The concentration dependence of the structure of fibrin gels, formed following fibrinogen activation by thrombin at a constant molar ratio, was investigated by means of elastic light scattering techniques. The scattered intensity distributions were measured in absolute units over a wave-vector range q of about three decades $(\sim 3\times {10}^2–3\times {10}^5{\mathrm{cm}}^{-1}).\mathrm{}$ A set of gel-characterizing parameters were recovered by accurately fitting the data with a single function recently developed by us [F. Ferri et al., Phys. Rev. E 63, 031401 (2001)], based on a simple structural model. Accordingly, the gels can be described as random networks of fibers of average diameter d and density ρ, entangled together to form densely packed and spatially correlated blobs of mass fractal dimension $D_m$ and average size (or crossover length) ξ. As previously done for d, we show here that the recovered ξ is also a good approximation of a weight average, namely, $d\sim \sqrt{〈d^2{〉}_w}$ and $\xi \sim 〈\xi {〉}_w.$ By varying the fibrinogen concentration $c_F$ between 0.034–0.81 mg/ml, gels with $100>~\xi >~10\mu \mathrm{m},$ $100<~d<~200\mathrm{nm},$ $1.2<~D_m<~1.4,$ and constant $\rho \sim 0.4\mathrm{mg}/\mathrm{ml}$ were obtained. The power-law $c_F$ dependencies that we found for both ξ and d are consistent with the model, provided that the blobs are allowed to partially overlap by a factor η likewise scaling with $c_F$ $(2\mathrm{}>~\eta >~1).$ Recasting the whole dataset on a single master curve provided further evidence of the similarity between the structures of all the gels, and confirmed the self-consistency of the model.

• Received 14 January 2002

DOI:https://doi.org/10.1103/PhysRevE.66.011913