Multiresponsive Polymer Hydrogels by Orthogonal Supramolecular Chain Cross Linking

Supramolecular hydrogels are water swollen networks of macromolecules interconnected by noncovalent bonds, typically established through hydrogen bonding or metal complexation. These transient cross links are susceptible to external stimulation by variation of pH, temperature, or the presence or absence competing ligands, rendering them useful for applications in soft and sensitive gelly materials. However, most existing approaches to prepare and actuate such responsive gels rely on the use of just one of these different triggers. We present an approach to overcome this limitation. We prepare multiresponsive supramolecular hydrogels based on linear polyglycerol cross linked by either hydrogen bonding, metal complexation, or both. This allows supramolecular hydrogels to be formed at mild conditions in water that remain stable for several weeks and that respond to different stimuli by partial or complete polymer de cross linking in an orthogonal fashio

Chain Dynamics in Supramolecular Polymer Networks

Supramolecular polymer networks consist of macromolecules that are cross linked by transient physical interactions such as hydrogen bonding or transition metal complexation. The utility of these networks is based on their mechanical properties, which lay between those of permanent networks and that of mechanically entangled, viscoelastic polymer solutions, depending on the strength of transient chain cross linking. To benefit from this interplay, it is necessary to understand it. To promote this understanding, we use a modular toolkit to form supramolecular polymer networks that exhibit greatly varying strength of transient chain cross linking but that are all derived from the very same precursor polymer. This strategy allows the impact of the strength of transient chain cross linking on the network dynamics and mechanics to be studied with high consistency. We follow this approach to evaluate the diffusive mobility of labeled tracer chains within these transient networks. Our results reveal that the concentration dependence of the tracer chain diffusivity is in agreement with theoretical predictions derived from the sticky reptation model by Rubinstein and Semenov, provided the chain association is stronger than a certain threshol

A modular construction kit for supramolecular polymer gels

Supramolecular polymer gels are swollen networks of macromolecules interconnected by transient, non covalent bonds; they form an extraordinarily useful class of soft, stimuli sensitive materials. To optimize the use of supramolecular polymer gels in applications, their physical and chemical properties must be understood. This understanding is ideally achieved using model systems that allow the type and strength of supramolecular chain crosslinking to be varied to a great extent without concurrent alteration of the properties of the covalent polymer backbones. We introduce a system that provides these requirements. We use linear chains of electrophilic methacryl succinimidyl MASI modified poly N isopropylacrylamide pNIPAAm . These polymers can be modified in a modular fashion by replacing their electrophilic MASI units by nucleophilic amine functionalized derivatives of custom, supramolecular crosslinkable functionalities. We follow this approach and prepare a set of pNIPAAm polymers that consist of exactly the same polymer backbone functionalized with different types of crosslinkable sidegroups. These polymers are then crosslinked by addition of low molecular weight linkers that are complementary to the motifs on the polymer. We use multiple hydrogen bonding based on diaminotriazine and maleimide, cyanuric acid and Hamilton wedges, and diaminotriazine and cyanuric acid; we also use metal complexation based on terpyridine and different metal salts. This approach creates supramolecular networks of greatly varying rheological properties, from low viscous liquids to elastic gels, each showing consistent and quantitative correlation between the gel mechanical properties and the binding strength of the respective constituent supramolecular crosslinking motifs. Exploiting the good solubility of the common pNIPAAm backbone polymer in a variety of solvents allows these networks to be prepared and studied in different media with unprecedented consistency and flexibilit

Diagnosing peri-implant disease using the tongue as a 24/7 detector

Our ability of screening broad communities for clinically asymptomatic diseases critically drives population health. Sensory chewing gums are presented targeting the tongue as 24/7 detector allowing diagnosis by “anyone, anywhere, anytime”. The chewing gum contains peptide sensors consisting of a protease cleavable linker in between a bitter substance and a microparticle. Matrix metalloproteinases in the oral cavity, as upregulated in peri-implant disease, specifically target the protease cleavable linker while chewing the gum, thereby generating bitterness for detection by the tongue. The peptide sensors prove significant success in discriminating saliva collected from patients with peri-implant disease versus clinically asymptomatic volunteers. Superior outcome is demonstrated over commercially available protease-based tests in saliva. “Anyone, anywhere, anytime” diagnostics are within reach for oral inflammation. Expanding this platform technology to other diseases in the future features this diagnostic as a massive screening tool potentially maximizing impact on population health