Strain Hardening of Highly Stretchable Elastomeric Composites Reinforced with Well-Defined Nanofiber Network of Bacterial Cellulose

Highly stretchable poly(ethyl acrylate) (PEA) composites reinforced with a well-defined nanofiber network of bacterial cellulose (BC) were prepared via stepwise solvent exchange followed by in situ photo-initiated free radical polymerization. Despite the small volume fraction of BC (approximately 0.4 vol%), the BC/ PEA composite showed significant increases in Young's modulus (26 times larger than that of the neat PEA), tensile strength (35 times larger), and fracture energy (3.8 times larger), with its fracture strain (1520 %) almost the same as that of the neat PEA (1660 N. This composite was characterized by effective strain hardening. The changes in strain-hardening modulus and tensile strength were explained well by the rule of mixtures. Confocal laser scanning microscopic observations revealed the structure of the nanofibers embedded in the elastomeric matrix. The enhanced mechanical properties were discussed based on the rigidity and flexibility of the BC nanofibers and their entangled network and were ascribed to the well-defined BC nanofiber network produced by the bacterium.