1H-13C CPMAS and T2 relaxation solid-state NMR measurements of melamine-based polycondensed chemical gels

Gel networks prepared from aqueous melamine-formaldehyde resins via a sol-gel route were characterised by C-13 CPMAS (where AAAS stands for magic angle spinning)-NMR and T-2 relaxation. We show that within the aqueous networks, the type and amount of functional groups on the melamine ring is strongly influenced by the initial melamine/formaldehyde ratio, the sol concentration and the amount of catalyst. Residual methylol groups can be etherified by postalkoxylation using primary alcohols resulting in chemical gels with different bridging units and residual ether linkages as also confirmed by T-2 measurements. In addition, in the case of initially alkoxylated gels the alcoholysis process can be followed by varying the amount of catalyst used.