Topological Insight into Superabsorbent Hydrogel Network Structures: a 1H Double‐Quantum NMR Study

Superabsorbent polymer (SAP) hydrogels have pronounced water‐absorbing and water‐storing capacities, which are essential for numerous potential applications. It remains a challenge to better understand the network topology because of their amorphous and anisotropic structures. Synthesis parameters such as monomer concentration, degree of neutralization and crosslinking, and surface crosslinking are varied to correlate structural changes in the network with low‐field proton double‐quantum (1H DQ) NMR results. 1H DQ‐NMR data are processed by a reliable, user‐independent analysis approach to determine the fractions of network defects, of mobile sol components, and of network chains as well as the residual dipolar coupling distribution in SAPs. In addition, results obtained by applying different distributions to describe the DQ buildup curves are quantified and compared. The correlation between topological and synthesis parameters as well as the impact of temperature, swelling, and solvent of SAP on DQ signals is investigated and discussed. Superabsorbent hydrogel network structures are investigated by low‐field proton double‐quantum (1H DQ) NMR. A user‐independent approach is proposed for reliable data processing, opening up the possibility for automation of data analysis regarding quality control application of low‐field 1H DQ‐NMR. The results lead to a better understanding of the network topology, local mobility, and heterogeneity of hydrogels and their correlation with synthesis parameters.