Optical materials, nonlinear obtain

We first discuss the materials research which includes monomer synthesis, growth of monomer crystalline structures and polymerization in the solid state, yielding the requisite polymer structures. Next, the nonlinear optical experimental research is discussed which includes a novel experimental technique to measure x (w). Linear and nonlinear optical data obtained for the polydiacetylene films is subsequently presented. Detailed theoretical analysis relating the data to x (< >) and subsequently to its molecular basis will be discussed in a later publication. 

Reorientation dynamics of molecular tracers in polymers is not only important for the understanding of slow relaxation phenomena in glassy polymers but plays also a critical role in practical problems such as molecular design of nonlinear optical materials with long-term stability based on dyes/polymers complexes. We show here the reorientation dynamics of molecular tracers in glassy polymers obtained by the armealing-after-irradiation method described below. These experimental results are compared to the local relaxation processes of glassy polymers obtained by the already established measurement techniques such as dielectric relaxation and solid state NMR. Finally, the molecular interpretation of the relaxation of free-volume distribution in polymers will be discussed. 

The increasing interest in obtaining efficient organic optically nonlinear materials resulted in a combinational chemistry approach to their synthesis. The structures of several nitroaniline derivatives (including five Schiff bases), the compounds which belong to a chemical class having potential application as nonlinear optical materials, have been reported4,5. 

Side-chain liquid-crystalline polymers with controlled molecular weights have been obtained by the polymerization of FM-25 with 1-22 (X = Br)/CuBr/ L-3 in the bulk at 100 °C, to examine the thermotropic transition as a function of the MWD.324 Second-order nonlinear optical materials with branched structure were prepared by the copper-catalyzed radical polymerization of FM-26 and FM-27 using hyperbranched poly[4-(chloromethyl)styrene] as a multifunctional initiator.325... 

A similar iodonium exchange reaction involves aryl(cyano)iodonium triflates 278 and stannylated aromatic precursors providing many kinds of diaryl or aryl(heteroaryl) iodonium salts [145,147,401], Tykwinski, Hinkle and coworkers have reported an application of such iodonium transfer reaction for obtaining of a series of mono- and bithienyl(aryl)iodonium triflates 279 with increasingly electron-withdrawing substituents on the aryl moiety (Scheme 2.81) [401], Thienyl and bithienyl iodonium salts prepared by iodonium transfer reaction using PhI(CN)OTf are potentially useful as nonlinear optical materials [402],... 

Organic compounds with delocalized jr-electron systems, e,g., jr-conjugated polymers, are considered to be candidates for third-order nonlinear optical materials. Among them, polydiacetylenes (PDAs) are an important class of conjugated polymers that has attracted investigators from many different fields (7,2). PDAs, which can be obtained as single crystals by topochemical solid-state polymerization (5), have been extensively studied since 1976 (4). PDAs show large third-order nonlinear optical susceptibilities (5) and ultrafast optical... 

Considerably higher efficiences (ot about 15 percent) are now obtainable with the new nonlinear optical material barium-3 borate (BBO). Besides the high conversion efficiency this material generates the second harmonic of radiation at wavelengths as short as 410 nm. Therefore not only the 4p-5p 5/2,2 transition can be used for the two-photon resonant enhancement of but also the resonances 4p-5p... 

In the field of the synthesis of molecule-based second order nonlinear optical materials, the self assembly approach has attracted much attention in recent years because it leads to obtain functional and structurally stable molecular films, as a consequence of the intrinsic versatility of molecular chemistry and mild deposition conditions possible [75, 137, 138], Although the most detailed investigations of self-assembly have focused on long chain alkanethiol and alkyl-silane derivatives, the potential for formation of relatively ordered, densely packed arrays of electronically functional molecules is of great scientific interest the chance to modify surfaces with self-assembled layers terminated with reactive... 

A diagrannnatic approach that can unify the theory underlymg these many spectroscopies is presented. The most complete theoretical treatment is achieved by applying statistical quantum mechanics in the fonn of the time evolution of the light/matter density operator. (It is recoimnended that anyone interested in advanced study of this topic should familiarize themselves with density operator fonnalism [8, 9, 10, H and f2]. Most books on nonlinear optics [13,14, f5,16 and 17] and nonlinear optical spectroscopy [18,19] treat this in much detail.) Once the density operator is known at any time and position within a material, its matrix in the eigenstate basis set of the constituents (usually molecules) can be detennined. The ensemble averaged electrical polarization, P, is then obtained—tlie centrepiece of all spectroscopies based on the electric component of the EM field. 

Theoretical estimations and experimental investigations tirmly established (J ) that large electron delocalization is a perequisite for large values of the nonlinear optical coefficients and this can be met with the ir-electrons in conjugated molecules and polymers where also charge asymmetry can be adequately introduced in order to obtain non-centrosymmetric structures. Since the electronic density distribution of these systems seems to be easily modified by their interaction with the molecular vibrations we anticipate that these materials may possess large piezoelectric, pyroelectric and photoacoustic coefficients. 

Oligomerization and polymerization of terminal alkynes may provide materials with interesting conductivity and (nonlinear) optical properties. Phenylacetylene and 4-ethynyltoluene were polymerized in water/methanol homogeneous solutions and in water/chloroform biphasic systems using [RhCl(CO)(TPPTS)2] and [IrCl(CO)(TPPTS)2] as catalysts [37], The complexes themselves were rather inefficient, however, the catalytic activity could be substantially increased by addition of MesNO in order to remove the carbonyl ligand from the coordination sphere of the metals. The polymers obtained had an average molecular mass of = 3150-16300. The rhodium catalyst worked at room temperature providing polymers with cis-transoid structure, while [IrCl(CO)(TPPTS)2] required 80 °C and led to the formation of frani -polymers. 

If the mesogens are pendant to the polymer backbone, materials are obtained with special magnetic, electrical and optical properties. They provide for nonlinear optics (NLOs) applications in numerous optoelectronic elements. 

Lee and co-workers reported an interesting example of a conjugated polymer obtained by polymerizing 5-phenyl-2-(propynylamino)-4(57/)-oxazolone in the presence of palladium or platinum chlorides. The authors predict this unique material may have applications for polymer electrolytes, semiconductors, and nonlinear optical (NLO) materials. 

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