title: pH-sensitive bipolar ion-permselective ultrathin films.
abstract: pH-Sensitive bipolar ion-permselective films of polyelectrolyte multilayers were prepared by layer-by-layer (LbL) assembly and photo-cross-linking of benzophenone-modified poly(acrylic acid) (PAA-BP) and poly(allylamine hydrochloride) (PAH-BP). The multilayer structure and ionizable group composition was finely tuned by changing the pH of the dipping solution. This structure and composition was in turn "preserved" by photo-cross-linking, forming highly stable membrane films. Since PAA-BP and PAH-BP are weak polyelectrolytes, it is possible to control the number of unbound, un-ionized -COOH or -NH2 groups in the multilayer by changing the pH. Moreover, the pH of the deposited film also plays an important role in determining selective latter permselectivity. For example, PAA-BP/PAH-BP multilayers deposited from two pH conditions, pH = 3 (PAA-BP) and pH = 6 (PAH-BP), showed pH-switchable permselectivity for both cationic (pH = 10) and anionic (pH = 3) probe molecules in a single film. The system offers advantages in film stability and introducing reversible selective ion permeability over previous multilayer film and cross-linking methods.
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
authors.forename: Mi-Kyoung
authors.initials: MK
authors.lastname: Park
authors.forename: Suxiang
authors.initials: S
authors.lastname: Deng
authors.forename: Rigoberto C
authors.initials: RC
authors.lastname: Advincula