Dynamic shear rheology study is conducted on the polyacrylonitirile (PAN) solution and composite solutions of PAN with up to 37.5 wt% annual plant lignin (APL) to address current barriers of PAN/lignin blend development as carbon fiber precursor. PAN/APL blends exhibit lower yield stresses, lower relaxation times, and lower viscosities than to PAN solution according to the dynamic frequency sweep measurements from -7 degrees C to 56 degrees C. Yet an increase of solution activation energy of flow is observed with the increasing lignin content in solution. This is attributed to the potential interactions of PAN and lignin. Solution loss tangents obtained from dynamic frequency sweeps between -7 degrees C and 56 degrees C at an oscillatory frequency of 100 rad/s is used to envision the effect of lignin on solution structure during fiber processing. (c)2017 Elsevier Ltd. All rights reserved.