Exploring Lignin-Based AB-Type Monomers Toward Sustainable Polyesters : Taking STEPs Toward Sustainable Plastics
Year: 2026
Type: dissertation
Abstract: More than 98% of global plastics are currently derived from fossil resources. Among these, aromatic polyesters such as polyethylene terephthalate (PET) pose severe environmental challenges, driving high greenhouse gas emissions and persistent global waste accumulation. Transitioning toward a sustainable plastics economy requires decoupling polymer production from traditional petroleum feedstocks in favor of renewable biomass. Accordingly, this thesis explores the design and synthesis of novel bio-based plastics utilizing lignin-derived aromatic molecules. By leveraging the inherent asymmetry of these lignin-based building blocks, a series of AB-type aromatic monomers and their corresponding polyesters were developed. These synthesized materials are capable of matching the performance of conventional plastics across a wide range of applications, from adhesives and thin films to rigid plastics. Crucially, this structural design balances robust material performance with integrated end-of-life pathways. The thesis employs a strategic molecular design approach to integrate predetermined end-of-life pathways directly into the polymer architecture. In the first project (Paper I), homovanillic acid, a potentially lignin-based aromatic building block, was targeted for the synthesis of sustainable homo- and copolyesters. The stoichiometric balance of this polycondensation was investigated by the addition of a small quantity of a dicarboxylate AA-type monomer into the AB-type polycondensation system, which significantly enhanced the molecular weight of the resulting polyester. In addition, copolymerization of the homovanillic-based monomer with another lignin-based AB monomer yielded a novel series of rigid polyesters, exhibiting thermomechanical properties comparable to PBT. In the second project (Paper II), a “transient-comonomer” strategy was developed to improve the efficiency of AB-type melt polycondensation. Through careful selection and optimization of the comonomer’s ratio, the intrinsic viscosity of the AB-type polyester reached 1.15 dL g-1, which is similar to that of bottle-grade PET. In Papers III and IV, three series of aromatic-aliphatic polyesters were synthesized from AB-type lignin-based monomers, derived from vanillic acid (Paper III), 4-hydroxybenzoic acid (Paper III), and syringic acid (Paper IV). The varying number of methoxy substituents in the aromatic ring of these molecules significantly affected the thermomechanical properties of the resulting copolyesters, targeting different applications. With zero or one methoxy substituent (Paper III), the copolyesters exhibited excellent film formability and enhanced barrier properties, specifically targeting food packaging applications. With two methoxy substituents, the copolyesters demonstrated decent adhesion properties to paper and metal substrates, thereby making them suitable for hot-melt adhesive applications. Furthermore, end-of-life pathways were evaluated in both papers, specifically assessing biodegradability and enzymatic depolymerization, respectively. In the final project (Paper V), a new design for multifunctional AB-type monomers derived from vanillin and syringaldehyde via aldol condensation was explored. These monomers are endowed with enone groups, enabling post-polymerization modifications with different chemistryKey words: polyester, polycondensation, aromatics, bio-based, sustainable plastic
Author: Nguyen, Tam
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221264054