Viscosity Analysis of Electron-Beam Degraded Gellan in Dilute Aqueous Solution

This study explores the effect of E-beam radiation on gellan conformations in dilute aqueous solutions. Native and E-beam-modified gellan samples (N&EBMs) were prepared at 0.05 g/cm³ in 0.1M KCl under atmospheric conditions. Their relative viscosities were measured at different temperatures, and intrinsic viscosity and molar mass were determined using the Solomon–Ciuta and Mark-Houwink equations. The degradation of molar mass was analyzed, and first-order rate constants and degradation lifetimes were calculated. Structural properties such as the radius of gyration and second virial coefficient were evaluated, yielding scaling coefficients of 0.62 and 0.15, respectively, indicating that gellan chains adopt a perturbed coil structure in a good solvent. The shape parameter confirmed that E-beam radiation did not affect the ideal random coil structure of gellan. Chain flexibility was assessed using theoretical models, including the transition state theory (TST), freely rotating chain (FRC) model, and worm-like chain (WLC) model. According to TST, E-beam radiation reduced molar mass and activation energy while increasing activation entropy, decreasing chain flexibility but enhancing solvent quality. FRC model provided the end-to-end distance (R_θ) and characteristic ratio (C_∞), while WLC model determined the persistence length (l_p). E-beam radiation decreased R_θ and increased〖 l〗_p, suggesting reduced flexibility and improved solvent interactions. However, C_∞ remained largely unchanged, indicating that gellan retained its ideal chain structure despite radiation exposure. These findings offer insight into the structural and conformational changes in gellan under E-beam radiation, with implications for its rheological and functional properties.