Polyisoprene is a naturally occurring polymer, so it wasn't exactly "discovered" in the way that a new chemical compound might be. However, we can identify some key figures in its understanding and utilization:

* Nature: Plants are the primary source of polyisoprene, specifically in the form of natural rubber. It's been used by humans for millennia.

* Charles Goodyear (1839): Goodyear's vulcanization process was crucial in making natural rubber more durable and useful. This revolutionized the use of polyisoprene.

* Carl von Naegeli (1878): Naegeli was the first to propose that natural rubber was a polymer, though he didn't know the specific structure of the repeating unit.

* Hermann Staudinger (1920s): Staudinger established the concept of macromolecules and determined that natural rubber was a polymer of isoprene.

So, while polyisoprene itself was "discovered" by nature, the credit for understanding its structure and improving its use goes to these individuals and many others throughout history.