Benedict Sandmann

Self-healing metallopolymers based on cadmium bis(terpyridine) complex containing polymer networks

The utilization of metal–ligand interactions within polymers generates materials which are of interest for several applications, including self-healing materials. In this work we use methacrylate copolymers containing terpyridine moieties in the side chain for the formation of self-healing metallopolymer networks. The materials were synthesized using the reversible addition–fragmentation chain transfer (RAFT) polymerization technique and subsequent crosslinking by the addition of a metal salt, here cadmium(II) salts, with different counter-ions. The influence of the counter-ions on the self-healing process within these structures was analyzed. The research resulted in a new polymeric material featuring a high (intrinsic) healing efficiency at relatively low temperatures (<75 °C).

Photoinduced polyaddition of multifunctional azides and alkynes

The photoinduced copper(I)-catalyzed polymerization of multifunctional azides and alkynes is facilitated by the photoreduction of copper(II) acetate generating copper(I) ions without using any additional photoinitiator. The polymerization can only be carried out in solution using at least 15 wt% of methanol. Depending on the catalyst concentration quantitative monomer conversions can be achieved allowing the determination of the mechanical properties. The bifunctional system consisting of a di-azide and di-alkyne exhibited the highest Youngs modulus value of 1600 MPa.

Metallopolymers as an Emerging Class of Self-Healing Materials

Metallopolymers are highly interesting materials with properties combining typical polymeric features with the properties of metal–ligand complexes. Thereby, the incorporation of different metal complexes into the polymeric material enables the tuning of the resulting material’s properties. In particular, ionic interactions between charged metal complexes and the corresponding counterions as well as reversible (switchable) metal–ligand interactions make these materials potentially interesting as self-healing materials. Compared to other self-healing polymers, the research on these materials is still in its infancy. This review summarizes the latest trends in the research regarding this class of materials.

The Self-Healing Potential of Triazole-Pyridine-Based Metallopolymers

The development of artificial self-healing materials represents an emerging and challenging field in material science. Inspired by nature-for instance by the self-healing of mussel byssus threads-metallopolymers gain more and more attention as attractive self-healing materials. These compounds are able to combine the properties of both polymers and metal-ligand interactions. A novel metallopolymer is developed consisting of attached bidentate triazole-pyridine (TRZ-py) ligands and a low glass transition temperature (T g ) lauryl methacrylate backbone. The polymer is cross-linked with different Fe(II) and Co(II) salts. The resulting materials exhibit promising self-healing performance within time intervals of 5.5 to 26.5 h at moderate temperatures of 50 to 100 °C. The materials are characterized by X-ray scattering (SAXS), UV-Vis spectroscopy, and light microscopy.

Incorporation of core–shell particles into methacrylate based composites for improvement of the mechanical properties

The fracture toughness of polymeric materials and composites can be enhanced by the incorporation of polymer nanoparticles. The combination of a soft core and a hard shell leads to an improvement of the fracture toughness of the polymeric composites. Thereby, the mechanical resistance of the materials is commonly decreased. In our approach, core–shell nanoparticles consisting of an ethylene glycol dimethacrylate (EGDMA) crosslinked poly(butyl acrylate) (PBA) core and a poly(methyl methacrylate) (PMMA) shell were synthesized. The polymer particles were incorporated into triethylene glycol dimethacrylate (TEGDMA)/urethane dimethacrylate (UDMA) based composites in order to tune the mechanical properties. Different core–shell ratios were applied to study the influence on the fracture toughness and E-modulus. An examination of shell-crosslinking with a TEGDMA content of up to 8% was performed to improve particle stability and dispersibility. The particle sizes and morphologies were characterized by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM) and analytical ultracentrifugation (AUC). Latex particle sizes of 70 to 220 nm were obtained. The mechanical properties (flexural strength, E-modulus and K1c) of polymer composites were investigated in three-point bending tests. Core/shell ratios of 50/50 showed a decreasing effect on flexural strength, E-modulus and K1c. Polymer particles with core/shell ratios of 30/70 led to a significant increase of the mechanical properties with maxima of 1.206 MPa m1/2 (K1c) (increase of 65%), E-modulus of 1.90 GPa (increase of 18%) and flexural strength of 79 MPa (increase of 18%). This study represents the first report of a simultaneous improvement of fracture toughness and E-modulus (at the same time) of additive filled polymer composites. The improvement of mechanical properties makes these materials interesting as tougheners for hard tissue applications like bone cements or dental replacement materials.