Grafting of Polycaprolactone on Oxidized Nanocelluloses by Click Chemistry

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.