title: The effect of guanidinium functionalization on the structural properties and anion affinity of polyelectrolyte multilayers.
abstract: Poly(allylamine hydrochloride) (PAH) is chemically functionalized with guanidinium (Gu) moieties in water at room temperature. The resulting PAH-Gu is used to prepare polyelectrolyte multilayers (PEMs) with poly(sodium 4-styrene sulfonate) (PSS) via layer-by-layer deposition. The polyelectrolyte (PE) adsorption processes are monitored real-time by optical reflectometry and a quartz crystal microbalance with dissipation monitoring (QCM-D). Compared to the reference PSS/PAH PEMs, the PSS/PAH-Gu PEMs show a lower amount of deposited PE materials, lower wet thickness, higher stability under alkaline conditions and higher rigidity. These differences are rationalized by the additional Gu-SO3(-) interactions, also affecting the conformation of the PE chains in the PEM. The interactions between the PEMs and various sodium salts (NaCl, NaNO3, Na2SO4 and NaH2PO4) are also monitored using QCM-D. From the changes in the frequency, dissipation responses and supportive Reflection Absorption Infrared Spectroscopy it is concluded that Gu-functionalized PEMs absorb more H2PO4(-) compared to the Gu-free reference PEMs. This can be understood by strong interactions between Gu and H2PO4(-), the differences in the anion hydration energy and the anion valency. It is anticipated that compounds like the presented Gu-functionalized PE may facilitate the further development of H2PO4(-) sensors and ion separation/recovery systems.
authors.affiliation: Organic Materials and Interfaces, Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands. l.c.p.m.desmet@tudelft.nl.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Cao
authors.forename: Pavlo I
authors.initials: PI
authors.lastname: Gordiichuk
authors.forename: Katja
authors.initials: K
authors.lastname: Loos
authors.forename: Ernst J R
authors.initials: EJ
authors.lastname: Sudhölter
authors.forename: Louis C P M
authors.initials: LC
authors.lastname: de Smet