Synthesis, characterization and viscoelastic properties of Nanocrystalline Cellulose grafted with Poly(N-isopropylacrylamide)

U.D. Hemraz, C. Danumah, A. Lu, Y. Boluk
National Institute for Nanotechnology, University of Alberta, CA

Keywords: nanocrystalline cellulose, polymer grafting, poly(N-isopropylacrylamide), rheology


Nanocrystalline cellulose (NCC) is a renewable, nontoxic and biodegradable nanomaterial that can be obtained by acid hydrolysis of the amorphous regions of the widely available cellulose. The relative low density, low cost, high aspect ratios, high surface area, potential for surface modification, unique morphology and mechanical properties makes NCC a very attractive material. Since NCC has a hydrophilic nature, its application is limited. As such, the surface modification of NCC is a convenient way to increase the versatility of this material. In this work, we grafted NCC with N-isopropylacrylamide (Nipaam) via living radical polymerization, to express the thermo-responsive poly(Nipaam) grafts on periphery of the NCC surface. Various techniques were used to characterize the physical, chemical, morphological, thermal properties of the resulting materials. The shear viscosity of unfunctionalized NCC suspension decreased slightly with an increase in temperature from 20oC to 45oC, indicating a stable system. For the Nipaam-g-NCC, the storage modulus and shear viscosity values both exhibited a burst increasing at about 32oC, which is assigned to be the lower critical solution temperature of Nipaam, indicating successful functionalization of Nipaam on NCC. A thermodynamic property was introduced in the functionalized NCC, after grafting with Nipaam.