PDMS, oxidation

In a separate study using the JKR technique, Chaudhury and Owen [48,49] attempted to understand the correlation between the contact adhesion hysteresis and the phase state of the monolayers films. In these studies, Chaudhury and Owen prepared self-assembled layers of hydrolyzed hexadecyltrichlorosilane (HTS) on oxidized PDMS surfaces at varying degrees of coverage by vapor phase adsorption. The phase state of the monolayers changes from crystalline (solidlike) to amoiphous (liquid-like) as the surface coverage (0s) decreases. It was found that contact adhesion hysteresis was the highest for the most closely packed... 

Effect of phase state of monolayers of hexadecylsiloxane supported on oxidized PDMS-hysteresis in interfacial energetics as determined by contact mechanics and contact angles... 

Surface energies of different end-functionalized trichlorosilane monolayers self-assembled on oxidized PDMS ... 

Fig. 12. Schematic of a polymer-coated crosslinked PDMS cap in contact with a polymer-coated flat surface. The PDMS cap is oxidized in 02-plasma, and the polymer layer is coated by solvent casting. On flat surface, the polymer layer is spin coated.

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. 

Synthesis of comb (regular graft) copolymers having a PDMS backbone and polyethylene oxide) teeth was reported 344). These copolymers were obtained by the reaction of poly(hydrogen,methyl)siloxane and monohydroxy-terminated polyethylene oxide) in benzene or toluene solution using triethylamine as catalyst. All the polymers obtained were reported to be liquids at room temperature. The copolymers were then thermally crosslinked at 150 °C. Conductivities of the lithium salts of the copolymers and the networks were determined. 

OS 80] [R 7] [P 60] The acid-catalyzed dehydration of of 1-hexanol to hexene was conducted in a micro reactor made of PDMS, which also contained a heahng fimc-hon [19, 138], Sulfated zirconium oxide was coated as catalyst on the top plate of the micro reactor. A yield of 85-95% was obtained by-products could not be detected. This performance exceeds those of conventional reactors (30%). 

The PDMS-membrane-occluded FePcY was the first room temperature catalytic membrane and the first solid catalyst dispersed in dense organic polymer.169 The catalytic system mimics the cytochrome P-450 enzyme and can oxidize alkanes at room temperature with rates comparable to those of the... 

Strain-induced crystallization would presumably further improve the ultimate properties of a bimodal network. It would therefore obviously be of considerable importance to study the effect of chain length distribution on the ultimate properties of bimodal networks prepared from chains having melting points well above the very low value characteristic of PDMS. Studies of this type are being carried out on bimodal networks of polyethylene oxide) (55), poly(caprolactone) (55), and polyisobutylene (56). 

In order to obtain a nano-hybrid with higher mechanical properties, PDMS was replaced with poly(tetramethylene oxide) (PTMO) [41]. PTMO-Ti02 nano-hybrids were prepared by a sol-gel method from triethoxysilane functionalized PTMO (Si-PTMO) and tetraisopropyltitanate with weight ratios of 30/70, 40/60 and... 

Figure 10.4 Temperature profiles for three classes of analytes monoterpenes (limonene) sesquiterpenes [(3 caryophyllene, caryophyllene oxide (caryo. oxide)] and diterpenes [cem brene A, isoincensole acetate (iso. acetate)]. PDMS fibre, sampling time 40 min. Reproduced from S. Hamm, E. Lesellier, J. Bleton, A. Tchapla, J. Chromatogr., A, 1018, 73 83. Copyright 2003 Elsevier Limited...

In practice, some anticoagulation agents such as heparin or antiplatelet agents, e.g. nitric oxide (NO) are delivered to sensor sites in order to reduce the risk of thrombus formation. Nitric oxide (NO), which is a potent inhibitor of platelet adhesion and activation as well as a promoter of wound healing in tissue, has been incorporated in various polymer metrics including PVC (poly(vinyl-chloride)), PDMS (poly-dimethyl-siloxane) and PU (poly-urethanes). Those NO release polymers have been tested in animals as outer protection coatings and have shown promising effects for the analytical response characteristics of the sensor devices [137],... 

Kim, Y.-K. Kim, G T. Ha, J. S. 2007. Simple patterning via adhesion between a buffered-oxide etchant-treated PDMS stamp and a Si02 substrate Adv. Fund. Mater. 17 2125-2132. 

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