In situ nanofibrillar composite fiber: A model system for understanding the structural evolution of crosslinked nanofibrils

Abstract In situ formed nanofibrils, which are formed from the deformation of dispersed phase polymer during the shearing/stretching process, offer exciting opportunities for large scale manufacture of materials with high strength and toughness. However, how the topological structure, especially crosslinking network structure of dispersed phase polymer, affects the structural evolution of nano/microfibrils is remaining unclear. Here, the nanofibrillar morphology of nanofibrillar composite fibers is manipulated via controlling the crosslinking network structure of dispersed phase. By changing the length of crosslinker and mol ratio of crosslinkers, the diameter of nanofibrils can be controlled. The rheological property of the crosslinked microspheres and corresponding morphology of in situ formed nanofibrils confirm that the inhomogeneous crosslinking network shows lower storage modulus and consistency coefficient, leading to higher deformation adaptability of crosslinking network and smaller diameter of the nanofibrils. The distribution of nanofibrils along the axial direction of composite fiber greatly improved the tensile strength and toughness of composite fiber to 74 MPa and 719 MJ/m 3 , which are 45% and 180% increasement compared with the counterpart pure PMMA fiber. The findings in current study provide a new strategy to control the nanofibrillar morphology by increasing the heterogeneity of crosslinking network structure of the dispersed phase polymer.