Sticky Monolayers and Defect-Free Langmuir−Blodgett Bilayers Using Poly(acrylamide) Glue

Abstract

The introduction of poly(acrylamide) (PAM, Mw 10 000) to an aqueous subphase resulted in increased intermolecular association in the monolayer formed from 5,11,17,23,29,35-hexaamideoxime-37,38,39,40,41,42-hexakis(1-hexadecyloxy) calix[6]arene (2) at the air−water interface, as evidenced by surface viscosity measurements. Langmuir−Blodgett (LB) bilayers of 2, which were deposited onto silylated silicon wafers, showed the presence of PAM, as determined by X-ray photoelectron spectroscopy (XPS). On the basis of XPS analysis at two different takeoff angles (15 and 75°), both the amidoxime groups of the calix[6]arene and the amide groups of PAM, appear to be buried within the LB bilayer. Deposition of single LB bilayers of 2 containing PAM onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) supports and measurement of their their permeability with respect to He, N2, and CO2 showed a substantial improvement in their permeation selectivity properties, compared with analogous membranes that were devoid of PAM. Taken together, these results indicate that the use of nonionic, water-soluble polymers that are capable of hydrogen bonding with surfactant monolayers have considerable promise as “gluing” agents for enhancing the cohesiveness and quality of corresponding LB films.