Unveiling the origin of the anti-fogging performance of plasma-coated glass: Role of the structure and the chemistry of siloxane precursors

• Published in: Progress in organic coatings Vol. 141; p. 105401
• Main Authors: Durán, Iván Rodríguez, Profili, Jacopo, Stafford, Luc, Laroche, Gaétan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: 1,3,5,7-tetramethylcyclotetrasiloxane; Anti-fogging glass; Dielectric barrier discharges; Superhydrophilicity; Wettability; 1,3,5,7-tetramethylcyclotetrasiloxane; Wettability; Dielectric barrier discharges; Anti-fogging glass; Superhydrophilicity
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2019.105401

•Townsend discharges were used to obtain SiOxCy:H coatings using four siloxanes.•Only coatings prepared using TMCTS were anti-fogging.•Anti-fogging performance was due the presence of hydrophilic SiOH groups and appropriate surface roughness.•A cyclic siloxane structure is required to deposit an anti-fogging coating.•The presence of Si-H functionalities is a prerequisite for the formation of an anti-fogging coating. The application of (super)hydrophilic coatings in sectors of activity concerned by fogging, such as the food industry, the architectural sector, and medicine has attracted enormous attention over the past few years. However, despite this interest, most of the coating deposition techniques used thus far are not suitable for large-scale production because of their multistep nature. In this regard, the use of atmospheric pressure dielectric barrier discharges (AP-DBD) operated under a controlled N2/N2O atmosphere offers a promising alternative to conventional deposition techniques for the fabrication of anti-fogging coatings. Using this one-step coating approach, four siloxane precursors with different structures and different number of Si―H and Si−CH3 groups; namely, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), 1,1,3,3-tetramethyldisiloxane (TMDSO), and hexamethyldisiloxane (HMDSO) were deposited on glass samples. Because of their extreme wetting behavior (WCA < 5°), TMCTS-coated glasses featured an excellent anti-fogging performance, in contrast to OMCTS-, TMDSO-, and HMDSO-coated glasses which were not fogging-resistant (WCA ≈ 80°)). Coupled with hydrophilic functionalities, such as CO, O CO, and SiOH groups, the relatively high surface roughness of TMCTS-coated glass, compared with that of OMCTS-, TMDSO-, or HMDSO-coated glass, accounted for its superior visual characteristics when exposed to water vapor at 80 °C. These results allow us to confidently conclude that the cyclic structure of TMCTS in conjunction with the high reactivity of the Si-H bonds is responsible for the observed anti-fogging effect.