On the strain stiffening and nanofiber orientation of physically crosslinked nanocellulose hydrogels

•Effects of micro/nanostructures on the strain stiffening behaviors of hydrogels.•Helmholtz free energy capturing the potential energy of physical crosslink.•Fiber orientation model correlating nanofiber orientation with mechanical stretch.•Evolution of nanofiber orientation in nanocellulose hydrogels under stretching.