Polydimethylsiloxane monolayer

V.M. Rudoy, Hydrolysis of polydimethylsiloxane monolayers on water surfaces, in. Chemistry and... 

Deposition of polymer layers on the porous stracture has similar effects and changes the stability and sensitivity of PSi-based devices as well (Vrkoslav et al. 2005 Xia et al. 2005 Benilov et al. 2007). For example, Xia et al. (2005) established that PDMS (polydimethylsiloxane) monolayers provide good protection and some characteristic improvement for PL of PSi. The measurements have shown that the PDMS monolayer provided a strong armature to PSi under a variety of stringent conditions such as in the base solution. Vrkoslav et al. (2005) also showed that impregnation of porous silicon with cobalt phthalocyanine (Co"Pc) is an effective way to improve the stability of the photoluminescence quenching response. 

Recently, Genzer and coworkers [85] presented an interesting new approach for the preparation of stable silane-based SAM systems. As a substrate, cross-linked polydimethylsiloxane (PDMS) was oxidized by UV/ozone treatment to yield a thin sihcon dioxide surface. The surface was then treated with fluorinated alkyltrichlo-rosilanes from the gas phase while being mechanically stretched by a certain length Ax. After modification, the elastomer was allowed to relax resulting in a mecdianically assembled monolayer (MAM) at the surface (Fig. 9.8). 

Keywords wrinkling Thin-film Elastomeric polymer Polydimethylsiloxane Patterns Deformation Surfaces Self-assembly Polyelectrolyte multilayer films Thin-films Polymer brushes Colloidal crystallization Mechanical-properties Assembled monolayers Buckling instability Elastomeric polymer Tobacco-mosaic-virus Soft lithography Arrays... 

Surface pressure was measured as a function of surface concentration for monolayers of linear and cyclic polydimethylsiloxanes. In addition, the comparisons of linear and cyclic polymer above the overlap concentration c lead to the surprising conclusion that even for three-dimensional semi-dilution solutions, the ratio c/c was not a universal reduced concentration [174]. 

It should be underlined that it was possible to obtain slip at low stress values, by considering the flow of a polydimethylsiloxane (PDMS) through a silica die with walls grafted by a fluorinated monolayer [11]. It can also be found in the experimental study published in 1993 by Migler et al. [12], which moreover validates the model prediction in term of extrapolation length, for sufficiently high slip velocities. 

For comparison with this material, a mixture of the homopolymers was examined. Portions of an anionically polymerized polymethyl methacrylate (Mn = 39,200) and a polydimethylsiloxane (Mn = 29,000) were combined to yield a mixture containing 42.2 wt % siloxane the mixture was spread to form a monolayer. Figure 7 shows the tt—A curve of this... 

From the results presented in Table 3.27 and in accordance with the results of [157, 158], for oirr case at 333 K, the surface layer at maximum adsorption (surfactant mass fractions from 2.25 x 10 to 7.5 X 10 is an extremely compressed monolayer, whereas the majority of dimethylsiloxane units lie on the surface of the liquid. At higher temperatures (343—353 K) but in a narrower concentration range (from 5 x 10 to 7.5 x 10 ) the polydimethylsiloxane chain tears off the sirrface, forming spiral turns of 6—8 elements, as witnessed by a single element area of 0.09-0.11 nm, which may be referred to one spiral turn [157]. From the concentration and tempera-... 

A metal overlayer ATR-FTIR technique which markedly enhances the SNR of monolayer and submonolayer film spectra has been described. The metals investigated were gold and aluminium, with a substrate of polyether-urethane elastomer (375). The use of silver films under ATR geometry has improved the detection limit of the surface layer on polymer films. An enhancement factor of 10 and 2 is reported for polydimethylsiloxane and polycarbonate respectively, compared to the conventional ATR technique (362). 

In 2D cell culture on chip, cell adhesion has been extensively studied on patterned surfaces for it is critical to cellular functions. Micropattems have been used to study the cellular interactions with various materials such as metals, polymers, self-assembled monolayers, extracellular matrix proteins, cell adhesion peptides, and other bioactive molecules. The physical and chemical properties of a substrate affect the attachment and growth of cells on it, and many studies have demonstrated that different topographical features of a surface affect cell attachment. Glass, sflicon, and polydimethylsiloxane (PDMS) are widely used as substrate materials of ceU culture microchips. 

Plastic mold is fabricated by polydimethylsiloxane (PDMS). The chemical structure of PDMS is shown in Figure 4.20. A monolayer of DPE (4,4-diami-nodiphenylether) is coated on the plastic mold. The monolayer is transferred to the base plate. After stripping of the plastic mold, a multilayer of terephthaloyl chloride (TPC) and DPE is self-assembled on a monolayer by vapor deposition, as shown in Figure 4.21. The multilayer is then hardened by condensation polymerization. The reaction scheme of condensation polymerization is shown in Figure 4.22. The final pattern on the base plate is obtained after etching and resist removal. 

Fig. 3 Isotherms of Polydimethylsiloxane (1 kg/mol) with hydrophilic head groups [15]. The first plateau at zero surface pressure indicates the transition from a gaseous state to a monolayer with respect to the repeat units. The second plateau at roughly 10 mN/m indicates the transition from a monolayer with respect to the repeat units to a melt brush Data taken from ref. [15]...

Microcontact printing (12-14) of self-assembled monolayers was carried out using a patterned polydimethylsiloxane stamp to print a 2mM ethanolic solution of the relevant thiol onto gold-coated silicon substrates. 

The thickness profiles of microdroplets of polydimethylsiloxane (PDMS) oligomers deposited on oxidized silicon wafers exhibit equal thickness steps, each 0.7 nm thick (Fig. 5.4). The number of visible steps, their lengths, and their growth d3mamics depend on the surface chemistry of the wafers. The common step thickness is the transverse size of the PDMS chain, which means that each step corresponds to a compact flat monolayer of chains, that is, a 2D nonvolatile liquid. Information on the disjoining pressure, and on the friction coefficients between successive layers, can be extracted. " The d3mamics of adsorption of silanol ends when silanol-terminated PDMS (PDMS-OH) is deposited on the wafer can also be monitored in real time. ... 

Figure 15.2 Examples of 2D layers fabricated by convective assembly, [a] Examples of a crystal monolayer obtained from 1.1 jam PS latex particles. The crystalline order leadingto bright diffraction is revealed when illuminated with a white light from behind. [b) SEM images of a 100 nm gold nanoparticles monolayer assembled on a silicon surface (unpublished results], a monolayer (c], and a bilayer (d] obtained with 500 nm PS particles. The structures were first assembled on a flat PDMS substrate and then transferred onto a silicon wafer by printing. Abbreviations SEM, scanning electron microscopy PDMS, polydimethylsiloxane PS, polystyrene.

S. Ross, G. Nishioka. Monolayer studies of silica/polydimethylsiloxane dispersions. /. Colloid Interface Sci., 65,216-224,1978. 

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