Rubber tires were in use long before anyone knew much about the science of polymers. This board gives a history of the commercialization, engineering, and science behind rubber tires: http://www.rubber.org/100th-anniversary2
I read down thru #52 and remembered that, when I was in college chemistry, the Thiokol solid rocket propellant plant was nearby. So, when I learned polysulfide rubber was called "Thiokol" rubber, I made my own "propellant" by synthesizing a batch of polysulfide rubber and adding potassium nitrate as an oxidizer. It worked, but left a residue. (I later learned that Thiokol used ammonium perchlorate as their oxidizer...)