Molecules, hairy rod

Fig. 29 Self-assembly of hairy-rod molecules. From left to right the interfacial tension becomes relatively more important compared to the elastic stretching of the side chains [225]...

Fig. 13 Above Schematics of a hairy-rod polymer consisting of a stiff backbone and flexible covalently connected side chains. N, Zk, and v are the number of segments, the segment length (the Kuhn length), and the volume of the beds of the side chains, respectively M, Zu, L, and d are the number of the repeat units, distance between grafting points (the unit length) and the length and diameter of the rod, respectively. Below. End-on schematics of (a) nematic (Nem) and (b) hexagonal (Hex) phase of hairy-rod molecules. Adapted from [24]...

The data correlate with a sanidic layer structure as sketched in Figure 5. Similar orientation in the bulk phase has been observed for other so-called hairy-rod molecules with solubilizing side groups like polyesters and polyphenylenes [22 - 24]. 

Molecular composites from hairy-rod molecules prepared via the Langmuir-Blodgett technique [71]... 

Sekkat et al. 93 have investigated the photobehavior under polarized light of spin-coated films obtained from a hairy-rod poly(L-glutamate) with azobenzene in the side chains (Scheme 11, compound XIX). It is known 96,971 that, in the presence of a linearly polarized pump light beam, azo molecules experience a cycle of photoisomerization reactions and align themselves perpendicularly to the pump beam polarization direction. For the above polypeptide it was shown that, in the trans cis photoisomerization cycle, the created cis state is aligned perpendicularly to the polarization of the pump beam. 95 ... 

One of the guiding principles underlying much of the physics in conventional polymers is that many macroscopic macromolecular properties, not least the structure formation, can be satisfactorily understood even when the details of single molecules are ignored [11]. As is discussed later in this review, this idea still remains relevant for the intermolecular self-organization of hairy-rod PFs and for their macroscopic alignment. However, much of the behavior seen in PFs (and virtually all other electronic polymers as well) is an excep-... 

For optical data storage, photosensitive hairy rod LBK structures can be constructed by incorporating photochromic molecules in the side chains [53-55]. The azobenzene molecules undergo transcis photoisomerization under irradiation of photoactive light with an appropriate wavelength, as detailed in the second section of this paper. This photochemical reaction has been shown to alter the structural properties of hairy rod LBK films, which have been investigated by using FT-IR and UV-VIS spectroscopies and X-ray reflectometry [54]. 

The liquid-like nature of the matrix in hairy-rod multilayer assemblies suggests that they can be used as hosts for various types of guest molecules which, by themselves, cannot be processed into mono- or multilayer form. In fact, a wide variety of oleophilic dyes can be cospread with PG or IPC onto the air-water interface [84,88]. LB assemblies are then built up as usual. Form-anisotropic dye molecules like /3-carotene or azo dyes are incorporated into the host matrix with a preferential orientation of their molecular long axis parallel to the director axis of the HRM backbone. The resulting architecture is schematically depicted in Figure 9.6. 

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