Switchable foam control by a new surface-active ionic liquid

A new surface-active ionic liquid 4-butylazobenzene-4′-ethoxy-trimethylammonium bis(trifluoromethanesulfonyl)imide ([BAzoTMA][NTf2]) was designed and synthesized to achieve reversible foaming–defoaming by alternatively adding cucurbit[7]uril (CB[7]) and spermine, which was investigated by measurements of contact angle and conductivity, 1HNMR, and PM-IRRAS.