Non linear optical polymers

As stated above, for a molecnle to demonstrate bnlk second order properties it is necessary for the dipole of all the molecnles to lie in the same direction. This situation is very difficnlt to attain in small molecnles where the tendency is for the molecules to crystallise with their dipoles opposing each other. This fact has led to a switch of interest to polymers that incorporate the small NLO molecnle. 

Using polymers allows the dipoles to be aligned by two methods  

As in many other applications, having the effect contained in polymeric materials carries several advantages  

Several polymeric confignrations have been examined for the production of NLO polymers, but the two basic approaches are  

The dominant methodology is that based on covalent bonding of the chromophore to the polymer, as this shows much improved long term stability over simple guest-host systems. Guest-host polymers using NLO guests have been extensively studied in the area of photorefractive polymers (see section 5.6.3). 

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Fig. 3.24 Examples of non-linear optical polymers with (a) pendent, (b) semi-buried and (c) backbone chromophores...

Kim DY, Tripathy SK, Li L, Kumar J. 1995. Laser induced holographic surface relief gratings on non linear optical polymer films. Appl Phys Lett 66 1166 1169. 

New Engineering Thermoplastics New High Performance Thermosets Thermotropic Liquid Crystals Lyotropic Liquid Crystals Molecular Composites Advanced Composites Non-Linear Optical Polymers Electronically Conducting Polymers... 

The application tests of hyperbranched polymers have namely focused on their employment as non-linear optical polymers, polymer electrolytes, biomaterials, supramolecular components (nanomaterials), photolithographic materials, coatings, modifiers and additives and polymeric membranes so far [3]. 

Ahlheim M, Lehr F (1994) ElectroopticaHy active polymers. Non-linear optical polymers prepared from maleic anhydride copolymers by polymer analogous reactions. Macromol Chem Phys 195 361 373... 

In recent years, research on polymer-metal nanoeomposites and their properties has attracted considerable attention due to their potential applications in catalysts, electronics and non-linear optics. Polymer-metal composites consist of polymer and metal particles on the surface or interior (core) of the polymer matrix." They exhibit various properties depending on the type of metal and polymer, especially the former. These composites not only combine the advantageous properties of polymers and metals but also exhibit many new characteristics that single-phase materials do not have. Precious metals such as silver and gold have been studied most extensively among polymer-metal nanoeomposites." Many polymer-metal nanoeomposites have been prepared in one step with y-irradiation in an aqueous solution. Choi et al. reported on polyester-silver and nylon-silver nanoeomposites prepared by the dispersion of silver nanoparticles, which were prepared by y-irradiation, on to polyester and nylon during condensation polymerization to obtain antibacterial fibers." It was found that the silver nanoparticles aggregated in the polyester matrix, whereas the silver nanoparticles dramatically dispersed in the nylon matrix. 

A.J. Hceger, D. Moses, M. Sinclair, Semiconducting polymers fast response non-linear optical materials, Synth. Met., 1986. 15, 95. 

Wudl F, Ikenoue Y, Patil AO in Ulrich D, Prassad PN (eds) Non-linear Optical and Electroactive Polymers, Plenum Press, New York, in press... 

A rapidly increasing number of publications on polysilanes documents current interest in these polymers (JJ. Polysilanes are potentially applicable in microlithography as high resolution UV-resists (2J, imageable etch barriers ), or contrast enhancement layers (4). They have been successfully used as precursors to Si-C fibers (5J and ceramic reinforcing agents ((L). Polysilanes have also initiated polymerization of vinyl monomers (J ). Doping of polysilanes have increased their conductivity to the level of semiconductors (8). Very recently polysilanes were used as photoconductors (9) and non-linear optical materials (10b... 

F Wudl, P-M Allemand, G Srdanov, Z Ni, and D McBranch, Polymers and an unusual molecular crystal with NLO properties, in Materials for Non-Linear Optics Chemical Perspectives, S.R. Marder, J.E. Sohn, and G.D. Stucky, Eds., American Chemical Society, Washington, 1991, pp. 683-686. 

H.S. Nalwa and S. Miyata, Non-linear Optics of Organic Molecules and Polymers, CRC Press, Boca Raton, FL, 1997. 

Multiple Heck reactions have also been applied in a number of ways to prepare polymers (Scheme 40). One-dimensionally 7r-conjugated polymers are attractive materials because of their optical and electrical properties resulting from 7r-electron delocalization along their main chains. Among these, poly(p-phenylenevinylene) (PPV) shows high electrical conductivity, large non-linear optical responses, and electroluminescent activity. One approach... 

Non-linear optical effects were observed for the 551 polymer-encased gold particles... 

Crosslinked LC elastomers (Figure 19d) are very promising for piezoelectric and ferroelectric applications, and also as non-linear optic materials. The first synthetic step to such materials is the preparation of usual side chain or combined LC copolymers doped with a small part of side chains containing a polymerizable >C=C< double bond at the end (Figure 23 shows a particular example of a crosslinkable LC polymer64). The copolymer can be further photocrosslinked, giving an elastic polymer film which reveals... 

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