Dear Readers,

You might have notice that “Image of the Day” was missing from last week’s newsletter.

I’ve been on the lookout for aesthetic journal covers but it has become less common to view these in the digital world. You might recall looking for papers on Google Scholar where the link click leads you directly to the paper.

Therefore, IOTD will not be a regular segment in future newsletters. I’ll attach one only if I come across an interesting cover.

In The News

Research Updates

Programming Hydrogel Adhesion With Engineered Polymer Network Topology (Link)

• The authors report a new strategy to program hydrogel adhesion by engineering the surface network topology of the hydrogel, which creates different types of polymer entanglements (linkages) at the interface.

• These linkages can be classified into three types: slip, stitch, and hybrid, depending on the ratio of the penetration depth of the bridging polymer to the thickness of the dangling chain layer on the hydrogel surface.

• The slip linkage exhibits dynamic and rate-dependent adhesion, similar to the slip bonds in cell adhesion, while the stitch linkage shows high and rate-independent adhesion, similar to the covalent bonds in synthetic adhesives. The hybrid linkage combines the features of both slip and stitch linkages.

• The adhesion energy, kinetics, and spatial distribution can be programmed by tuning the type and number of linkages, which are controlled by the cross-linker density and the hydrophobicity of the mold used to form the hydrogel.

• The authors demonstrate the universal applicability of the strategy to various material systems, such as single-network and double-network hydrogels, and various bridging polymers and targeted substrates.

• Potential applications include the fabrication of soft devices like smart wound patches, fluidic channels, drug-eluting devices, and reconfigurable soft robotics.

Fast Recovery Double-Network Hydrogels Based on Particulate Macro-RAFT Agents (Link)

• The authors prepared a double-network (DN) hydrogel with high strength, toughness, and recoverability using carboxyl-substituted polystyrene (CPS) and polyacrylamide (PAAm).

• CPS forms a rigid and brittle first network with four-armed amino-terminated polyethylene glycol (4-armed-PEG-NH2) by covalent cross-linking, and the PAAm forms a loose and ductile second network by photopolymerization.

• CPS chains collapse into nanospheres in water due to hydrophobic interactions, but they can be elongated under external force and restore their original shape when the force is removed.

• The DN hydrogel exhibits exceptional mechanical properties, such as 0.62 kJ m⁻² fracture energy, 2510.89 kJ m⁻³ toughness, 0.43 MPa strength, and 820% elongation. It also displays superior recoverability (94.5%) after cyclic loading.

• This work demonstrates the novel design of a fully chemical DN hydrogel with recoverability and provides a wider platform for the application of hydrophobic polymers.

Share This Newsletter

Thank you for reading this edition of the Hydrogels newsletter!

If you enjoyed reading this newsletter, share the word with your friends by asking them to visit this link: