Tuning topology towards stronger and tougher polymers inspired by semi-crystalline cellulose nanofibrils

A long-standing challenge in material design is to overcome the conflict between strength and toughness, which generally contradict each other. Natural cellulose-enabled advanced materials are promising solutions due to their remarkable capabilities to increase toughness without sacrificing strength. Nevertheless, the lack of mechanistic understanding on their elementary building block, the semi-crystalline cellulose nanofibril, hinders the understanding and designing of stronger and tougher advanced polymeric materials where hydrogen bonds and chain topologies play critical roles. In this study, we address above challenges starting from molecular simulations of semi-crystalline cellulose nanofibrils. It is found that the strength and toughness of cellulose nanofibrils can simultaneously increase by tuning the semi-crystalline topologies, leading to simple topology engineering strategies to design ultra-strong and ultra-tough nanofibril and network structures. The fundamental mechanisms and designing concepts can be readily extended into material systems where secondary bonds are important, enabling a wide range of strong and tough advanced polymeric materials.