Poly oriented films

BiaxiaHy oriented films have excellent tensile strength properties and good tear and impact properties. They are especially well regarded for their brilliance and clarity. Essentially all poly(ethylene terephthalate) film is biaxiaHy oriented, and more than 80% of polypropylene film is biaxiaHy oriented. Polystyrene film is oriented, and a lesser amount of polyethylene, polyamide, poly(vinyl chloride), and other polymers are so processed. Some of the specialty films, like polyimides (qv), are also oriented. 

In this review the definition of orientation and orientation functions or orientation averages will be considered in detail. This will be followed by a comprehensive account of the information which can be obtained by three spectroscopic techniques, infra-red and Raman spectroscopy and broad line nuclear magnetic resonance. The use of polarized fluorescence will not be discussed here, but is the subject of a contemporary review article by the author and J. H. Nobbs 1. The present review will be completed by consideration of the information which has been obtained on the development of molecular orientation in polyethylene terephthalate and poly(tetramethylene terephthalate) where there are also clearly defined changes in the conformation of the molecule. In this paper, particular attention will be given to the characterization of biaxially oriented films. Previous reviews of this subject have been given by the author and his colleagues, but have been concerned with discussion of results for uniaxially oriented systems only2,3). 

Aniline. Aniline black is a well known polymer of aniline formed by electrophilic additionf3.41. Numerous investigators have formed poly(aniline) films by anodic deposition of Pt and other electrode materials. We have examined the interaction of aniline with clean Ni(lll) and Ni(100) surfaces in ultrahigh vacuum and found aniline to form an orientationally ordered, thermally stable polymer film. Electrochemically prepared poly(aniline) films also show the high degree of orientational ordering. 

The AES results indicate that the aniline coverage is more than two times greater than the maximum coverage based on van der Waals radii. The TPR results show this species is too stable to be a condensed multilayer. Hence, we conclude that aniline polymerized forming a very stable polymer layer. In addition, the absence of infrared bands corresponding to C=C stretches or ring vibrations indicated that the poly(aniline) film was formed with the phenyl rings parallel to surface. The infrared results also indicated that the poly(aniline) film had N-H bonds which were oriented perpendicular relative to the surface. 

N Tanigaki, K Yase, and A Kaito, Oriented films of poly(p-phenylene) by friction-deposition and oriented growth in polymerization, Mol. Cryst. Liq. Cryst., 267 335-340, 1995. 

Konaga,T., Fukada,E. Piezoelectric effect in oriented films of poly-y-benzyl L-glutamate. Rep. Progr. Polymer Phys. Japan 13, 379 (1970). 

The arrangement of helices in the solid and liquid crystalline states of poly(a-phenylethyl isocyanide) were determined by X-ray and electron diffraction. Well-defined diffraction patterns were obtained from oriented films using selected area electron diffraction. Intermolecular and intramolecular patterns were calculated from the five Debye-Scherrer rings. All the reflections were indexed in terms of a pseudo-hexagonal triclinic unit cell, with... 

Since many of the aromatic polymers studied [e.g., poly(n-hexylphenylsilane)] are also quite rigid in solution and optical microscopy studies on concentrated solutions often show signs of long range order, a partially oriented sample of this material was prepared by shear flow extension. Third harmonic measurements at 1.064 /im on partially oriented films prepared in this... 

The matter has been carried further in the studies of Gratzer et al. (1961) with measurements of the absorption of polarized radiation by oriented films of a-helical polypeptides. Their polarization spectra of poly-L-ala-nine, and of poly-7-methyl-L-glutamate (Fig. 8) clearly show the predicted opposite polarization for the two peptide absorption bands of the -helix. Taking these band positions as 1910 and 2060 A, we obtain a band separation of 3800 cm . [The value of 2700 cm in the paper of Gratzer et al. 

In this section, the most important structural (grain size, grain orientation and intragrain defects) and electrical properties of the poly-Si films prepared by the ALILE process are discussed. 

A typical EBSD map of the surface of a poly-Si film on glass prepared by the ALILE process is shown in Fig. 12.9 (left) [39]. The sample was annealed at 425°C for 16h. Afterwards, the Al(+Si) top layer was removed by CMP. The poly-Si film shown here features an average grain size of 7 pm and a maximum grain size of 18 pm. From such EBSD measurements, not only the grain size but also the crystallographic orientation of the grains can be determined. 

A high preferential (100) orientation of the poly-Si surface is favorable for subsequent epitaxial growth at low temperatures [41-43]. Due to the preferential (100) orientation, the utilization of the poly-Si films formed by the ALILE process as a template (seed layer) for subsequent epitaxial thickening at low temperatures is quite attractive [44]. 

In addition to the experiments with very thin barrier layers, rather thick barrier layers have also been investigated [51]. The thick barrier layers were formed by thermal oxidation of the Al surface (e.g., for 2h at 560°C). With such a thick barrier layer, an estimated average grain size of above 200 pm was reached. But at the corresponding Ta of 450°C, it took days to form a continuous poly-Si film. The influence of a barrier layer formed by thermal oxidation on the preferential orientation of the poly-Si surface was already described (see Fig. 12.10). 

Koenig, J. L.. Wolfram, L., Grasselli. J. Structure and properties of oriented poly(acylonitrile) films. Polymer Preprints. 10, 959 (1969). 

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