Mechanical and Thermal Properties of Porous Nanocellulose/Polymer Composites: Influence of the Polymer Chemical Structure and Porosity.

The excellent emulsifying capacity of nanocellulose allows for the preparation of porous nanocellulose/polymer composites through the emulsion templating process. However, the effects of the polymer chemical structure and porosity on the material properties have not been extensively explored. Here, we discuss the effects of these two factors on the thermal and mechanical properties of the composites. Two types of porous nanocellulose/polymer composites were fabricated with styrene-divinylbenzene (poly(St--DVB)) or styrene-poly(ethylene glycol) dimethacrylate (poly(St--EGDMA)) copolymers as the polymer phases. The porosity of the composite was changed up to ∼50% v/v by varying the aqueous phase volume fraction in the original nanocellulose-stabilized w/o emulsions. As the porosity increased, the thermal conductivity of the composite decreased. The mechanical properties were strongly influenced by the polymer type; the nanocellulose/poly(St--DVB) composite showed stiff but brittle behavior, whereas the nanocellulose/poly(St--EGDMA) composite showed higher strength and toughness. In both types of composites, the nanocelluloses served as reinforcing agents, contributing to the improvement of the mechanical properties.