Small-angle neutron scattering study on irradiated kappa carrageenan

The structure of gamma-ray-irradiated κ-carrageenan in aqueous solutions was investigated in terms of small-angle neutron scattering. The scattered intensity, I(q), of non-irradiated κ-carrageenan solutions (5 wt%) was well described with an Ornstein-Zernike (OZ)-type function with the correlation length of 85 Å, indicating that the κ-carrageenan solution behaves just as a polymer solution in the semi-dilute regime. By increasing the irradiation dose (100 kGy), I(q) changed to a power-law function with the scattering exponent of −1.84. Further increase in dose results in a recovery of OZ-type function. This indicates that a progressive cleavage of κ-carrageenan chains takes place randomly, leading to a self-similar structure at 100 kGy. This is followed by further segmentation of κ-carrageenan chains.