Lignin is the second most abundant biomass material. However, utilization of lignin as a feedstock for value added materials remains very limited. This is because of its natural hyper-branched oxygenated structures and characteristics associated with such structures e.g., high rigidity of the macromolecules, low thermal stability and poor processability either in melt or solution. This is the main hurdle for engineering a polymeric product from lignin. In this study, we characterized different lignins and further developed different kinds of functional composite materials. We determined the chemistry of selected lignins having reactive linkages and rich hydroxyl groups for chemical and physical cross-linking. Significant improvement of the mechanical properties and processability with high lignin content in our new composite materials (up to above 40 wt%) opens a new door for automotive and building applications. Intriguingly, formation of the crosslinked networks and tunability of the glass transition temperatures of a rubber – lignin composite were employed to control the shape memory effects of the materials. We made programmable and tunable electrically conducting skins for stress/ strain sensing applications. We discovered that the stored elastic work for shape recovery and fixity of the composites can be tuned by thermal annealing the rubber – lignin composites. Thermally activated lignin linkages generated free radicals for macromolecular rearrangement and strong cross-linked structure formation. In this research, the hydroxyl groups of lignins were also cross-linked with functional chain-end capped-polyethylene oxide to make self-healing electrical conducting materials for human motion detection.

Finding value of lignin through chemical and physical cross-linking for versatile applications

255th National Meeting (2018)

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