Water absorption and transport in bis-silane films

Area of Science:

• Materials Science
• Polymer Science
• Surface Chemistry

Background:

• Understanding water absorption in silane films is crucial for applications in coatings and protective layers.
• Silane-based materials are widely used, but their interaction with water can affect performance and durability.

Purpose of the Study:

• To investigate the mechanism and extent of heavy water (D2O) ingress into bis-amino silane and bis-sulfur silane films.
• To elucidate the relationship between water absorption and film swelling in these silane systems.

Main Methods:

• In situ neutron reflectivity was employed to quantitatively measure D2O absorption and film thickness changes.
• Analysis focused on the volume of D2O absorbed and the corresponding volumetric changes (swelling) of the silane films.

Main Results:

• Bis-amino silane films absorbed significantly more D2O (33 vol%) compared to bis-sulfur silane films (4.6 vol%).
• The volume increase (swelling) of both film types was considerably less than the total D2O absorbed.
• Evidence for dual-mode sorption (Henry's and Langmuir modes) was observed, with the Langmuir mode dominating and explaining the limited swelling.

Conclusions:

• Water absorption in these silane films follows a dual-mode sorption mechanism, involving both dissolution and occupation of free volume.
• The dominance of the Langmuir mode in water sorption is responsible for the observed minimal film thickness changes.
• A two-stage swelling process, characterized by an initial rapid increase followed by a slower phase, supports the dual-mode sorption model.