A surface that has multiple physical materials?

So I am creating a game where different faces of the same object have different properties in how it interacts with the player. Part of the object when collided with will bounce the player away while another part will make the player 'stick'.

So far I have been assigning physical materials to objects, however this gives the whole object a single physical material. How can I give different parts of the object different physical materials? Would it be most efficient to just have objects of these types 'divided' into multiple children objects with each child object being the faces of the parent object that all have the same physical material? That seems a little lazy to me.