Nanowerk August 17, 2023
Slippery covalently attached liquid surfaces (SCALS) with low contact angle hysteresis (CAH) and nanoscale thickness display impressive anti-adhesive properties, like lubricant-infused surfaces. Their efficacy is generally attributed to the liquid-like mobility of the constituent tethered chains. However, the precise physico-chemical properties that facilitate this mobility are unknown. An international team of researchers (Australia, Germany) quantified the chain length, grafting density, and microviscosity of a range of polydimethylsiloxane (PDMS) SCALS, elucidating the nanostructure responsible for their properties. They used three methods to produce SCALS, with characterization carried out via single-molecule force measurements, neutron reflectometry, and fluorescence correlation spectroscopy. CO2 snow-jet cleaning was shown to reduce the CAH of SCALS via a modification of their grafting density. SCALS behavior could be predicted by reduced grafting density, Σ, with the lowest water CAH achieved at Σ ≈ 2. According to the researchers their study provides the first direct examination of SCALS grafting density, chain length, and microviscosity and supports the hypothesis that SCALS properties stem from a balance of layer uniformity and mobility… read more. Open Access TECHNICAL ARTICLE