Strength, barrier properties, and sustainability are the ideal expectations of packaging plastics. However, packaging materials such as LDPE constitute significant environmental pollution because they are not biodegradable. Using biodegradable biopolymers renowned for their strength and barrier properties is investigated as an option to satisfy the requirements. Utilizing the strength of cellulose, glucose molecules linked by the β-1,4-glycosidic bonds, and the barrier properties of lignin, nature’s reserve of aromatic structures. Bioplastics are fabricated using an ionic liquid/cosolvent system. Using experimental and computational methods, fundamental mechanistic insights about how cellulose and lignin interact in the ionic liquid-cosolvent system (blending dynamics), the impact of lignin structure from diverse sources on performance (structure-property-performance relationship), and how the bioplastics degrade (end of life assessment) were addressed. Blending dynamics quantified the strength and abundance of hydrogen bonding, hyperconjugation, and Flory-Huggins interaction parameters between cellulose and lignin. Furthermore, increasing lignin concentration leads to a waveform pattern in viscosity due to crosslinking and plasticizing effects, and self-interaction of the IL/cosolvents is stronger than their cross-interaction. The structures of lignin across grasses, hardwood, softwood, and industrial pulping processes were correlated with the optical, antioxidant, and water vapor transmission rates and mechanical and thermal properties of cellulose-lignin bioplastics. Grassy lignin increased the elongation at break(%). Water vapor transmission rates (WVTR) depend on lignin monomers' total polar surface area (tPSA), which drives the affinity for water vapor. Antioxidant properties depend on an interplay between pKa and bond dissociation energy (BDE) of monomer’s phenolic hydroxyl groups. Lastly, the biodegradation of bioplastics follows exponential decay. Bioplastics thermal degradation follows shrinking cylinder & first-order kinetics, while LDPE follows shrinking sphere & zero-order kinetics. These results show that fundamental chemical engineering principles can be applied to complex materials while creating valuable products that address environmental needs.
