|How does glue get objects to stick to it? Do molecules in the objects bind with molecules in the glue?
Ideally, the glue would form strong covalent bonds with the material and then form countless strong bridges from one object to another. Unfortunately, getting the glue to form such strong bonds with a surface is rarely possible. Instead, the glue forms weaker hydrogen bonds or van der Waals with the surface and is not so firmly attached. The glue's polymer molecules may also extend into the surface, in cracks and fissures to form a more sturdy attachment. Clearly, surface preparation can help the gluing process. Glue will bind more effectively to a porous, rough surface than to a very smooth, impermeable one.