Nanocellulose based hydrogel with tailored rheological properties by tuning the network architecture

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Journal Title
Journal ISSN
Volume Title
Kemian tekniikan korkeakoulu | Master's thesis
Date
2019-06-18
Department
Major/Subject
Fiber and Polymer Engineering
Mcode
CHEM3024
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
72 + 6
Series
Abstract
Cellulose nanofibrils (CNFs) is materializing into biomedical application research. Weak CNF hydrogels have been modified with various compounds in order to change the network architecture of this abundant biopolymer. This thesis seeks to understand the effect of CNF solids content in a coupling reaction. CNF was covalently modified with an amine containing thermoresponsive peptide terminated with tri (ethylene glycol) oxide and ionically modified with a quaternary ammonium containing peptide terminated with tri (ethylene glycol) oxide. Furthermore, the rheological behaviour of the CNF gels pre and post modification with the thermoresponsive chains was investigated. In the amide bond formation reaction on CNF, the highest degree of substitution (DS) on CNF-COOH was observed in a reaction condition with very low fibril consistency and the lowest DS was observed in a reaction condition with high fibril consistency, subsequently short time interval within reagent introduction. Moreover, in the ionic bond formation, higher DS was observed in reactions carried out at room temperature compared to the reactions done at higher temperature. CNF gels showed an elastic response throughout the measurement. However, covalently and electrostatically modified CNFs displayed a more solid-like character even at high frequency. Furthermore, unlike CNF gels that lose viscosity at higher frequency and temperature, the covalently modified CNF gels got stiffer with increasing temperature and the electrostatically modified CNF gels formed larger aggregates at higher temperatures, as observed by DLS. However, the stiffness observed in the covalently modified CNFs tend to become irreversible with decreasing temperature.
Description
Supervisor
Kontturi, Eero
Thesis advisor
Heise, Katja
Keywords
thermoresponsive, shear thickening, TEMPO-oxidised CNF, rheology
Other note
Citation