Variations of this are endless. I started using propane about 15 years ago. When choosing a cryogen there are many factors to consider including specific heat, thermal conductivity, relative cooling efficiency, viscosity at the cryogen melting point and thermal inertia. The best cryogens have high boiling points and and low freezing points. But for less critical work, like rapid quenching of polymer melts, it is sometimes helpful where working with a bottle of gas might not be allowed.
Propane gas liquefied by cooling is a much, much better cryo-agent than is isopentane.
Its easy to store in a lab a small gas cylinder with a blunt needle on a bit of tubing as the outlet. With little gas flow rub the needle over the small metal cup that is cooled by liq N2. Soon you will have a couple of ml of liquid propane. Do this in a fumehood, which is a good idea when using solvents too. Isopentane becomes very rubbery near liquid nitrogen temperature.