在过去的十年里,一种新的湿滑,被称为光滑共价附着液体表面(SCALS)的防粘表面已经出现,以接触角滞后值低为特征(CAH,小于5°)与水和大多数溶剂。尽管它们的纳米级厚度(1至5nm),SCALS表现出类似于润滑剂注入表面的行为,包括高液滴流动性和防止结冰的能力,缩放,和污垢。迄今为止,SCALS主要是使用接枝的聚二甲基硅氧烷(PDMS)获得的,虽然也有聚环氧乙烷(PEO)的例子,全氟聚醚(PFPE),和短链烷烃SCALS。重要的是,实现超低CAH的精确物理化学特性是未知的,使这些系统的合理设计成为不可能。在这次审查中,我们对CAH的报告值进行了定量和比较分析,分子量,接枝密度,和层厚度的范围的SCALS。我们发现CAH不会随着任何报告的参数单调缩放;相反,CAH最小值位于中间值。对于PDMS,在前进接触角为106°时观察到最佳行为,分子量在2至10kgmol-1之间,接枝密度约为0.5nm-2。对于从末端接枝链产生的层,SCALS上的CAH最低,并且随着结合位点的数量而增加,并且通常可以通过通过残留硅烷醇的封盖增加表面的化学均匀性来改善。我们回顾了关于SCALS的现有文献,包括目前制备方法的合成和功能方面。对报道的SCALS的性质进行了定量分析,揭示现有数据的趋势,并突出未来实验研究的领域。
Over the past decade, a new class of slippery, anti-adhesive surfaces known as slippery covalently-attached liquid surfaces (SCALS) has emerged, characterized by low values of contact angle hysteresis (CAH, less than 5°) with water and most solvents. Despite their nanoscale thickness (1 to 5 nm), SCALS exhibit behavior similar to lubricant-infused surfaces, including high droplet mobility and the ability to prevent icing, scaling, and fouling. To date, SCALS have primarily been obtained using grafted polydimethylsiloxane (PDMS), though there are also examples of polyethylene oxide (PEO), perfluorinated polyether (PFPE), and short-chain alkane SCALS. Importantly, the precise physico-chemical characteristics that enable ultra-low CAH are unknown, making rational design of these systems impossible. In this review, we conduct a quantitative and comparative analysis of reported values of CAH, molecular weight, grafting density, and layer thickness for a range of SCALS. We find that CAH does not scale monotonically with any reported parameter; instead, the CAH minimum is found at intermediate values. For PDMS, optimal behavior is observed at advancing contact angle of 106°, molecular weight between 2 and 10 kg mol-1, and grafting density of around 0.5 nm-2. CAH on SCALS is lowest for layers created from end-grafted chains and increases with the number of binding sites, and can generally be improved by increasing the chemical homogeneity of the surface through the capping of residual silanols. We review the existing literature on SCALS, including both synthetic and functional aspects of current preparative methods. The properties of reported SCALS are quantitatively analyzed, revealing trends in the existing data and highlighting areas for future experimental study.