Fabrication of flexible, aligned carbon nanotube/polymer composite membranes by in-situ polymerization

Vertically aligned (VA) carbon nanotubes (CNTs) have shown orders of magnitude enhancement for gas and liquid flow compared to conventional mass transport theories. Flexible, large surface-area VACNT membranes may provide a cost-efficient solution to various separation processes such as water purification and gas separation. However, all the VACNT membranes produced so far suffer from rather small membrane area, long fabrication process, poor mechanical stability, local agglomeration of CNTs, and low CNT packing density. Here, we present flexible, VACNT/polymer composite membranes having relatively densely packed CNTs as the only mass transport paths. In order to prevent CNT condensation that could disturb CNT orientation during liquid phase processing, we developed a novel in-situ bulk polymerization method to prepare VACNT/polymer composite films. A VACNT array was infiltrated with styrene monomer with a certain amount of polystyrene–polybutadiene (PS–PB) copolymer that acts as a plasticizer. Indeed, micro-indentation measurements confirmed that the addition PS-b–PB copolymer into the matrix improved the elongation at break of the CNT/PS composite film. SEM images showed that well aligned CNTs were embedded in a high-density polymer matrix free of any macroscopic voids or structural defects. Measured fluid rates and selectivity for gas and liquid mixtures are consistent with CNT membranes produced with different methods. These CNTs/polymer composite membranes showed high gas and water permeability comparable to the other VACNT composite membranes, potentially enabling applications that may require membranes with high flux, flexibility and durability.