| The complexity of the molecular and supramolecular structures of lignocellulosic polymers makes their direct study difficult. One of the ways to overcome this issue and to simplify the experimental approaches is the use of model compounds and pure thin films. Specifically, to facilitate fundamental studies related to surface phenomena if flat, ultra-thin films are used in combination with appropriate analytical tools. Model surfaces of cellulose, lignin and cellulose-lignin blends were prepared by different deposition techniques; i.e. cellulose nanocrystals (CNCs) obtained from acid hydrolysis were used to prepared isotropic and anisotropic monolayers by the Langmuir-Schaeffer (LS) and convective assembly techniques, respectively. Cellulose-lignin blend polymer thin films were spin coated on solid supports. All of these films were characterized with surface sensitive technique.;For isotropic LS-CNCs films, dioctadecyldimethylammonium bromide (DODA-Br) cationic surfactant was used to create CNC-DODA complexes that allowed the transfer of CNCs from the air/liquid interface in an aqueous suspension to hydrophobic solid substrates. Overall, the films obtained with this technique were shown to be smooth, stable and strongly attached to the solid support. The packing density of the films can be controlled by selecting the right combination of surface pressure during transfer to the solid substrate and the amount of CNCs available relative to the cationic charges at the interface.;The convective assembly setup used to align the CNCs was found to be simple, inexpensive and potentially scalable. It was elucidated that contributions of shear and capillary forces are primarily responsible for the alignment. The coupling of low electric field to the convective assembly setup was found to improve the alignment of CNCs. It is expected that these two model films can be used to study the properties of aligned CNCs, e.g. piezoelectricity.;Finally, ultrathin bicomponent films of a cellulose and lignin derivatives were deposited on silica by spin coating and employed as enzymatic sensors after regeneration to cellulose and lignin. The complex role of lignin in the enzymatic hydrolysis of lignocellulosic material was investigated and its inhibition effect was attributed to hydrophobic interactions between cellulases and the lignin domains. This effect was quantified by using kinetic models. The new platform proposed to monitor cellulolytic reactions in bicomponent films efforts is expected to help to further understand the complex phenomena that occurs in lignocellulose biomass conversion. |
