Study on the structure characterisation and swelling properties of the CMSM.

In order to further understand the potential applications of cellulose membrane materials in adsorption, drug delivery, and biomedical applications, to optimise their material properties, improve their performance, and expand their application fields, carboxymethyl Salix powder (CMS) was prepared by etherification reaction using Salix powder (SPP) as the raw material. Carboxymethyl Salix powder membrane (CMSM) was subsequently prepared through wet spinning technology. The swelling properties of CMSM were investigated. The results showed that the swelling degree reached the maximum at 45 min, pH 5, temperature of 65°C, and a NaCl concentration of 0.04 mol/L, reaching 7.95 g/g. Through model fitting, it was found that CMSM fits well with the Fickian diffusion model in the early stage, while the entire swelling process fits well with the Schott model. Characterisation results indicate that the structure of CMSM is loose, porous, and uneven on the surface. This structure facilitates the diffusion of water molecules and enhances the water absorption performance of CMSM. The structure of CMSM is similar to the disordered structure of glass or plastic, presenting an amorphous structure. Additionally, CMSM exhibits good thermal stability. By regulating the swelling behaviour of CMSM, this study can develop innovative membrane materials with environmental responsiveness and multifunctionality, promoting the application of green and sustainable materials and providing theoretical support for the design of new composite membranes.