Ion-triggered exfoliation of layer-by-layer assembled poly(acrylic acid)/poly(allylamine hydrochloride) films from substrates: A facile way to prepare free-standing multilayer films

A facile way to prepare sheet- and tubelike free-standing films of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) was developed by exfoliating PAA/PAH multilayer films from substrates in acid aqueous solution containing copper ions. The exfoliation of the PAA/PAH film from the substrate was achieved by breaking the electrostatic interaction of the PAA layer with the underlying substrate while keeping the integrity of the resultant films. Further study shows that thermally cross-linked freestanding PAA/PAH film can be prepared by treating the film in acid aqueous solution with a pH of 2.0. The ion-triggered exfoliation of PAA/PAH multilayer film provides a simple and flexible way to prepare layer-by-layer (LbL.) assembled free-standing multilayer films.