Sublimation printing involves transferring a solid ink to a gas that permeates a coating without experiencing the liquid state- this requires pressure, heat, and a special base or coating to the product you wish to print in. That's why you can't just throw a white coffee mug in a press and print onto it- it has to be specially treated first.
We've researched this with polymer clay and also tried it out- unfortunately, the quick answer is no. The reason for that is polymer clay cures at 275F, or around that temperature. Sublimation products require a much higher temperature for curing. You can't cure the coating onto the clay during the cure process because they need two different temperatures.
Theoretically you can try, but the substrate (this is a coating you need to put on your item) that accepts the inks cures at 350F, which blackens polymer clay and turns it into a "lumpy black charred marshmallow" looking thing.
Then once the substrate is cured, the piece has to be heated again, under pressure, and for at least 5 minutes for the inks to penetrate the coating.
So the whole process is just not suited to polymer clay as a base.
If you want to sublimate onto a pendant or jewelry, we suggest you check out someplace that sells bisque- this is a ceramic that has been fired once and not glazed yet. Ceramic pieces are much better suited to sublimating. Have fun!