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Functionalization of lignin was carried out with 4,4′-diphenyl methane diisocyante (MDI) at 90 °C for 60 min. Formation of the resulting reaction products was confirmed with the help of FTIR, FESEM–EDAX and DSC. Polymer blends were prepared using an isocyanate prepolymer (NCO/OH: 3.5) and functionalized lignin (up to 15 wt%) and evaluated their phase miscibility, wettability, rheology and mechanical properties. Under DMA run, the maximum storage and loss moduli of blends were observed at 5 wt% lignin content. Wettability results indicated that as the lignin content increased in the blends, the contact angle of probe liquids on the substrate increased while polar component of surface-free energy decreased affecting their wettability. FTIR spectra of the blends showed disappearance of –NCO peak at 2270 cm⁻¹ supported its consumption in the network formation. Rheological test revealed that lignin …