Fractal water structures affected by softener agent in cotton cloths

Broadband dielectric spectroscopy (BDS) measurements were performed on cotton cloth samples with softener agents in natural environments, and a recent analytical technique of fractal analysis refined in dielectric spectroscopy was used for water structures. Three relaxation processes observed in the GHz, MHz, and kHz regions were attributed to the dynamic behaviors of hydrogen-bonding networks (HBNs) of water and interacting molecules, hydrated polymer chains, and ions restricted in the interfaces of large structures. Fractal analysis of the GHz region suggested that the GHz frequency process was retained, even in the dry state, revealing a broad spatial distribution of HBN fragments of various sizes. This typical tendency for heterogeneous hydration in cotton cloth was emphasized by the addition of a softener agent, as the value of Cole–Cole’s relaxation time distribution parameter changed from 0.55 to 0.41. The addition of the softener agent still retained the GHz frequency process, even in the dry state. This result means that the softener inhibited the formation of hydration sites on the cellulose surface and induced the dispersion of hydration sites. Thus, HBNs are fragmented by the softener agent. On the other hand, water molecules still aggregate to retain HBNs in a restricted area. The heterogeneous dispersion of HBN fragments broadens the GHz relaxation process, and the lower-frequency tail overlaps with the lower relaxation process because of chain dynamics with interacting water molecules. The structure formed by these water molecules, which is restricted by polymer chains and related to the stiffening effect of cotton fabric, is also heterogeneously hindered by the appropriate concentration of the softening agent. These indications were also consistent with the T 2 relaxation time obtained using the Carr–Purcell–Meiboom–Gill method of nuclear magnetic resonance measurements and are consequently reflected in the hydration model for macroscopic properties of cotton fabric. Graphical abstract