Poly bilayer structure

The simplest recording medium is a bilayer structure. It is constructed by first evaporating a highly reflective aluminum layer onto a suitable disk substrate. Next, a thin film (15-50 nm thick) of a metal, such as tellurium, is vacuum deposited on top of the aluminum layer. The laser power required to form the mark is dependent on the thermal characteristics of the metal film. Tellurium, for example, has a low thermal diffusivity and a melting point of 452 °C which make it an attractive recording material. The thermal diffusivity of the substrate material should also be as low as possible, since a significant fraction of the heat generated in the metal layer can be conducted to the substrate. For this reason, low cost polymer substrates such as poly (methylmethacrylate) or poly (vinyl chloride) are ideal. 

The bilayer morphology of thin asymmetric films of may be unstable. A regularly corrugated surface structure of the films was ascribed to spinodal transition into a laterally phase separated structure, where the surface morphology depended on the polymer incompatibility and the interfacial interactions [347, 348]. Recently, the phase separation and dewetting of thin films of a weakly incompatible blend of deuterated PS and poly(p-methylstyrene) have been monitored by SFM [349, 350]. Starting from a bilayer structure, after 454 h at T= 154 °C the film came to the final dewetting state where mesoscopic drops of... 

FIG. 6.16 Schematk representation of the deformation of photochromic airy rod"-KIthrough interaction with the water surface and the applied surface pressure, and the resulting bilayered structure of LBK films. 

A bilayer structure usually consists of two different films deposited on a substrate, one overlying the other. A typical system consists of a Pt substrate with an electro-deposited film of poly-[Ru(vbpy)3 ] on which a film of poly-[Os(bpy)2(vbpy)2" ] is elec-trodeposited (25). Another type of sandwich structure involves a pair of closely spaced electrodes such as in an electrode array (26), bridged by a polymer film. Alternatively, a different polymer can be deposited on each electrode of an array pair to form a bilayerlike arrangement having a junction where the films meet. Three-electrode devices of this type can produce a structure functionally equivalent to a field effect transistor (FET) (27). 

The interaction between an acidic phospholipid, the natural (wheat) phosphatidylinositolmonophosphate PI and a linear cationic polysoap the poly(2-methyl-5-vinyl-hexylpyridinium bromide) PVPC6 has been studied with mixed spread monolayers and with hydrated (40%, w/w) mixed bilayers. The "electrostatic" interaction between PI and PVPC6 involves monolayer condensation and affects the bilayers hydration. In addition, the free energy of the bilayers structural water is modulated by this interaction. 

Bilayer structures were prepared on cleaned silicon wafers (approximately 3 mm thick and 75 mm diameter) as follows 5 min exposure to oxygen plasma, followed by removal of native oxide layer by immersion into a solution of (10 2)% volume fraction HF and (5 2)% volume fraction NH3F in ultra pure water for (15 5) s. An oxide layer was regrown in a UV/Ozone chamber for (120 1) s followed by priming with hexamethyldisilazane vapor (HMDS). The lower layer consisting of the deutero-poly(butoxycarboxy styrene) (d PBOCSt) (Mr,n = 21000, = 2.1) was spin-coated from a propylene... 

A p-n-heterojunction type device can be fabricated on the basis of the junction formed between poly(pyrrole) and PT derivatives (e.g. PT or PMT) [784]. A PODT/Cfio junction device with a photo-induced charge transfer between PODT and Cgo is shown in Fig. 22 [449]. Rectifying bilayer electrodes with sequential bilayer structures are prepared from any pair of PBT/poly(pyrrole) and poly(3-bromothiophene)/poIy(pyrrole) by anodic electropolymerization on platinum electrodes [785]. 

Bilayer structures have been prepared and investigated with various spectroelectrochemical techniques [307, 486]. In the former report, surface resonance Raman spectroscopy showed typical vibrational features of the involved polymers [PANI and poly(o-phenylenediamine] as already discussed were observed. In the latter investigation, involving PANI/poly(5-chlorine,2-metho3 ani-line), it was concluded that the topmost layer of the polymerized substituted aniline blocks the electrochemical reduction of the inner layer of PANI. This was first deduced from the diminished height of reduction peaks in the CV. Moreover, this was supported by in situ UV-vis spectra that showed typictil bands of oxidized PANI even after formal reduction of the film. 

Poly-a-chloroacrylatcs do not exhibit Sc phases, only Sax phases. "Bilayer structures (Sai) are observed at shoit spacers (n 2). Despite their phases, the polymers 3a-3d could not be proved to be ferroelectric. No spontaneous polarization could be measured because of misalignment in the samples [14]. 

Figure 1 A generalized diagram of the structure of the cetostearyl alcohol gel found in topical and vaginal creams. The bilayers are formed principally of cetostearyl alcohol. The hydrophilic poly(oxyethylene) chains attached to the 5-carbon sorbitan rings in Polysorbate 60 retard water drainage from the interlamellar space and keep the lamellae from collapsing into a dense crystalline structure.

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