Probing the degree of crosslinking of a cellulose based superabsorbing hydrogel through traditional and NMR techniques

• Published in: Polymer (Guilford) Vol. 44; no. 5; pp. 1577 - 1588
• Main Authors: Lenzi, F., Sannino, A., Borriello, A., Porro, F., Capitani, D., Mensitieri, G.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2003; Elsevier
• Subjects: Applied sciences; Cellulose; Cellulose and derivatives; Degree of crosslinking; Exact sciences and technology; Natural polymers; Physicochemistry of polymers; Swollen hydrogel; Swollen hydrogel; Degree of crosslinking; Cellulose; Cellulose(carboxymethyl); Absorbent material; Molecular structure; Swelling; Crosslink density; NMR spectrometry; Experimental study; Compression test; Colloidal gel; Solid state; Mechanical method; Measurement method; Cellulose ether; Cellulose(hydroxyethyl); Comparative study
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(02)00939-4

The network structure of a cellulose-based superabsorbing material has been probed by using three different techniques: 13C solid state NMR, free swelling in water and uniaxial compression of water swollen samples. A good agreement between the three apporaches has been found in terms of concentration of crosslinks per unit volume.
The results have been discussed taking into account that NMR technique is able to detect only chemically effective crosslinks while free swelling and compression are sensitive to elastically effective physical and chemical crosslinks.
A depression of swelling capacity and an apparent increase of degree of crosslinking with time, promoted by ageing of the cellulosic material, has been experimentally evidenced and discussed in terms of development of intermolecular physical interactions.