Polaris OBark

I'm also a chemist.

I remain skeptical that there is any difference apart from the solvent.

If the solvent isn't the critical difference, why would they use a carcinogenic one?

If I had to guess, [this is wrong; see below] trichloroethylene dissolves the surface layer of the butyl tube a little bit better than n-heptane. It works as a contact cement, so the solvent essentially enables the rubber contact glue to bond to the tube surface as it evaporates. Then the little bit of adhesive on the patch sticks to the tacky surface created on the tube as the solvent evaporates, and the patch bonds to the tube as you apply pressure.

(I've used the little tubes primarily because the solvent dries up after you open it, not because I think it is magically different from rubber cement, which would probably be more than adequate. I found out the hard way the patch works reasonably well even in the absence of any cement.)