Development of Functionalized Nanocrystalline Cellulose-Based Polyelectrolytes with High Water Uptake

Dicarboxylate nanocrystalline cellulose (DCNC) polyelectrolytes were prepared from nanocrystalline cellulose (NCC) by introducing carboxylate units at the C-2 and C-3 positions of a glucose moiety through a two-step selective oxidation process. The polyelectrolyte nature of the DCNC was investigated by measuring the water uptake capacity with a customized ion exchange system. The equilibrium water uptake capacity of DCNC was almost ten times greater than that of conventional C-6 functionalized monocarboxylated NCC. The conversion of NCC to DCNC ensured the presence of a large number of dissociable electrolytic ions and high degrees of conformational freedom in the material to generate high osmotic pressure. Conductivity and dynamic light-scattering measurements were performed to relate the water uptake capacity with the chemical and structural changes of the polyelectrolytes. Furthermore, it was observed that the ionic strength of the solution played a critical role in controlling the water uptake capacity of the material.