Fabrication and characterization of mats made of soft LbL nanotubes

In natural tissues, nanofibrillar networks have an important role as support, to control crystallization processes or guide motion, mostly due to both their structure and the numerous possible chemical interactions of their building elements. These observations have inspired the development of mats of nanofibers or nanotubes incorporating synthetic materials and numerous functional macromolecules. In the present work, a new method is proposed to obtain mats of nanotubes based on, first, the production of nanotubes by combining the membrane-templated strategy and layer-by-layer (LbL) adsorption and, subsequently, the filtration and sedimentation of the nanotubes over a substrate. In this context, the main objective of this work is to investigate the building process of mats from the nanotubes and its control parameters by characterizing the morphology and the physical properties (Young's modulus) of the mats as a function of some varying parameters (number of bilayers of the nanotubes, degree of humidity, quantity of nanotubes, diameter of the nanotubes). This study is performed for nanotubes made of poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) polyelectrolytes with also a brief investigation of the PAH and poly(acrylic acid) (PAA) combination. We show that mats of well-defined nanotubes can be obtained provided proper conditions are used, and that it is possible to stack mats made of different nanotubes to obtain more complex systems. First measurements of the Young's modulus of the mats provide values of ca. 100 MPa, close to what is expected for multilayers made of the same polyelectrolytes.