(5c) Applications of Ionic Liquids in the Synthesis of Polymeric Films with Novel Porous Structures

Authors: 
Huang, C., New Jersey Institute of Technology


Polyurea and nylon 610 with exotic porous structures were synthesized by interfacial polymerization (IP) between n-hexane and a series of 1-alkyl-3-methylimidazolium room temperature ionic liquids (ILs). Scanning Electron Microscopy (SEM) showed macroporous morphology of aggregated polymer particles with sizes around 20-200 nm and pore sizes between 50 to 500 nm in the polymer films. The geometry of the polymer particles and the pore size varied with the ILs employed. X-ray diffraction (XRD) showed ionic-liquid induced suppression of 3D crystalline order; small angle X-ray scattering (SAXS) shows peaks corresponding to a correlation length of 20nm. The microstructures of the polymer together with the Fourier Transform Infrared Spectroscopy (FTIR) results suggest the observed exotic polymer morphology originates from interactions between the ionic liquid and the polymer. The formation kinetics of nylon 610 films in ILs was studied by measuring the product mass and intrinsic viscosity. Polymer films ceased to grow in the late stage of the reaction due to the increasing diffusion barrier. The characteristic time marking the cease of the growth was found to be dependent on the initial reactant concentrations. The increase of polymer molecular weight with reaction time was monitored by intrinsic viscosity measurement. It is found that the molecular weight leveled off faster than the film growth under the same reactant concentrations. Based on our experimental studies, a simplified diffusion-controlled mathematical model was developed where the effective diffusivity in the polymer film decayed with the square of time. The model was used to fit the measured growth rate of the polymer film; the fitting results showed a conspicuously good agreement between the model and the experimental data.