Thermo-optic properties, polymer

In this chapter we shall only be concerned with electro-optic and thermo-optic switching effects in thermotropic side-chain polymer liquid crystals. We will consider briefly the synthesis and structure of such compounds and show how the nematic, cholesteric and smectic phases arise. Since the optical properties of each of these phases are different, and may be altered depending on alignment within the phase, each gives rise to different electro-optic effects. If these are coupled to the use of dye additives or substituents, then it will be realized that a wide range of electro-optic devices based on dichroism or fluorescence as well as birefringence or scattering power may be fabricated. These will be considered and discussed in terms of their performance and potential applications. Finally, possible uses of polymer-low molar mass liquid crystal solutions will be considered in terms of electro-optic device applications. 

The potential to impart novel and enhanced properties to polymer materials without sacrificing the advantageous form-ability of the polymer matrix has fueled both academic and industrial interest in polymer nanocomposites during the past 20 years. For example, particle fillers are used to enhance thermo-mechanical properties or to engineer tailored electrical, optical, or transport properties of polymer thin films for applications ranging from electronic packaging to barrier and... 

The conformational mobility of a chromophoric main-chain polymer is often connected to its electronic structure. Therefore, changes in the UV-visible absorption spectra and/or chiroptical properties are spectroscopically observable as thermo-, solvato-, piezo-, or electrochromisms. It is widely reported that o-conjugating polysilanes exhibit these phenomena remarkably clearly.34 However, their structural origins were controversial until recently, since limited information was available on the correlation between the conformational properties of the main chain, electronic state, and (chir)optical characteristics. In 1996, we reported that in various polysilanes in tetrahydrofuran (THF) at 30°C, the main-chain peak intensity per silicon repeat unit, e (Si repeat unit)-1 dm3 cm-1, increases exponentially as the viscosity index, a, increases.41 Although conventional viscometric measurements often requires a wide range of low-dispersity molecular-weight polymer samples, a size exclusion chromatography (SEC) machine equipped with a viscometric detector can afford... 

This section will demonstrate the first sergeants and soldiers-type helix command surface experiment, in which thermo-driven chiroptical transfer and amplification in optically inactive polysilane film from grafted (or spin-coated) optically active helical polysilane onto quartz substrate [92]. Although helix and optical activity amplification phenomena based on the sergeants and soldiers principle was mainly investigated in polymer stereochemistry, the orientation and physical properties of a thick layer deposited onto a solid surface and controlled by a monolayer command film based on command surface principles was established in photochemical material and surface science [93,94]. Both sergeants and soldiers and command surface experiments appear to have been developed independently. 

Even a preliminary investigation of the properties of some inorganic pol5miers reveals that some of them have unexpected properties. Polythi-azyl is an anisotropic electrical conductor and shows conductivity that is comparable to metals. At 0.26 K this polymer becomes superconducting [4, 5]. Polysilanes which contain catenated silicon atoms in a polymeric chain have several unusual properties. These polymers have a o-electron delocalization. They are radiation sensitive and many of them are thermo-chromic. Many members of this family also show nonlinear optical behavior [17, 19]. 

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