Carbodiimide-fueled anhydride bond formation has been used to enhance the mechanical properties of permanently crosslinked polymer networks, giving materials that exhibit transitions from soft gels to covalently reinforced gels, eventually returning to the original soft gels. 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 the storage modulus is possible through carbodiimide fueling. The time-dependent mechanical properties can be modulated by the concentration of carbodiimide, temperature, and primary chain architecture. Because the materials remain rheological solids, new material functions such as temporally controlled adhesion and rewritable spatial patterns of mechanical properties have been realized.

The mechanical properties of nonequilibrium polymer hydrogels obtained from the transient cross-linking of polymer chains by a chemical fuel were investigated. Aqueous polymers featuring pendant carboxylic acids were treated with a carbodiimide to give anhydride-cross-linked gels. The anhydrides spontaneously hydrolyze back to the polymer solution, and the cycle can be repeated multiple times. Oscillatory rheology was employed to study the effects of temperature, fuel concentration, chain length, and polymer composition on the storage and loss moduli of the polymeric materials as well as the time taken for the polymers to undergo decross-linking. Regardless of the temperature used, at constant carbodiimide concentration, degelation times are more sensitive to experimental temperature than are the peak storage moduli. Decross-linking times decrease with increasing temperature. As carbodiimide concentration decreases, there is a decrease in moduli and decross-linking times. Within the scope of materials studied, the polymer structure was found to have a relatively small impact on the transient properties of gel networks compared to the fuel concentration and temperature. These findings facilitate the design of tunable on-demand networks and gels.

Coronavirus disease 2019 (COVID-19) has significantly impacted human health, the global economy, and society. Viruses residing on common surfaces represent a potential source of contamination for the general population. Spike binding peptide 1, SBP1 is a 23 amino acid peptide, which has micromolar binding affinity (1.3 μM) towards the spike protein receptor-binding domain. We hypothesize that if we can covalently immobilize this SBP1 peptide in a covalent crosslinked network system, we can develop a surface that would preferentially bind spike protein and, therefore, which could limit viral spread. A series of covalently crosslinked networks of hydroxy ethyl acrylate (HEA) with different primary chain lengths and crosslinker density was prepared. Later, this network system was functionalized using 2% SBP1 peptide. Our study found that with a shorter chain length and lower crosslinker density, the HEA network system alone could capture almost 80% of the spike protein. We reported that the efficiency could be enhanced almost by 17% with higher crosslinker density.

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.