Chemically Fueled Reinforcement of Polymer Hydrogels

Carbodiimide-fueled anhydride bond formation has been used to enhance the mechanical properties of permanently crosslinked polymer networks, giving materials that exhibit gel-gel-gel transitions. Temporary changes in mechanical properties result from a transient network of anhydride crosslinks which eventually dissipate by hydrolysis. Over an order of magnitude increase in storage modulus is possible through carbodiimide fueling. The time-dependent mechanical properties could be modulated by the concentration of carbodiimide, temperature, and primary chain architecture. Because the materials remain rheological solids, applications such as temporally controlled adhesives and rewritable spatial patterns of mechanical properties are possible.