I was going to become a polymer scientist, but didn't because I thought the work would be too repetitive.

Explanation: The word "polymer" describes any material with more two types of repeating chemical units, usually in the form of a long chain. Examples include materials such as DNA (your genetic code), nylon, polyethylene terephthalate (or PETE, used in plastic bottles), pectin (in fruit), wool, cellulose (in wood), and silk.