Preparation And Property Characterization Of Theophylline Molecularly Imprinted Polyimide Nanofiber Membrane

In this paper,THO molecularly imprinted polyimide nanofiber composite membrane(PIMIM)was prepared through a two-step method,which includes pre-coated functional monomer polymer and thermally initiated cross-linked polymeric reaction on the surface of polyimide nanofiber membrane(PIM),the base membrane,using theophylline(THO)as template molecule,methacrylic acid(MAA)as functional monomer,ethylene glycol dimethacrylate(EDMA)as crosslinker,azobisisobutyronitrile(AIBN)as initiator,and chloroform(CHCl3)as the solvent.To optimize the preparing and operating conditions,the PIMIM was encapsulated into laboratory-made assemblies and its parameters such as permeability and separation performance were investigated.Results were as follows:Firstly,polyimide nanofiber membrane(PIM)was obtained by temperature programmed heat treatment,dehydration reaction of polyamic acid nanofiber membrane(PAAM),which was prepared by electrospinning method.When conditions such as 300.0 r/min of the drum rotation rate,40 cm/min of the moving speed of the electrospinning needle and 12.0 h of the electrospinning time were unchanged,the preferred electrospinning conditions were as follows:15.0 kV of spinning voltage,0.5 mL/h of dope flow,and 12.0 cm of receiving distance.Secondly,the pre-coating PMAA ethanol solution on the surface of PIM,the base membrane,was dried and treated by thermal free-radical crosslinking reaction,through which PIMIM was prepared.PMAA coating amount was converted into molar amount of MAA,n(MMA#).Mass fraction w(PMAA)of PMAA solution,and solutes proportion before crosslinking reaction in the solution was optimized to obtain better conditions:w(PMAA)=0.08,V(CHCl3)=10.0 mL/0.5 mmol THO,n(THO):n(MMA#):n(EDMA):n(AIBN)=1:3.9:20.7:0.4.Finally,the comprehensive performance of PIMIM was discussed though static adsorption and dynamic permeation experiments.When the feed temperature was 20?,PIMIM showed a larger adsorption binding capacity for THO(0.1437 mmol/g),and a relatively smaller adsorption binding capacity for TB(0.0997 mmol/g),which indicated that the adsorption selectivity factor was up to 1.44.When the feed was 20? of temperature,1.0 mmol/L of concentration,12.5 mL/min of flow rate,PIMIM showed a maximum separation factor of 1.96 in a ethanol solution of THO and TB.The attenuation rate of separation factor of PIMIM was investigated after it was reused 2 to 3 times,and it was found that Soxhlet extraction was superior to ultra sound elution,both of which were elution methods of template molecule.