The shear viscosity of aqueous collagen solutions was experimentally investigated over the temperature range of 303–353 K and collagen concentrations of 1–7 wt. %. A structural phase transition was observed at ∼315 K, corresponding to the onset of protofibril formation. It is shown that below this temperature, protofibrils containing both ordered and disordered segments are formed, with the proportion of ordered segments increasing as the temperature decreases, reaching ∼30% at 303 K. An analysis of the temperature dependence of the order parameter for the structural transition in the water–collagen system suggests that this transition exhibits characteristics of a second-order phase transition.
