Abstracts Book - IMRC 2018

• SA6-P027
PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE
CELLULOSE BIREFRINGENT FILMS.
Tania Tejeda 1 , Arturo Mendoza Galván 1 , Reina Araceli Mauricio 1 , Amos Benjamín Domínguez
Gómez 1
1
Centro de Investigación y de Estudios Avanzados del IPN - CINVESTAV, Unidad Queretaro,
Mexico.
Cellulose is a natural biopolymer which is considered the most abundant in the
earth’s crust. It has a molecular structure that through a hierarchical
arrangement gives a fibrous macroscopic form with a semicrystalline character.
Its unique molecular and hierarchical structure leads to physical properties that
have found application in diverse fields. Furthermore, the large availability and
renewability of cellulose have motivated intense research to develop structured
materials for application in new areas. Particularly, cellulose nanocrystals (NCC)
based materials for optical applications are emerging. Therefore, in this work we
focus on the obtainment of birefringent films by isolation and purification of
NCC by acid hydrolysis of filter paper. Above a certain critical concentration, the
NCC adopt a liquid crystal phase in an aqueous suspension. NCC films on glass
substrates were obtained by dip-coating and dried at room temperature. Using
this method, it was expected that the NCC films in the suspension were aligned
in a preferential direction due to draining drag forces acting during the removal
of the substrate at a constant withdrawal speed. Atomic force microscopy
images corroborated the alignment of the NCC on the substrate. The
transmittance of unpolarized light of the NCC films in the visible spectral range
was close to 90%. Scanning electron microscopy images showed the thickness
of the NCC films ranges between 2 and 3 µm. The birefringence was evidenced
by placing the samples between an LCD monitor and a linear polarizer in the
extinction configuration. Spectroscopic ellipsometry measurements at normal
incidence were performed for different angles of rotation in the samples. The
measurements were analyzed with the Mueller matrix formalism assuming that
the sample behaves as a rotated retarder, thus obtaining birefringence values
ranging between 0.010 and 0.022 depending on the withdrawal speed and
concentration of NCC. These results are promissory for obtaining NCC
birefringent films by a simple and controllable method.