Might get some insight into Sealy Pure Cool from this:...

Might get some insight into Sealy Pure Cool from this:
http://www.freepatentsonline.com/20150067967.pdf
or in text at:
https://www.google.com/patents/US20150067967

[0028]
In each of the preferred embodiments of the foam mattress constructions, at least one of the upper layers and preferably a top foam layer includes a temperature control additive. In addition, at least one of the upper layers has a gel material in the foam, i.e. integrated into the cellular structure of the foam.
...
The polymer for the microspheres is selected for compatibility with the foam material. For the described mattress applications and constructions, a preferred PCM has a phase transition temperature range is 28-32 degrees C, such as are commercially available from Outlast Technologies, Inc.

So the PCM is in a gel in the top layer of foam down to a few millimetres then everything else is layers of different foam. I would imagine for it to work, the cap would also need to have a PCM as well.
I would imagine they need a non-gel PCM material in the fabric cap as well to maximise any effect