Much Later
We never solved the issue of mass transfer, where the newer it was the more would be released. So, the odor would be too strong for the first week, then nice for a few, then barely detectable for a couple.
Glade released one in the 90s, where the heating element got gradually warmer over time so the release rare was more or less constant. I don't know if that's still on the market or not. That was at least 10 years after I worked on that project.
We were able to successfully do it with a dimethyl sulfate quaternary that would stick to the dryer drum and release fabric softener a little at a time. P&G sold Downy in that form, but it didn't catch on so they discontinued it.
Also, I later worked on synthesizing cinnamaldehyde using raw materials much cheaper than extraction from cinnamon bark. Very successful but I'm not sure if it was ever applied commercially.
Believe it or not, no matter how much one likes the fragrance of something, it gets very annoying when that's all one can smell for 4 or 5 weeks.
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