Diffusion in mesoporous materials and polymers swelling: a transient calorimetric approach

Area of Science:

• Materials Science
• Physical Chemistry
• Polymer Science

Background:

• Understanding diffusion dynamics in confined environments is crucial for material characterization.
• Differential Scanning Calorimetry (DSC) coupled with thermoporosimetry (TPM) offers a unique method to probe these processes.
• Mesoporous silica gels and cross-linked polydimethylsiloxane (PDMS) are relevant materials for various applications.

Purpose of the Study:

• To investigate the diffusion of water and benzene using DSC-TPM.
• To analyze the effect of confinement on water evaporation rates.
• To determine the mesh size distribution (MSD) of PDMS during swelling and drying cycles.

Main Methods:

• Utilized Differential Scanning Calorimetry (DSC) combined with the thermoporosimetry (TPM) technique.
• Monitored water diffusion during the drying of mesoporous silica gel at 40°C under dry air.
• Observed benzene diffusion during the drying and swelling of a cross-linked PDMS sample.

Main Results:

• Confinement was found to significantly affect the evaporation rate of water.
• Mesh size distributions (MSD) of the PDMS elastomer were calculated at various time points.
• The mean mesh size of the dry PDMS polymer was extrapolated to be approximately 2.5 nm.

Conclusions:

• DSC-TPM is an effective method for studying diffusion in porous and polymeric materials.
• Material confinement plays a critical role in controlling solvent evaporation.
• The TPM approach provides quantitative data on polymer network structure, such as PDMS mesh size.