Everyone has a favourite experiment, and this is one of mine. The look on the student's faces when the nylon is pulled from the interface.
Pour 5 cm3 of the aqueous diamine solution into a 25 cm3 beaker. Carefully pour 5 cm3 of the cyclohexane solution of the acid chloride on top of the first solution so that mixing is minimised. This is because the oil floats on the water layer. Do this by pouring the second solution down the beaker's wall or a glass rod.
The cyclohexane will float on top of the water without mixing.
Place the beaker below a stand and clamp it. A greyish film of nylon will form at the interface.
Pick up some of this with tweezers and lift it slowly and gently from the beaker. It should draw up behind it a thread of nylon.
Pull this over the rod of the clamp so that this acts as a pulley.
Continue pulling the nylon thread at a rate of about half a metre per second. It should be possible to pull out several metres.
The thread will be coated with unreacted monomer and maybe a narrow, hollow tube filled with monomer solution. Wearing disposable gloves is essential.
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