Chemically fueled transient self-assembly of polymer building blocks

Abstract: Living organisms are highly complex, hierarchically organized chemical systems with the ability to autonomously sense, adapt, evolve, or reproduce. In order to do so, they operate far from thermodynamic equilibrium, requiring the constant input and dissipation of energy. This is achieved through the metabolism of high-energy molecules like glucose. Such dissipative conditions imbue biological systems with the ability to dynamically reorganize structures over multiple length scales, resulting in a high degree of spatiotemporal control over morphology and functionality. In contrast, man-made materials form under near-equilibrium conditions, with the self-assembly of building blocks driven by energy-minimization being one of the cornerstones of modern material science. Despite tremendous progress that has led to the emergence of advanced functional materials using trigger-responsive moieties, artificial systems with truly life-like properties have remained an elusive goal. With the goal to impart the unique properties of life to synthetic systems, strategies to drive self-assembly using high-energy molecules (chemical fuels) have recently emerged at the interface between physics, chemistry, biology and material science. Within this relative young field, polymer building blocks are underrepresented, but present promising opportunities for new out-of-equilibrium materials systems.
This thesis presents the chemically fueled, transient self-assembly of poly(carboxylic acid) building blocks with three fundamentally different architectures. The use of a carbodiimide fuel generates a cyclic chemical reaction network (CRN), consisting of the formation of carboxylic anhydrides mediated by the carbodiimide as the activation reaction, and anhydride hydrolysis in the aqueous medium as the deactivation step. Self-assembly occurs as a result of the formation of hydrophobic anhydride groups from hydrophilic carboxylic acids.
A first example explores poly(methacrylic acid) microgels that undergo a transient volume phase transition (transient deswelling) in the presence of the fuel. As representatives of both polymer hydrogels and colloids, the microgels exhibit colloidal aggregation as a second fueling mode at high fuel concentrations. The transient uptake of a solvatochromic dye into the deswollen microgels highlights controlled uptake and release as a potential application. The second system is based on linear homopolymers which are of interest to find answers to more fundamental questions in chemically fueled phase transitions. Upon the addition of the fuel, dilute poly(norbornene dicarboxylic acid) (PNDAc) solutions undergo transient spinodal decomposition leading to the formation of bicontinuous polymer-rich and polymer-depleted domains. Initially domain growth is diffusive, but it eventually arrests as a result of competition between phase separation and the CRN.
Finally, block copolymers that consist of a hydrophilic block and a fuel-responsive PNDAc block serve as transient amphiphiles for chemically fueled micelle formation. Using block copolymers with different block ratios, the structural diversity of micellar aggregates is investigated

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2021

Classification and Topics

• Keyword: Building

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2022
• Creator: Heckel, Jonas
• Contributor: Walther, Andreas ; Albert-Ludwigs-Universität Freiburg. Fakultät für Chemie und Pharmazie

Further information

• DOI: 10.6094/UNIFR/223560
• URN: urn:nbn:de:bsz:25-freidok-2235607
• Rights: Kein Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:44 PM CET