KSEF R&D Excellence: Synthetic Route for Carbon Nanotube Based Permeable Membrane

Control of pore size is critical for membrane separation processes. With membranes based on transport through carbon nanotubes (CNTs), of possible inner diameters ranging from 0.5 to 20nm, a large variety of compounds can be separated. These range from gases for fuel ceIl/environmental applications to large biologically active molecules with medicinal applications. Two critical difficulties that must be addressed are a) control of CNT inner diameters and b) the fabrication of a suitable polymer film with CNTs that efficiently traverse the thickness ofthe film. To control the CNT inner wall diameter, nano-crystalline (nc) Si02 will be coated with Fe catalyst. The diameter of the nc-Si02 catalyst support would determine the resultant CNT diameter and thus the pore size. Proposed is an innovative three-step process that would result in continuous CNT pore openings through the thickness of the membrane film; 1) CVD growth of inherently perpendicular CNTs on a thin glass substrate coated with nc- Si02/Fe catalyst 2) spin coating 1-5J.lmof low viscosity thermoset polymer to flow between CNTs and form a continuous film between CNTs and 3) removal of the thin Si02 substrate and nc-Si02 catalyst support with HF acid etch. This approach is a readily achievable combination of standard electronics thin film processing and nano-scale materials growth techniques. Further functionalization of CNTs utilizing carboxylic acid groups would allow for additional possibilities of chemical selectivity. A continuous high throughput process to form hollow fiber porous membrane could also be realized. Success in this project will enable many collaborative grant proposals since the wide range of possible membrane pore size would allow overlap with the interests of PI's involved with the UK Membrane Science Center. Through this enabling technology and resultant collaborative research to find suitable separation systems, there would likely be many emerging entrepreneurial opportunities.