I am no expert on this stuff, but here is some brief things I found on a quick google search.
Here are the one's wiki lists, and are likely most common (in order of descending R value)
Polyisocyanurate spray foam
"...relatively strong molecular structure, because of the combination of strong chemical bonds, the ring structure of isocyanurate and high cross link density, each contributing to the greater stiffness than found in comparable polyurethanes. The greater bond strength also means these are more difficult to break, and as a result a PIR foam is chemically and thermally more stable: breakdown of isocyanurate bonds is reported to start above 200°C, compared with urethane at 100 to 110°C."
So, perhaps a bit better than straight polyurethane...
Closed-cell polyurethane spray foam
Phenolic spray foam
Seems this one is faily unstable, it will shrinks and can deteriorates in moisture or sunlight
"Icynene (LD-C-50™)1 is a low-density, open-cell
, water blown, polyurethane foam insulation that is made from petroleum-based plastics. Icynene LD-C-50 is a two-part, spray-applied product consisting of polymeric isocyanate (Component-A Base SealŪ) and a proprietary resin (Component-B, LD-C-50 Resin or Gold SealŪ)2."
Open-cell polyurethane spray foam