Tunable biohybrid hydrogels from coacervation of hyaluronic acid and PEO-based block copolymers

Accurately tuning the macroscopic properties of biopolymer-based hydrogels remains challenging due to the ill-defined molecular architecture of the natural building blocks. Here, we report a biohybrid coacervate hydrogel, combining the biocompatibility and biodegradability of naturally occurring hyaluronic acid (HA) with the tunability of a synthetic polyethylene oxide (PEO) -based ABA-triblock copolymer. Coacervation of the cationic ammonium or guanidinium-functionalized copolymer A-blocks with the anionic HA leads to hydrogel formation. Both mechanical properties and water content of the self-healing hydrogels can be controlled independently by altering the copolymer structure. By controlling the strength of the interaction between the polymer network and small-molecule cargo, both release rate and maximum release are controlled. Finally, we show that coacervation of HA and the triblock copolymer leads to increased biostability upon exposure to hyaluronidase. We envision that noncovalent crosslinking of HA hydrogels through coacervation is an attractive strategy for the facile synthesis of tunable hydrogels for biomedical applications.     

Helical bias in supramolecular polymers accounts for different stabilities of kinetically trapped states

The idea to synthesize and self-assemble nano-graphenes with structural precision into supramolecular polymers is just one of Klaus Müllen's many pioneering contributions to the chemical sciences. To honor his impact in the field of polymer science, we here describe a study that combines experimental and computational methods in studying the stability of kinetically trapped states of supramolecular polymers. We show that the introduction of stereocenters in the sidechains allow helical supramolecular polymers based on chiral triphenylene-2,6,10-tricarboxamide monomers to escape a kinetic trap more efficiently than polymers based on their achiral analogs. Partial depolymerization of the kinetically trapped state by increasing the temperature followed by polymerization by lowering the temperature shows that monomers either polymerize on existing stacks or self-nucleate to form the thermodynamically more stable state. Chiral monomers prefer the latter more than achiral monomers.     

Controlling the gelation temperature of biomimetic polyisocyanides

The gelation temperature and mechanical properties of aqueous ethylene glycol-decorated polyisocyanide solutions strongly depends on the length of the glycol tail. Copolymerisation of monomers with different tail lengths allows for precise engineering of the gel properties.     

Temperature-dependent modulation by biaryl-based monomers of the chain length and morphology of biphenyl-based supramolecular polymers

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials. Yet, general principles and structure–property relationships for rational comonomer design remain lacking. Here, we report on the supramolecular (co)aggregation of a phenylpyridine and bipyridine derivative of a recently reported biphenyl tetracarboxamide-based monomer. We show that both arylpyridines are poor monomers for supramolecular homopolymerizations. However, the two arylpyridines efficiently influence supramolecular polymers of a biphenyl-based polymer. The phenylpyridine derivatives primarily sequestrate biphenyl monomers, while the bipyridine intercalates into the polymers at high temperatures. Thereby, these two poorly homopolymerizing monomers allow for a fine control over the length of the biphenyl-based supramolecular polymers. As such, our results highlight the potential to control the structure and morphology of supramolecular polymers by tailoring the electronic properties of additives.

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials.