Experimental and Modeling Assessment on the Rheological Behavior of Collagen Solutions Modified by Dibenzaldehyde-Terminated Polyethylene Glycol with Different Molecular Weights

A high-density rigid covalent network constructed by chemical cross-linking enhances the structural stability of collagen-based biomaterials, but inherent fragility persists due to insufficient energy dissipation. Inspired by the pangolins’ protective barrier, a dibenzaldehyde-terminated polyethylene glycol (DT-PEG) flexible cross-linker was designed in this study. The “rigid-flexible” structure, formed by flexible PEG chains and rigid covalent bonds, enabled the simultaneous optimization of structural stability and energy dissipation capabilities within the network. This dual enhancement approach can profoundly optimize the physicochemical characteristics of collagen-based biomaterials, a phenomenon fundamentally governed by the aggregation behavior of collagen molecules. Such structural evolution of collagen aggregates in solution was quantitatively captured through rheological analysis, allowing real-time monitoring of viscoelastic transitions. Steady shear measurements revealed shear-thinning behavior across all collagen solutions. As the molecular weight of DT-PEG increased, the shear viscosity of the collagen solution at 0.1 s–1 increased from 6.59 to 12.1 Pa·s. This molecular weight-dependent rheological evolution was attributed to synergistic covalent-physical interactions causing collagen aggregates to form denser networks. Synchronous increases in elastic modulus, viscous modulus, thixotropy, and creep-recovery rate provided further evidence. Both dynamic and static denaturation temperatures increased with DT-PEG molecular weight, suggesting that covalent and hydrogen bonding strengthens the stability of the triple-helical structure of the collagen molecules. Finally, all experimental data were fitted using appropriate mathematical models. The coordinated molecular-scale interactions establish quantitative structure–property relationships that can guide the design of collagen-based biomaterials with tailored viscoelastic profiles.