Sugar-sensitive dendrimer films as a sacrificial layer for the preparation of freestanding multilayer films

Multilayer thin films composed of poly(vinyl alcohol) (PVA) and phenylboronic acid-bearing poly(amidoamine) dendrimer (PBA-PAMAM) were used as a sacrificial layer for constructing freestanding polyelectrolyte films consisting of poly(styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). Freestanding (PSS/PAH)₁₅ films were successfully released from substrate by exposing composite (PVA/PBA-PAMAM)_n/(PSS/PAH)₁₅ films (n=5 and 10) to sorbitol solutions under mild conditions at pH7.0-9.0. The film release was accelerated in solutions of higher sorbitol concentrations at pH9.0 as well as in solutions with lower concentration of NaCl. The results were rationalized based on the scission of boronate ester bonds between PBA-PAMAM and PVA in the (PVA/PBA-PAMAM)_n layer due to a competitive binding of sorbitol to PBA-PAMAM.