Spatially Resolved Monitoring of Drying of Hierarchical Porous Organic Networks

MANUEL VELASCO; EMILIA SILLETA; CESAR GOMEZ; MIRIAM STRUMIA; SIEGFRIED STAPF; GUSTAVO MONTI; RODOLFO ACOSTA

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2016 p. 2067 - 2074

0743-7463

Evaporation kinetics of water confined in hierarchal polymeric porous media is studied by low field nuclearmagnetic resonance (NMR). Systems synthesized with various degrees of cross-linker density render networks with similar poresizes but different response when soaked with water. Polymeric networks with low percentage of cross-linker can undergoswelling, which affects the porosity as well as the drying kinetics. The drying process is monitored macroscopically by single-sidedNMR, with spatial resolution of 100 μm, while microscopic information is obtained by measurements of spin−spin relaxationtimes (T2). Transition from a funicular to a pendular regime, where hydraulic connectivity is lost and the capillary flow cannotcompensate for the surface evaporation, can be observed from inspection of the water content in different sample layers.Relaxation measurements indicate that even when the larger pore structures are depleted of water, capillary flow occurs throughsmaller voids.1.