Self-Assembled Multilayer Films Based on Dendrimers with Covalent Interlayer Linkage

Abstract

Multilayer ultrathin films composed of nitro-containing diazoresin (NDR) as polycation and poly(amidoamine) dendrimers with carboxyl terminal groups (PAMAMC) (G = 1.5, 2.5, 3.5, and 4.5) as polyanion were fabricated on mica by electrostatic layer-by-layer deposition. Subsequent UV irradiation converted the interlayer linkage from ionic to covalent. The films were characterized with UV−vis, FTIR, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD). The results show that the uniform multilayer films were formed. All the films with dendrimers of various generations as building blocks have a very smooth surface with a mean roughness of about 0.8−1.1 nm. The thickness of the PAMAMC−NDR bilayer in the films increases with the generation number of the dendrimer, but the average thickness of the dendrimer monolayer is smaller than the diameter of the ideal spherical model of dendrimers with an extended conformation of all branches. They are significantly compressed in multilayer films. The conversion of the ionic to covalent linkage dramatically improved the stability of the films with respect to polar solvent, strong electrolyte, and surfactant solutions.

Influence of Co on Si3N4 incorporation in electrodeposited Ni

“…No significant improvement in hardness was observed for plain Co composite 325VHN. Similar observation has been reported for Ni-Co alloys with Co contents beyond 50 wt.% and their composites [10]. This has been associated with the hcp structure.…”

“…Thus, it is apparent that an increase in cobalt content beyond 14 wt.%, resulted in fortification of particle incorporation without enhancing the particle loading in the bath. Wang and Wei have reported that the trivalent Co ion catalyses the Ni-SiC composite plating [10]. An increase in the concentration of the trivalent cobalt ion resulted in an increase in SiC content in the deposits.…”

“…However, an increase to 41 wt.% of Co enhanced the hardness of the composite to 485VHN. This can be due to the combined effect of particle strengthening [10,11] and solid solution strengthening (Ni-38Co 446VHN), thereby refining the grain size and hardening the composite. A further increase in cobalt content to 70 wt.% resulted in a reduction in the hardness to 336VHN compared to Ni-41Co composite.…”

Sensitive Biosensors Based on (Dendrimer Encapsulated Pt Nanoparticles)/Enzyme Multilayers

“…In recent years, much attention has been paid to the construction of the third generation biosensor, which is based on the direct electron transfer between enzyme and electrode [5,6]. As a building unit for the multilayer films in biosensors, highly branched dendritic macromolecules are of great interest [7].…”

Covalent molecular assembly of multilayer dendrimer ultrathin films in supercritical medium

“…Similarly, Dai et al [21] prepared an ultrathin passivating film through layer-by-layer deposition of Gantrez and poly(allyamine) on an aluminum substrate followed by thermal treatment, forming interlayer imide bonds. Wang et al [22] used UV irradiation to convert ionic bonds formed during electrostatic layer-by-layer assembly of PAMAM and diazoresin to covalent.…”