Dorcas Ovurevu - PhD defense

Carbohydrate-based block copolymers (CBCPs) combine the renewability and functionality of carbohydrates with synthetic polymer architectures, yet their potential as intrinsically self-healing materials remains underexplored.

Herein, a bio-based, multifunctional CBCP is developed that integrates hierarchical self-assembly in both aqueous solution and the bulk state with moisture-responsive, reiterative self-healing under ambient conditions.

Linear triblock architectures were synthesized via azide–alkyne click chemistry using hydroxyl-rich malto-oligosaccharide as end blocks and mid-blocks such as polybutadiene (PB) or polydimethylsiloxane (PDMS).

In aqueous media, the CBCPs self-assembled into nanoparticles that evolved from spherical micelles to rods and vesicular structures. In the as-cast bulk state, the materials displayed microphase separation dominated by a lamellar morphology.

Tensile testing, particularly of PB-containing CBCP, showed a modulus of ~67 MPa and tensile strength of ~3.6 MPa, with measurable energy dissipation during deformation. Fractured specimens restored up to ~98% of tensile strength within 2 days, following moistening and rejoining at ambient conditions. Previously strained pristine samples, when rejoined, demonstrated reiterative healing with recovery of modulus and strength across cycles.

Small-Angle X-ray Scattering (SAXS) data upon water exposure revealed expansion of saccharide-rich domains while preserving structural order, supporting a mechanism of moisture-assisted domain rearrangement. The CBCPs further retained mechanical performance after reprocessing, indicating recyclability.

The concept was extended to fully biobased CBCPs, prepared via ring-opening polymerization (ROP) of decalactone, followed by coupling reactions. The resulting systems likewise exhibited effective self-healing behavior.

These findings highlight the versatility of saccharide-driven supramolecular interactions in enabling moisture-responsive healing and thereby contribute to ongoing efforts to design and develop functional bio-based polymer systems for several potential applications.

Membres du Jury :

Takuya Isono, Professeur, Université de Hokkaido (Rapporteur)
Delphine Chan-Seng, Chargée de recherche CNRS – Alsace (Rapporteure)
François Tournilhac, Directeur de recherche CNRS – Paris (Examinateur)
Sabine Rolland-Du-Roscoat, Professeure des Universités, UGA (Examinatrice)
Nadia El-Kissi, Directrice de recherche CNRS – Alpes (Co-directrice de thèse)
Redouane Borsali, Directeur de recherche CNRS – Alpes (Directeur de thèse)