Microscopy and rheological studies to characterize the dynamical properties of colloidal networks based on transamination dynamic bonds between cellulose nanofibrils

• Grant number: 25/10394-3
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: September 29, 2025
• End date: September 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Camila Alves de Rezende
• Grantee: Thais Cardoso de Oliveira
• Supervisor: Francois Genes Tournilhac
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: ParisTech, France
• Associated to the scholarship: 22/05465-0 - Reprocessable and natural polymeric networks based on dynamic covalent bonds between cellulose nanofibers, BP.DR

Abstract

This doctoral project aims to design cellulose nanofibrils (CNF)-based gel vitrimers formed by dynamic covalent crosslinking of enamine-functionalized CNF, which can undergo transamination when the material is heated, enabling re-processability and recyclability even after chemical crosslinking, thereby maintaining CNF green features. Halfway through this project, the CNF enamine functionalization is under development as the synthesis of dynamic enamine molecules and the extraction/thiol functionalization of the CNF have been successfully performed. Investigating the characteristic properties of a vitrimer is the next step to determine to what extent the formed network is crosslinked by covalent adaptable bonds and to evidence specific features associated with the multiple-scale structure of this new type of vitrimer. The targeted methodology involves the characterization of macroscopic mechanical behavior, mesoscopic deformation patterns, and microscopic dynamics under yielding, using rheology measurements and optical microscopy. Therefore, in this BEPE project, we aim to thoroughly examine the potential CNF-based organogel vitrimer by rheo microscopy with advanced techniques such as differential dynamic microscopy (DDM) for assessing the microstructural properties of the material. The chemistry and physics of vitrimers is an area of excellence of the host laboratory: Laboratoire de Chimie Moléculaire, Macromoléculaire, Matériaux (C3M), at École Supérieure de Physique et Chimie Industrielles (ESPCI-Paris-PSL). The C3M lab was at the origin of the very concept of vitrimer in 2011. Since then, the host supervisor's group has been developing new methodologies dedicated to advanced vitrimer studies. The ESPCI and Unicamp partnership started in 2021, aiming to develop nanocellulose-based vitrimers. Their collaboration encompasses the core concept of the current PhD project, which is linked to this BEPE proposal. Ultimately, the activities proposed in this internship will increase the relevance and impact of this PhD work, providing a deeper understanding of this multiscale vitrimer concept based on sustainable materials.