Electrostatic Deposition of Polyionic Monolayers on Charged Surfaces

Abstract

We explored molecular films of polyionic materials built by electrostatic deposition on a charged surface. Formation of self-assembled monolayers is monitored for poly(styrenesulfonate) (PSS) adsorbed on charged surfaces of amine-terminated self-assembled monolayer (SAM) and poly(allylamine) (PAA) on a PSS monolayer. In both cases, polyions are adsorbed on oppositely-charged surfaces. Observations of PSS monolayers at various stages of electrostatic deposition reveal inhomogeneous self-assembly at the earliest stages of deposition. During the first several minutes of deposition, negatively-charged PSS macromolecules tend to adsorb on selected defect sites of positively-charged SAM (scratches, microparticles, and edges) and form islands composed of PSS coils. At this stage, electrostatic adsorption of PSS chains is predominant and equilibration of the surface structure is not achieved by the slow surface diffusion mechanism. Only longer deposition times (>10 min) result in an equilibration of polymer layers and formation of a homogeneous thin PSS layer composed of highly flattened macromolecular chains. The monolayer thickness is between 1.0 and 1.5 nm, with a microroughness of about 0.2 nm. Self-assembly of a second PAA layer on top of a PSS monolayer follows similar tendencies, resulting in the formation of homogeneous PAA/PSS bilayers with an overall thickness of 1.7−2.5 nm.

Ultrathin polymer coatings by complexation of polyelectrolytes at interfaces: suitable materials, structure and properties

“…Also, their smooth surface renders them well suited for X-ray reflectivity studies 131,312,381,382,385) and for near-field microscopy. For these purposes, mica 75,103,104,201,252,253,281,316,323,348,386,387) and float glass 19,80,131,180,182,184,185,388,389) present alternatives. Gold coated surfaces enable electrochemical studies 86,196,205,209,211,340,354,390,391) , investigations by quartz crystal microbalance (QCM) 65,86,102,119,130,202,238,266,279,305,338,339,350,…”

“…The silanol groups at the surface of glass and quartz, as well as of silicon wafers due to the thin surface layer of oxide, can be easily deprotonated by base. Treatment with various functionalized silanes, such as trialkoxy-3-aminopropylsilane 113,114,143,200,219,227,286,388,395) , provides an additional, "easy" access to positively charged surfaces. In a similar way, treatment of gold with functionalized thiols or disulfides, respectively, enables the tailoring of both positively (e. g. when applying cysteamine 119,211,277,296,387) ) or negatively (e. g. when applying mercaptoundecanoic acid 115,116,228,269,286,396,397) ) charged surfaces.…”

“…In any case, molar mass effects, pH and ionic strength may influence the kinetics, and adsorption kinetics seem to be transport-limited only in the very beginning of the process 129) . In fact, several studies indicate that polyion adsorption is a twostep process: polymer chains are anchored to the surface by some segments during a fast initial step, and then relax to dense packing during a slower second step 29,34,63,85,191,306,388,426) . This second step may take much time.…”

Electrophoretic separation of neurotransmitters on a polystyrene nano-sphere/polystyrene sulphonate coated poly(dimethylsiloxane) microchannel

“…It is due to the elasticity of PDMS that provided the effects as keystone, clamp and/or anchor, and hydrophobic interaction between PSNS and PDMS. 31,32 After that, PSS solution was pumping through that coated channel for 1 h. According to previous report, 33 negatively charged PSS could be adsorbed on those positively charged PSNS. SCHEME 1.…”

Morphological Structure Characterization of PAH/NiTsPc Multilayer Nanostructured Films

“…A two-stage adsorption process was also pro posed by Raposo [34] and Tsukruk [35]. It is possible to use the Avrami parameter n to distinguish between growth on the interface or by diffusion.…”