Interactions between surfactants and polymer-grafted nanocrystalline cellulose

The interactions between surfactants and nanocrystalline cellulose (NCC) grafted with a 600 Da polypropylene glycol (M600) were investigated by isothermal titration calorimetry (ITC) and nuclear magnetic resonance spectroscopy (NMR). The M600-grafted NCC prepared by reacting carboxylated NCC with amine-terminated M600 via a peptide coupling reaction, which was confirmed by infrared spectroscopy and transmission electron microscopy (TEM). Three types of surfactants with dodecyl alkyl chain and different head groups, namely cationic dodecyltrimethylammonium bromide (DoTAB), anionic sodium dodecyl sulfate (SDS), and nonionic poly (ethylene glycol) dodecyl ether (Brij 30) were studied. Strong electrostatic interaction was only observed between M600-grafted NCC and DoTAB, due to the binding of opposite charges. Hydrophobic interaction was displayed for the M600-grafted NCC/SDS system, and negligible interaction between M600-grafted NCC and Brij 30 was observed. Physical mechanisms describing the interactions of cationic, anionic and nonionic surfactants and M600-grafted NCC are proposed.