Cellulose nanofibrils as templates for the design of poly(l-lactide)-nucleating surfaces

The abilities of surface-grafted cellulose nanofibrils for the nucleation of poly(l-lactide) (PLLA) were investigated. Cellulose nanofibrils with a width of ∼3 nm were obtained from wood cellulose via the oxidation using 2,2,6,6-tetramethylpiperidiniyl-1-oxyl as a catalyst and successive mechanical treatment. The cellulose nanofibril surfaces were selectively modified with amine-terminated poly(ethylene glycol) chains, via simple ionic bonds. The PEG-grafted cellulose nanofibril/PLLA composite films were prepared using a solvent casting method with chloroform. The isothermal and non-isothermal crystallization kinetics of the PLLA in the composites was studied using differential scanning calorimetry and polarized optical microscopy. The PEG chains were densely immobilized on the surface of the cellulose nanofibril templates, which had extraordinarily large specific surface areas. As a result, the surface-PEG layers effectively increased the rate of crystallization of the PLLA in the composites. Because of the increased degree of crystallinity after the isothermal crystallization, the composites showed better heat resistance than neat PLLA.