Site-specific reactions of softwood kraft lignin for biobased vitrimers and reactive colloidal particles

Lignin, a natural polyphenolic compound of wood, holds promise as a green alternative to fossil resources given the current environmental concerns. However, its complex structure and limited usability have impeded widespread use of lignin in biobased materials. This thesis is focused on employing a series of chemistries and techniques that facilitate lignin utilization in a variety of applications ranging from bulk materials to colloidal particles. Lignin-based vitrimers, developed by a one pot, catalyst-free click addition of poly(ethylene glycol) divinyl ether to softwood kraft lignin and formation of dynamic acetal exchange network showed excellent performance as recoverable adhesives, reaching lab shear strengths of 2.6 MPa and 6.0 MPa for wood and aluminum substrates, respectively. Stabilized lignin nanoparticles synthesized by hydrothermal crosslinking of hydroxymethylated lignin nanoparticles showed an excellent colloidal stability in organic solvents such as ethanol, acetone, dimethylformamide, and tetrahydrofuran, and aqueous media (3 < pH < 12). These stabilized lignin nanoparticles were subjected to direct surface modification in colloidal state to develop aminated pH-responsive particles. Stabilized lignin nanoparticles, preserving redox activity, showed a capacity in reducing silver ions, forming hybrid lignin-silver nanoparticles for applications such as hydrogen peroxide colloidal sensors. Interaction of silver ions and stabilized lignin nanoparticles contributed to the emergence of discrete patterns of silver in lignin nanoparticle embedded hydrogels. The location and distance of the discrete patterns can be modified by altering the particle size and concentration. Furthermore, redox activity of stabilized lignin nanoparticles, hydroxymethylated lignin nanoparticles and unmodified lignin nanoparticles with different particle sizes (90 nm, 150 nm, 640 nm) were studied in charge storage applications in organic poly(3,4-ethylenedioxythiophene) pol