Degree

Doctor of Philosophy (PhD)

Department

Biological Engineering

Document Type

Dissertation

Abstract

Lignin (LN) is one of the most abundant polymers in nature, but it is usually considered a waste byproduct of the pulping industry. The goal of this work was to engineer sustainable materials from lignin-grafted polymers, in the form of nanoparticles and films. Lignin nanoparticles (LNPs) were developed as a delivery system for methoxyfenozide (MFZ) to facilitate translocation of the nonsystemic, hydrophobic pesticide, from roots to the leaves of soybean plants, where it targets the soybean looper—a common soybean pest. Translocation of the nanodelivered MFZ was significantly enhanced, as supported by MFZ concentrations of 1.72 μ g/g in the leaves compared to 0.39 μ g/g for the control, free MFZ. Next, amphiphilic co-polymer films were produced from alkaline lignin, and sodium lignosulfonate grafted with poly(lactic-co-glycolic) acid (PLGA) at two ratios LN:PLGA (1:4, and 1:6 w/w) using an interphase formation technique. Films presented two sides with different surface properties, as measured by contact angle and roughness. Mechanical properties of the films were also affected by the lignin type and lignin: PLGA ratio. The stability of the same type of films was tested by storing them at two different relative humidities: 30 and 70% over a period of 12 months. Results showed that lignin-grafted films maintained their roughness, contact angle, and UV shielding properties consistent over the 12-month period and maintained their mechanical integrity compared to the neat polymer films. Next, lignin was grafted with three different polyesters, PCL, PLGA, and PLA, for the development of packaging films. Lignin grafting had little effect on the mechanical and functional properties of the films while increasing significantly their UV-absorption, of importance for packaging UV sensitive products. These studies clearly show that lignin NPs were effective as nano delivery systems for hydrophobic agrochemicals, and films produced from lignin-grafted polymers showed suitable mechanical characteristics, increased UV-absorption, and stability at multiple relative humidity conditions. This demonstrates that lignin is a versatile polymer to be employed in the development of biomaterials for agrochemical and packaging applications.

Date

10-30-2025

Committee Chair

Sabliov, Cristina M.

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