18.33 and 15.78,respectively.Secondly,based on the results of molecular dynamics simulation,2-?morpholin-4-yl?-2-methacrylate ethyl and N-acetylmorpholine terminal polyethylene glycol methacrylate macromonomer were successfully synthesized,which were characterized by the nuclear magnetic resonance hydrogen spectroscopy?¹H-NMR?,nuclear magnetic resonance carbon spectroscopy(¹³C-NMR),high-resolution mass spectrometry,matrix-assisted laser desorption ionization time-of-flight mass spectrometry?MALDI-TOF?and fourier transform infrared spectroscopy?FT-IR?,etc.Finally,the polyethylene glycol methacrylate macromonomers with three different end groups such as the hydroxyl end group,the methyl ether end group,and the N-acetylmorpholine end group were synthesized,and homopolymers were prepared via free radical polymerization.The homogeneous membranes were prepared by the solvent evaporation method.The toluene/n-heptane adsorption selectivity of the three kins of polyethylene glycol methacrylate macromonomers were obtained by the swelling adsorption-desorption experiments.It was found that,in the range of 313-353K,the toluene/n-heptane adsorption selectivity of N-acetylmorpholine-terminated polyethylene glycol methacrylate homopolymer is greater than those of hydroxyl group and methyl ether group terminated homopolymers,which is consistent with the results of molecular dynamics simulation.Moreover,the toluene/n-heptane adsorption selectivity of N-acetylmorpholine-terminated polyethylene glycol methacrylate homopolymer increased with temperature.At the temperature of 353K,the toluene/n-heptane adsorption selectivity was 20.44.