Emily G Facchine1, Long Bai2, Orlando J Rojas3, Saad A Khan4. 1. Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA. 2. Department of Byproducts and Biosystems, School of Chemical Engineering, Aalto University, FI-00076 Aalto, Espoo, Finland; Bioproducts Institute, Departments of Chemical and Biological Engineering, Chemistry and Wood Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada. 3. Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA; Department of Byproducts and Biosystems, School of Chemical Engineering, Aalto University, FI-00076 Aalto, Espoo, Finland; Bioproducts Institute, Departments of Chemical and Biological Engineering, Chemistry and Wood Science, University of British Columbia, Vancouver, BC V6T 1Z3, Canada. Electronic address: orlando.rojas@ubc.ca. 4. Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA. Electronic address: khan@eos.ncsu.edu.
Abstract
HYPOTHESIS: Nanocellulose and nanochitin are both biobased materials with complementary structures and properties. Both exhibit pH-dependent surface charges which are opposite in sign. Hence, it should be possible to manipulate them to form complexed structures via ionic bond formation at prescribed pH conditions. EXPERIMENT: Nanocellulose and nanochitin were mixed after exposure to acidic or neutral conditions to influence their ionization state. The heat of interaction during the introduction of nanochitin to nanocellulose was monitored via isothermal titration calorimetry. The strength and gel properties of the resulting structures were characterized via rheological measurement. FINDINGS: The resultant gel properties in the designed hybrid systems were found to depend directly on the charge state of the starting materials, which was dictated by pH adjustment. Different interparticle interactions including ionic attraction, hydrophobic associations, and physical entanglement were identified in the systems and the influence of each was elucidated for different conditions of pH, concentration, and ratio of nanochitin to nanocellulose. Hydrophobic associations between neutralized nanochitin particles were found to contribute strongly to increased elastic modulus values. Ionic complex formation was found to provide enhanced stability under broader pH conditions, while physical entanglement of cellulose nanofibers was a substantial thickening mechanism in all systems.
HYPOTHESIS: Nanocellulose and nanochitin are both biobased materials with complementary structures and properties. Both exhibit pH-dependent surface charges which are opposite in sign. Hence, it should be possible to manipulate them to form complexed structures via ionic bond formation at prescribed pH conditions. EXPERIMENT: Nanocellulose and nanochitin were mixed after exposure to acidic or neutral conditions to influence their ionization state. The heat of interaction during the introduction of nanochitin to nanocellulose was monitored via isothermal titration calorimetry. The strength and gel properties of the resulting structures were characterized via rheological measurement. FINDINGS: The resultant gel properties in the designed hybrid systems were found to depend directly on the charge state of the starting materials, which was dictated by pH adjustment. Different interparticle interactions including ionic attraction, hydrophobic associations, and physical entanglement were identified in the systems and the influence of each was elucidated for different conditions of pH, concentration, and ratio of nanochitin to nanocellulose. Hydrophobic associations between neutralized nanochitin particles were found to contribute strongly to increased elastic modulus values. Ionic complex formation was found to provide enhanced stability under broader pH conditions, while physical entanglement of cellulose nanofibers was a substantial thickening mechanism in all systems.
Authors: Rubina Ajdary; Guillermo Reyes; Jani Kuula; Eija Raussi-Lehto; Tomi S Mikkola; Esko Kankuri; Orlando J Rojas Journal: ACS Polym Au Date: 2021-12-10