Smart silicone coatings that can change their friction and stickiness

Research has led to a new way to make silicone surface and control their slipperiness

The structure of polymer brushes changes dramatically depending on the surrounding liquid

The investigation using neutron reflectometry and another technique, revealed how the brushes ‘grew’; how their internal structure responded to different liquids, and how those changes affected friction and adhesion 

Research led by a group from the University of Newcastle has found a new way to make silicone surfaces – and have even discovered that they can control how slippery they are. This work has been published this month in the journal Chemistry of Materials.   

Most of us have silicone in our homes, especially in the kitchen, it is often found as a rubbery coating that is usefully long-lasting, water-repellent and crucially—slippery.  Scientists have also wanted to make use of it at the nanoscale, where silicone has a big potential to reduce the friction of surfaces at this tiniest scale for use in medical devices and beyond. 

Because silicone is made up of long molecules, known as polymers, scientists have hoped to make surfaces where these molecules are gathered like a brush.  But silicone brush surfaces have been very hard to make and, critically, to control the surface properties. 

Using a controlled manufacturing technique called surface-initiated controlled polymerisation, the team grew exceptionally smooth and uniform silicone brush layers. The thickness of the brushes could be tuned from only a few nanometres to more than 70 nanometres.

A key discovery was that the structure of these brushes changes dramatically depending on the surrounding liquid. In water and simple alcohols, the polymer chains collapse tightly against the surface. In liquids such as toluene and hydrocarbons, similar to those found in lubricants, the chains take up solvent and extend away from the surface, creating a thicker, softer layer.