Osmosis-Induced Mechanical Disintegration of Polymer Network Gels.

A polymer network soaked in its good solvent absorbs the solvent molecules to swell up. The structurally possible swelling range of a polymer network is from its dried state to the structural swelling limit where its network strands reach their stretching limit. However, swelling of a polymer network to near its structural limit has not been realized due to the thermodynamic limitation. Here, this research succeeds in excessive swelling of polymer networks to or even beyond their structural swelling limit. For the excess swelling, dense linear polymers are repeatedly introduced inside a polymer network of interest. The linear polymers, trapped inside the polymer network, generate extremely high osmotic pressure and make the polymer network swell excessively. The resulting polymer networks, overswollen beyond their structural limit, disintegrate into microgels due to catastrophic scission of the polymer network strands, analogous to osmotic hemolysis of red blood cells in a hypotonic solution. This research is expected to contribute to osmosis-induced mechanodegradation of polymer network materials and well-controlled, swelling-based mechanochemistry.