Dilute solution properties of four natural chitin in NaOH/urea aqueous system

Four kinds of natural chitin originating from crab (C1), shrimp (C2), silkworm chrysalis (C3) and flies shell (C4) were dissolved in 8 wt.% NaOH/4 wt.% urea aqueous solution. Dilute solution behavior of chitin was examined by laser light scattering and viscometry. The Mark–Houwink equation and the relationship between the z-average radius of gyration (Rg) and the average-weight molecular (Mw) for C1 in the solvent at 25 °C were determined to be [η] = 0.26Mw0.56±0.02 (mL g−1) and Rg = 0.15Mw0.47±0.03 (nm), respectively. On the basis of the polymer solution theory, the conformation parameters of C1 to C4 samples were calculated to be in the range of 25–18 nm for the length of the Kuhn statistical segment (Qk), and 43–32 for the characteristic ratio (C∞), respectively. It indicated that chitin molecules existed in a random-coil chain conformation, and chain flexibility increases from C1 to C4 in NaOH/urea aqueous system.