PhD Defence Suna Azhdari | Degradable Block Copolymers: From Molecular Design to Functional Nanocarriers for Agrochemical Delivery

Degradable Block Copolymers: From Molecular Design to Functional Nanocarriers for Agrochemical Delivery

Suna Azhdari is a PhD student in the Department of Sustainable Polymer Chemistry. Promotors are prof.dr. F.R. Wurm from the Faculty of Science & Technology (UT) and prof. A.H.G. Gröschel from the University of Münster.

Sustainable Polymer ChemistryThis dissertation investigates the development, structural control, and application of copolymers and their self-assembly behaviour, with a focus on potential uses in sustainable agriculture and biomedical applications. The conditions under which complex nanostructures can form are analysed, and structure property relationships are explored. Building on this, materials are designed through tailored molecular structures and controlled self-assembly that aim to combine high functionality with degradation, offering potential contributions to reducing microplastic pollution. The introductory chapter (Chapter 1) discusses water-soluble polymers in block copolymers, in which challenges associated with their degradation are highlighted, and places them in the context of current research.

Chapter 2 focuses on the synthesis and self-assembly of fully degradable amphiphilic polyphosphoester (PPE) gradient and block copolymers via a one-pot ring-opening polymerization. It is demonstrated how gradient strength influences morphology in aqueous media, yielding structures ranging from cylindrical micelles to polymersomes. Controlled hydrolysis of the polymersomes enables targeted release of encapsulated cargo, underlining their potential for drug delivery applications.

Chapter 3 presents a self-assembly strategy for fully degradable, porous polymer cubosomes based on PEEP-b-PLA block copolymers. The Cubosomes exhibit a highly ordered cubic Pmm channel structure with open pores and can be loaded with hydrophobic fungicides during self-assembly. A morphology transition from polymersomes to cubosomes upon cargo addition is demonstrated, accompanied by increased porosity and improved release kinetics. The fungicide-loaded cubosomes show high leaf adhesion even after simulated rainfall and undergo complete hydrolysis into environmentally benign products.

Chapter 4 applies the concept of surfactant-guided self-assembly to PEEP-b-PLA block copolymers for the formation of anisotropic nanostructures. By tuning the packing parameter, high-aspect-ratio rod-shaped carriers are obtained, featuring high fungicide loading, rapid release, and high leaf adhesion. The PEEP-b-PLA carriers degrade significantly faster in soil compared to PLA, exhibit no phytotoxicity, and maintain high antifungal efficacy.

Overall, this work demonstrates how precise control over molecular architecture and self-assembly conditions enables the tailoring of both form and function of nanocarriers, from fundamental insights to application-oriented design. The presented strategies allow the preparation of fully degradable, anisotropic, and porous particles, offering new opportunities for sustainable agriculture and biomedical applications.