Grafting of Polycaprolactone on Oxidized Nanocelluloses by Click Chemistry

Abstract

The main objective of this work is the grafting of polycaprolactone diol (PCL) on the surface of oxidized nanocelluloses (ONC) in order to enhance the compatibility between the hydrophilic cellulose nanofibres and the hydrophobic polymer matrix. This grafting was successfully realized with a new strategy known as click chemistry. In this context, the oxidized nanocelluloses bearing alkyl groups (ONC-PR) were prepared by reacting amino groups of propargylamine (PR) with carboxyl groups of ONC. In parallel, PCL was converted into azido-polycaprolactone (PCL-N3) in two steps: (i) tosylation of polycaprolactone (PCL-OTs) and (ii) conversion of PCL-OTs into PCL-N3 by nucleophilic displacement using sodium azide. Finally, ONC-PR was reacted with PCL-N3 in heterogeneous conditions through click chemistry in order to prepare polycaprolactone grafted oxidized nanocellulose (ONC-g-PCL), which could be suitable for improving the interfacial adhesion in the composite materials. The grafted samples were characterized by transmission electron microscopy and by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR) spectroscopic techniques.

Site-specific functionalization for chemical speciation of Cr(III) and Cr(VI) using polyaniline impregnated nanocellulose composite: equilibrium, kinetic, and thermodynamic modeling

“…Notably, we observed that, in the FTIR spectrum of NC, the O-H stretching band is shifted toward lower wave number (blue shifted) and become higher intense (hyper chromic) as endowed in Fig. 2a, confirming that during NC preparation, breakage of glucosidic bonds took place in pristine cellulose structure (Benkaddour et al 2013). This result evinces the successful preparation of NC.…”

Crosslinking of fibers via azide–alkyne click chemistry: Synthesis and characterization

“…Figure (b) shows a band around 2113 cm −1 , corresponding to the azide groups. When tosylated fibers reacted with sodium azide, the FTIR spectrum of azidated fiber showed the appearance of a new intense band typical of the azide groups, which clearly confirms that azide molecules covalently couple to the fiber chains . The FTIR spectrum of propargylated fiber in Figure (c) shows two new adsorption bands at 3286 cm −1 and 2119 cm −1 , corresponding to CH stretching and CC stretching, respectively, indicating the successful incorporation of terminal alkynes onto the fiber chains .…”

“…The strong hydrophilic nature of the fiber surface is the main reason why cellulose fiber is chemically modified . Cellulose fibers tend to agglomerate into bundles due to hydrogen bonds forming between the hydrophilic fibers, and they cannot be dispersed uniformly in most nonpolar polymer media . The most common approaches for cellulose modifications are esterification and etherification .…”

“…The chemistry of thiols is normally influenced by the basic structure of the thiol, whether radical or catalyst mediated . However, the classic radical‐based photopolymerization has several critical problems, including complex polymerization kinetics . Normally for both thiolyne and thiolene chemistry, the ‐ene or ‐yne structure dictates whether the reaction is chain‐transfer limited or not .…”

Nanocellulose reinforced as green agent in polymer matrix composites applications

“…160 This improvement is related to the rigidity of NC and the creation of accentuated fragility domains, which consequently increased the degree of crystallinity of the composites system. 161 However, the extent of mechanical reinforcement of NC in polycaprolactone matrix has been limited when its composition reached 12 wt%, due to the formation of nanocrystal aggregation during composites processing, derived from inter-particle interactions, which leads to the formation of weak points. This lack of intimate interface adhesion resulted in several irregular-shape microvoids within the composite.…”