My startup's based around the tech I was studying for my PhD (I dropped out to do the startup, my research was leaning more real-worldy than academic, and to stay in academia I'd have had to go in a direction I didn't like). I'm pretty sure (in fact I've more or less been told) I could get the PhD within a couple of years without too much hassle, either full time or part time. I agree with another commenter's point that I might not actually enjoy it though!

Computer science is a little different from chemistry, though, it seems easier to jump in and out of academia like that.