Sodium alginate is used in various industries, including food, pharmaceutical, and agriculture. Matrix systems, e.g., tablets, and granules, are macro samples with incorporated active substances. During hydration, they are neither equilibrated nor homogenous. Phenomena occurring during hydration of such systems are complex, determine their functional properties and hence require multimodal analysis. Still, there's a lack of comprehensive view. The study aimed to obtain unique characteristics of the sodium alginate matrix during hydration, particularly considering polymer mobilization phenomena using low-field time-domain NMR relaxometry in H₂O and D₂O. An increase in total signal during 4 h of hydration in D₂O of ca. 30 μV resulted from polymer/water mobilization. Modes in T₁-T₂ maps and changes in their amplitudes reflected physicochemical state of the polymer/water system: e.g. air-dry polymer mode (T₁/T₂ ~ 600) and two mobilized polymer/water modes (at T₁/T₂ ~ 40 and T₁/T₂ ~ 20). The study describes the approach to evaluating the hydration of the sodium alginate matrix in terms of the temporal evolution of proton pools: those existing in the matrix before hydration and those entering the matrix from the bulk water. It provides data complementary to spatially resolved methods like MRI and microCT.

Polyvinyl butyral (PVB) is an amorphous polymer employed in many technological applications. In order to highlight the relationships between macroscopic properties and dynamics at a microscopic level, motions of the main-chain and of the propyl side-chains were investigated between T_g − 288 °C and T_g + 55 °C, with T_g indicating the glass transition temperature. To this aim, a combination of solid state Nuclear Magnetic Resonance (NMR) methods was applied to two purposely synthesized PVB isotopomers: one fully protonated and the other perdeuterated on the side-chains. ¹H time domain NMR and ¹H field cycling NMR relaxometry experiments, performed across and above T_g, revealed that the dynamics of the main-chain corresponds to the α-relaxation associated to the glass transition, which was previously characterized by dielectric spectroscopy. A faster secondary relaxation was observed for the first time and ascribed to side-chains. The geometry and rate of motions of the different groups in the side-chains were characterized below T_g by ²H NMR spectroscopy.