Liquid crystalline polymers films from

F. 2.13 Left the chemical stmctures and a schematic representation of desorption and adsorption of 9 in the nanoporous columnar liquid crystalline polymer film. Right the X-ray diffraction of the erosslinked network at different stages of adsorption and desorption. Adapted with the permission from Ref. [66]. Cop5uight 2006 American Chemical Society and Ref [64]... 

Fig. 5.13 Photomechanical effects. Schematic illustration of UV-light-induced bending of a cross-linked liquid-crystalline polymer film containing azobenzene groups. Light is absorbed at the upper surface layer of the film and causes anisotropic contraction. Adapted from Ikeda et al. [51] with permission from Wiley-VCH.

Thin polymer films may also be investigated by TEM and high resolution images are obtained for e.g. thin films of liquid crystalline polymers [64]. Usually thin microtome cuts from bulk samples are investigated, but also epitaxial growth of polyoxymethylene on NaCl [152], chain folding of polyethylene crystals [153], epitaxial crystallization of polypropylene on polystyrene [154] or monomolecular polystyrene particles [155] are observed. The resolution is, however, in most cases not comparable to STM. 

The development is reviewed of liquid-crystalline polymers whose mesophase formation derives from the nature of the chemical units in the main chain. The emphasis lies primarily on highly aromatic condensation polymers and their applications. The general properties of nematic phases formed by such polymers are surveyed and some chemical structures capable of producing nematic phases are classified in relation to their ability to form lyotropic and thermotropic systems. The synthesis, properties, physical structure and applications of two of the most important lyotropic systems and of a range of potentially important thermotropic polymers are discussed with particular reference to the production and use of fibres, films and anisotropic mouldings. 

In order for the polymer films not to scatter light excessively, it was necessary to make the measurements on unoriented films of the non-liquid crystalline polymers. The films were cast from filtered nmp solutions onto 1/16 " thick quartz plates. 

The objective of this work has been to generate films, tapes or ribbons which might serve as a prepreg from blends of either an Ultem or a PEEK or a high molecular weight PPS with various liquid crystalline polymers, to identify the parameters that control the formation of reinforcing microfibrils of LCP phase, and to study the mechanical properties of the composite films. 

The principle of using side chain liquid crystalline polymers as optical storage systems has been estabhshed. This has been demonstrated using a polymer film prepared from a side-chain polymer showing nematic hquid crystalline characteristics with the structure... 

Han et al., also studied exposure of films of liquid crystalline polymers with azobenzene side chains to linearly polarized light of 436 nm that results in successive occurrences of uniaxial in-plane orientations, followed by out-of-plane orientations of azobenzenes. Two kinds of orientation modes were observed. These are possibly extreme cases, when linearly polarized light with the electric vector parallel to the xz-plane comes along the z-direction. One is the uniaxial in-plane orientation of the azobenzene with a dipole moment parallel to the x-axis from the x- to y-direction and the other is out-of-plane... 

High modulus fibers and films are produced from extended chain crystals in both conventional polymers, notably PE, and liquid crystalline polymers. Carter and Schenk [18], Jaffe and Jones [19], and Zachariades and Porter [20] have reviewed the topic of high modulus organic... 

The intensity of the electron beam used to examine thin crystalline polymer films by electron microscopy is usually of sufficient intensity to induce cross-linking. It is not surprising, therefore, after initial examination in the crystalline state, that thin films of poly(amides) and polyethylene display ordered structures when subsequently examined in the molten state by this technique. These observations are to be expected. They cannot be construed as evidence that, in general, the liquid state in polymers is an ordered one.(33) The partially ordered liquid represents an interesting, unique situation that results from the nature of the chain arrangement at the time of network formation. 

High modulus fibers and films are produced from extended chain crystals in both conventional polymers, notably PE, and liquid crystalline polymers. Carter and Schenk [18], Jaffe and Jones [19] and Zachariades and Porter [20] have reviewed the topic of high modulus organic fibers, fully describing their preparation, structure and properties. High modulus fibers are found in such critical applications as fiber reinforced composites for aerospace and military applications and industrial fibers such as belts and tire cords. Extended chain crystals can also form when polymers are crystallized very slowly near the melting temperature but they are weak and brittle. 

---