Collagen is well-known for lower critical solution temperature (LCST)-like transition and gel formation where the viscosity of collagen solution increases if the temperature is raised from pH and temperature. Temperatures higher than normal physiological temperature, however, causes melting of the collagen fibrillar assembly. Hence, a 2 w% collagen furan solution has also been assessed for its capability of similar gel formation by oscillatory rheology where the complex viscosity (η*) was measured over a temperature range from 25 to 50 °C and compared with 2 w% pristine collagen solution. Both pristine collagen and collagen furan showed a slight increase in η* by increasing the temperature from 25 °C and attained the highest value at 28 °C for pristine collagen and 36 °C for collagen furan, indicating fibrillation (Figure ). Further increase in temperature resulted in decrease of complex viscosity which reached a stable value at 45 °C for both pristine collagen and collagen furan. Moreover, the loss tangent (tan δ) increased with increasing temperature indicating more damping and energy dissipation in the gel as can be expected due to the increased mobility of the individual collagen molecules within the intermolecular assembly at higher temperature. The loss tangent reached its maxima at 39 and 45 °C for pristine collagen and collagen furan, respectively, indicative of the melting of the collagen triple helix at these temperatures. A higher triple helix melting temperature could be attributed to the stabilization of the triple helix rendered by the hydrophobic furan modifications in collagen furan. It was demonstrated earlier for collagen mimetic peptides that hydrophobic modifications bestow hyperstability in polyproline II triple helix. Moreover, above the melting temperature of the polyproline II triple helix, pristine collagen solution behaved as a viscous liquid with a tan δ higher than unity whereas collagen furan still demonstrated a gel-like behavior with tan δ value residing below unity (Figure ). To our understanding, this is due to the hydrophobic associations between the furan groups on the random coil of collagen polypeptide after melting of the polyproline II triple helix. Preparation of hydrogel. To demonstrate the formation of chemically crosslinked hydrogel via cycloaddition between furan and maleimide groups, solutions of collagen furan and 8-arm PEGmaleimide in PBS were mixed together at pH 5-6. Crosslinking was qualitatively confirmed by lifting the hydrogel from the mold with a tweezer or spatula. Furthermore, the time required for complete gelation was examined at 25 and 37 °C. For this purpose, the precursors of r2 hydrogel (Supplementary Table ) were mixed together, cast onto the rheometer plate, and the storage and loss moduli were monitored over 44 hours (Figure ). As non-crosslinked collagen solution is known to behave as a gel (G´ > G´´) above 0.5% concentration at 1Hz, a typical sol-gel transition was not possible to observe for collagen furan hydrogel formation. Rather the gradual increase of storage modulus over time was considered as gelling due to covalent crosslinking, and the time required to obtain a plateau in storage modulus was considered as the time needed for complete gelation. Nonetheless, storage modulus of our developed hydrogel did not reach a plateau over 44 hours (Figure ). The rate of increase of storage modulus was slightly higher at 37 °C compared to 25 °C (Figure ) as expected since the reaction can proceed faster at a higher temperature and collagen undergoes fibrillation leading to gel formation at 37 °C. Hence, r2 hydrogels were prepared separately and kept in the mold for different duration (1, 3, and 7 days) before subjecting them to rheological amplitude sweep for determination of storage and loss moduli. As shown in Figure , storage modulus increased significantly with changing the curing time from one day to three days. In contrast, from day 3 to day 7, there was not a significant increase in the storage modulus.