The way in which flexible polymers can modify the structure of a coated surface has been studied by measuring the interactions between polymer-bearing surfaces in liquids. It is observed that interactions induced by polymers attached to surfaces can also lead to striking changes in the effective 'wetting' properties of thin liquid films. A film is said to 'wet' a surface if it tends to spread uniformly on a solid surface. The smoothness and long-term stability of such films depends on how well they wet the surface, and this is essential for the electronic and electro-optical devices, for example, to work properly. If the films are to break up or 'dewet' the surface, the device would be of little use.