Poly rubbed

In both procedures, a concern is the extent to which the poly(ethylene) undergoes wear within the artificial joint. The constant rubbing of metal on polymer is capable of generating particles of wear debris, and these can collect around the joint. In extreme cases, this debris can interfere with the metabolic processes in the remaining bone, leading to bone resorption and... 

FIGURE 5.8 Electroluminescence from an LED based on ITO-rubbed PPV-aligned poly(9,9-dioctyl fluorene)/Ca recorded through a polarizer oriented parallel (triangles) and perpendicular (circles) to the orientation direction. (From Whitehead, K.S., Grell, M., Bradley, D.D.C., Jandke, M., and Strohriegl, P., Appl. Phys. Lett., 76, 2946, 2000. With permission.)... 

M Flamaguchi and K Yoshino, Polarized electroluminescence from rubbing-aligned poly(2,5-dinonyloxy-l,4-phenylenevinylene) films, Appl. Phys. Lett., 67 3381-3383, 1995. 

M Jandke, P Strohriegl, J Gmeiner, W Brutting, and M Schwoerer, Polarized electroluminescence from rubbing-aligned poly(phenylenevinylene), Adv. Mater., 11 1518-1521, 1999. 

For example, a poly(disulfide) was obtained as a result of a two-electron transfer to 2,5-dithiocyanatothiophene in dry argon (Todres et al. 1979) (Scheme 7-8). This reaction provides a good reason to probe such very simple compounds as sources of lubricating films for rubbing metallic surfaces. 

Preliminary experiments indicated that a convenient charcoal diaphragm, permitting a reasonable flow rate of gas, was about 1 cm. in diameter and 0.2 to 1.0 mm. thick. A number of disks of carbon were made of this size by carbonizing slightly larger disks of compressed poly (vinylidene chloride) and smoothing them on each side by rubbing on fine emery paper. This made them flat, so that their thickness could be measured accurately. The disks were handled by dry-box technique to avoid adsorption of water or other contaminants from the air. 

Low polarisation ratios (<2 1) for absorption had also been found for amorphous PPV (1) deposited from solution by spin-coating on rubbed poly(tetrafluoroethylene) [PTFE]. It is evident that this could be improved on by making use of the high order parameter and self-organising properties of the nematic phase of liquid crystalline electroluminescent polymers such as those (16, 28 and 78-82) shown in Table 6.16. - 2 ° This was then found subsequently to be the case using thermotropic liquid crystalline polyfluorenes, such as 28 and 80 shown in Table 6.6 and segmented PPV derivatives, such as 81. The nematic phase exhibits the lowest viscosity of... 

Improved rubbing fastness can be achieved with partially hydrolysed poly vinylacetate (PVAc/PVA) or polyvinylether and the application of pigment binders, mostly based on acrylic copolymers similar to those nsed as hand builders (Chapter 4). Application methods mostly nse pad-dry techniqnes. 

Figure 7 (left) The electric field dependence of the time-ofiflight hole mobility for poly(9.9-dioctylfluorene) films. The open circles are data for a film prepared by spin coating. The filled circles are for a sample spin coated on a rubbed polyimide orientation layer, annealed in the nematic phase and then quenched to form a glassy film. 

Figure 8 shows the evolution of of a poly(butadiene-co-styrene) vulcanized rub-... 

Figure 13.7a shows a spechal image of the 5CB sample inserted between two germanium plates covered by a rubbed poly(vinyl alcohol) (PVA) alignment layer. 

Fibrillation - This phenomenon occurs when poly-tetrafluoroethylene fine powder particles are subjected to shear usually at above its transition point (19°C). For example, when fine powder particles rub against each other, groups of polymer chains are pulled out of crystallites. These fibrils can connect pol5mier particles together. They have a width of less than 50 nm. 

Yamamoto et a. [60-62] and Kurata et al [63] prepared polythiophene layers by vacuum evaporation. To ensure the deposition of poly- and not oligothiophenes, they removed low molecular weight material ( < 15-17) by Soxhlet extraction with CHCI3, The evaporated material is assumed to consist of poly-thiophene with a molecular weight of about 1500-2000 and 20-25 thiophene units. The X-ray and electron diffraction data of Yamamoto et al. point to a (partially) crystalline film with the polymer axes oriented perpendicular to a carbon or gold substrate plane if sub = 423 K. At lower substrate temperatures, the orientation and crystallinity are worse. This behaviour is not only true for the first deposited layer, but at least up to 10 layers, i.e, 100 nm. On polyimide substrates, however, the molecules lie on the substrate plane and orient along the rubbing direction of the polyimide [61]. 

The pol5mier of an alignment layer may be a poly(imide), which is spin-coated from solution. After drying, a film with a thickness of 0.1 jtt is formed at 200°C. This film is subsequently rubbed in one direction so that it functions as the alignment layer. 

The methods commonly used for chain alignment in polymer films have been reviewed [34]. They comprise the Langmuir-Blodgett technique, rubbing of the film surface, mechanical stretching of the film, and orientation on prealigned substrates. As an example, electroluminescence spectra of the oriented substituted poly(p-phenylene) presented in Chart 6.5 are shown in Fig. 6.9 a [35]. 

Hartmarm, L., Tremel, K., Uttiya, S., Crossland, E., Ludwigs, S., Kayunkid, N., Vergnat, C., Brinkmann, M., 2011.2D versus 3D crystalline order in thin films of regioregular poly(3-hexylthiophene) oriented by mechanical rubbing and epitaxy. Adv. Funct. Mater. 21,4047-4057. 

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