Abstract
Herein, we present a route to obtain bi-functional cellulose nanofibrils (CNF) by a one-pot approach using an already established functionalisation route, carboxymethylation, to which a subsequent functionalisation step, allylation or alkynation, has been added in the same reaction pot, eliminating the need of solvent exchange procedures. The total charge of the fibres and the total surface charge of the nanofibrils were determined by conductometric and polyelectrolyte titration, respectively. Furthermore, the allyl and alkyne functionalised cellulose were reacted with methyl 3-mercaptopropionate and azide-functionalised disperse red, respectively, to estimate the degree of functionalisation. The samples were further assessed by XPS and FT-IR. Physical characteristics were evaluated by CP/MAS 13C-NMR, XRD, AFM and DLS. This new approach of obtaining bi-functionalised CNF allows for a facile and rapid functionalisation of CNF where chemical handles can easily be attached and used for further modification of the fibrils.Graphical abstract
Highlights
Nanocellulosic materials, such as cellulose nanofibrils (CNF) have been given an increased interest during the past decades as components in bio-based and/or renewable composite materials (Dufresne 2012, 2013; Eichhorn et al 2001, 2010; Klemm et al 2011)
Carboxymethylation of cellulose fibres has been successfully combined with a subsequent functionalisation step (Williamson etherification), yielding a one-pot preparation method of functionalised carboxymethylated cellulose fibres (CM-Ffibre) and fibrils (CM-F-CNF)
A one-pot protocol for preparing bifunctional cellulose nanofibrils has been developed using the combination of both carboxymethylation of fibres in order to introduce charge and the concurrent conventional etherification incorporating an additional functionality, in this case alkenes or alkynes, which can be used for further modification of the cellulose nanofibrils
Summary
Nanocellulosic materials, such as cellulose nanofibrils (CNF) have been given an increased interest during the past decades as components in bio-based and/or renewable composite materials (Dufresne 2012, 2013; Eichhorn et al 2001, 2010; Klemm et al 2011). T. Larsson RISE Bioeconomy, Drottning Kristinas vag 61, 114 86 Stockholm, Sweden mostly attributed to their unique combination of comparably high strength and stiffness in combination with a low density compared to for example Kevlar or steel, and to the possibilities of producing these materials with lower consumption energy (Chauve and Bras 2014; Eriksen et al 2008; Klemm et al 2011). The high aspect ratio and large interfacial surface area of CNFs contributes to the development of functional composite materials with remarkable mechanical properties (Dufresne 2012; Eichhorn et al 2010). Due to the inherent hydrophilic nature of cellulose, CNFs have to be surface modified in order to adequately take advantage of their principal nano-reinforcing characteristics in hydrophobic polymer matrices
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