Synthesis and characterization of multiarm star-shaped water-soluble graft copolymer through atom transfer radical polymerization of acrylamide initiated from bio-based lignin macroinitiator

In this research, two types of lignin-based macroinitiators were prepared using α-bromoisobutyrylation reaction. Hydroxyl groups (OH) of lignin were completely or partially α-bromoisobutyrylated to produce two types of macroinitiators. Lignin-g-polyacrylamide graft copolymers soluble in water over the full range of pH were synthesized by atom transfer radical polymerization (ATRP) of acrylamide initiated from bio-based lignin macroinitiator. Progress of all reactions and synthesis of multiarm star-shaped graft copolymers were evaluated with the help of Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (1HNMR). Depending on the macroinitiator type and reaction condition, the semi-empirical molecular weights of the synthesized copolymers were estimated to be between 19,705 and 52,412 g/mol, and the molecular weights of the arms were in the range of 4919–7821 g/mol. Thermal behavior of the samples was also investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).