PDMS, bonding

A study of the effect of 02 plasma parameters on PDMS bonding shows that low RF power and short treatment time are better than higher RF power and long treatment time, respectively, for bonding instantly after plasma treatment. Moreover, the bonding has to be carried out within 15 min after the plasma treatment to ensure complete bonding [175]. 

K. Haubert, T. Drier and D. Beebe, Pdms bonding by means of a portable, low-cost corona system, Lab on a Chip, 6(12), 1548-1549 (2006). 

Concentration Gradient Generation and Controi, Fig. 5 Design and layout of the ladder chamber, (a) The chamber was fabricated from PDMS bonded to glass and consists of two main chaimels connected by bridge channels, (b) Constant flow in the main chaimels allows steady-state diffusion in the microgrooves... 

Table 9.4 shows solid surface energy data for the first PMTFPS sample listed in Table 9.3. Also included for comparison are PDMS from She et al. [18] and PTFE data taken from the compilation by Owen [19]. The She measurements are for a very thin film of PDMS, bonded to a smooth silicon wafer, that had very low contact angle hysteresis, only 3° difference between the advancing and receding water contact...

M. A. Eddings, M. A. Johnson, and B. K. Gale, "Determining the optimal PDMS-PDMS bonding technique for microfluidic devices," Journal of Micromechanical Microengineering, vol. 18, p. 067001,2008. 

She et al. [128] used rolling contact to estimate the adhesion hysteresis at polymer/oxide interfaces. By plasma oxidation of the cylinders of crosslinked PDMS, silica-like surfaces were generated which could hydrogen bond to PDMS r olecules. In contrast to unmodified surfaces, the adhesion hysteresis was shown to be larger and proportional to the molecular weight of grafted polymer on the substrate. The observed hysteresis was interpreted in terms of the orientation and relaxation of polymer chains known as Lake-Thomas effect. 

As another consequence of the properties of the siloxane bond, the value of n in the common linear trimethylsiloxy-endblocked-PDMS, (M-D -M) can vary from zero to tens of thousands giving a range of viscosity from 0.65 to 2,500,000 centipoise to the polymeric material. This relationship between viscosity and polymer chain length allows PDMS polymers to vary in form from water-like fluids to a flowable gum, while retaining the same chemical character. 

PDMS based siloxane polymers wet and spread easily on most surfaces as their surface tensions are less than the critical surface tensions of most substrates. This thermodynamically driven property ensures that surface irregularities and pores are filled with adhesive, giving an interfacial phase that is continuous and without voids. The gas permeability of the silicone will allow any gases trapped at the interface to be displaced. Thus, maximum van der Waals and London dispersion intermolecular interactions are obtained at the silicone-substrate interface. It must be noted that suitable liquids reaching the adhesive-substrate interface would immediately interfere with these intermolecular interactions and displace the adhesive from the surface. For example, a study that involved curing a one-part alkoxy terminated silicone adhesive against a wafer of alumina, has shown that water will theoretically displace the cured silicone from the surface of the wafer if physisorption was the sole interaction between the surfaces [38]. Moreover, all these low energy bonds would be thermally sensitive and reversible. 

In silicone adhesives used to bond structural glazing assemblies, the silicone network is made of very long PDMS chains and is filled with silica that improves the elastomeric properties of the adhesive. The strength of such an adhesive is strongly enhanced through various mechanisms of energy absorption. 

The chemical modification techniques refer to the treatments used to modify the chemical compositions of polymer surfaces. Those can also be divided into two categories modification by direct chemical reaction with a given solution (wet treatment) and modification by covalent bonding of suitable macromolecular chains to the polymer surface (grafting). Among these techniques, surface grafting has been widely used to modify the surface of PDMS. 

The gases resulting from the irradiation of PDMS have been reported in the literature [395] and consist entirely of hydrogen, methane, and ethane. The yield has been found to be proportional to the degree of cross-linking since double bonds cannot be formed. 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

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