An environmentally benign methodology to elaborating polymer nanocomposites with tunable properties using core-shell nanoparticles and cellulose nanocrystals

An environmentally benign concept based on waterborne systems is developed for preparation of novel nanocomposite materials with tunable properties. The designed nanocomposites are based on combination of coreshell latex nanoparticles, cellulose nanocrystals (CNC) and polyethylene glycol (PEG). First, core-shell latex nanoparticles from copolymer (methyl methacrylate-ethylene glycol dimethacrylate)-core and copolymer (methyl methacrylate-butyl acrylate)-shell (CS15) are prepared by starved emulsion polymerization. Likewise, incorporation of CNC aqueous suspension into the core-shell latex without any further chemical modification of the nanofiller while assuring good compatibility between both entities is achieved. PEG is effectively added to the suspension to assure multiple functions in the final material. After mixing of the ternary systems, the nanocomposites are prepared by three approaches, i.e. solution casting, solution casting followed by compression molding, and freeze drying followed by compression molding. SEM analysis shows that compression molding processes lead to the highest degree of coalescence of CS15 nanoparticles. This effect is however reduced in presence of PEG or PEG/CNC. It is further observed that the presence of PEG helps protecting CNC from thermal degradation. Thermal and thermo-mechanical analyses prove a high plasticizing performance of PEG and its good confinement between the nanoparticles and at interstitial spaces. Furthermore, it is revealed that the level of material reinforcement by CNC depends strongly on the ratio between CNC and PEG due to the establishment of strong interactions via hydrogen bonding between both components, which can affect the formation of CNC percolating network. These findings allow tuning the microstructure and related properties of the nanocomposites.