Co-authors​ :

 Samuel MANDIN (FRANCE), Lorenzo METILLI , Bruno JEAN , Nicolas HENGL , Frédéric PIGNON (FRANCE) 

The number of techniques for the fabrication of cellulosic nanocomposites has been growing in recent years. Nevertheless, it is necessary to control the organization of nanoparticles in order to confer mechanical, optical or barrier properties to these composites. To this end, the use of a ultrafiltration process combined with ultraviolet (UV) crosslinking has proven to be an innovative method. Indeed, ultrafiltration, owing to the combined application of pressure fields and induced flows near the membrane, allows the structuring and orientation at the nanoscale of nanoparticles such as cellulose nanocrystals (CNC) [1-2]. However, if the pressure is released, the structuring induced under pressure could be lost. In order to preserve the pressure-induced organization, fixing it under pressure is mandatory. That is why, in this paper, the introduction of a photocurable polymer, a poly (ethylene glycol) diacrylate polymer (PEGDA), enabled to fix the structure present during the filtration. Using such a strategy, a PEGDA/aqueous CNC suspension in 70/30 mass ratio was successively submitted to frontal filtration and then UV-cured in the dedicated filtration/curing cell. This procedure has allowed the design of nanocomposites with well-oriented and densely packed CNCs, homogenously distributed in a PEGDA matrix over a length-scale of ca. 500 microns. Small Angle X-ray Scattering (SAXS) characterization of the nanocomposites revealed the orientation of the CNCs parallel to the membrane surface with an increasing alignment level following the increase in concentration towards the membrane . Electron microscopy showed the presence of a lamellar-type structure in the form of sheets regularly spaced in the direction of application of the transmembrane pressure, with a chiral nematic (cholesteric) organization of the CNC displaying an increasing pitch gradient from the membrane surface to the bulk.