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Second‐order optical nonlinearity exists in a noncentrosymmetric crystal. We investigated a new molecular concept for noncentrosymmetric crystal structure. The Λ‐shaped molecules have been found to easily form noncentrosymmetric crystals by stacking along one direction. The configuration of Λ‐shaped molecules is close to an optimum condition for crystal phase‐matched nonlinearity. We demonstrate that methanediamine derivatives forming Λ‐shaped conformation are promising as efficient χ(2) materials.

The synthesis and characterization of poly(ethylene oxide)-b-poly(4-butyltriphenylamine)-b-(polyethylene oxide) triblock copolymers (PEO-b-PBTPA-b-PEO) with different block ratio are described. The optical properties of block copolymers were investigated by UV-vis absorption, and photoluminescence (PL) spectroscopy. From atomic force microscopy (AFM) observation of the annealed thin films of block copolymers, microphase-separated morphology was observed.

The electric field induced dynamic phase-matching of SHG waveguide was first demonstrated using a main chain type NLO polymer. The optimum phase-matching thickness was controlled by applied an electric field to polymer waveguide. The effective phase-matching thickness variation induced by poling is about 0.025 micrometers which is 6 times larger than FWHM of phase-matching thickness in conventional slab waveguide. The efficient phase-matched SHG was observed from taperless slab waveguide. No decay of SH conversion efficiency is observed in the presence of electric field.

The quadratic nonlinear optical (NLO) properties of aliphatic polyester/p-nitroaniline (p-NA) systems have been studied. Even without applying an electric field, the composite films show the second harmonic generation (SHG). The SHG activities depended on the ratio of CH2 and 000 groups in the polymer. ( ranging from 80 to 130 times larger than that of urea at CH2/C00 = 4-6.) Especially, poly(buthylenesebacate) (PBSe)/p-NA systems exhibited the largest values (130 times larger than that of urea). The SHG active systems were found to have a new phase as demonstrated by differential scanning calorimetry (DSC) technique.

In recent years, there has been a growth of interest in organic materials for applications in the field of nonlinear optics!'2 Materials possessing both large second-order nonlinear susceptibilities and bulk crystallinity are important for highly efficient frequency conversion. Organic molecular compounds are quite promising for achieving such high conversions because their second-order nonlinearity can be enhanced by extended conjugation and by the presence of spectroscopic charge-transfer arising from electron-donating and electron-accepting substituents on an aromatic ring or a similar conjugated system. Crystallographically, for quadratic nonlinearity the crystal unit cell must lack a center of symmetry. 4-Nitroaniline is one of the simplest organic compounds having an electron donor group and an electron acceptor group at the para positions. It has large molecular hyperpolarizabilityβ, but does not show second-order nonlinear optical effects because of the centrosymmetry of the crystal. Therefore, in order to achieve noncentrosymmetric structure, large nonlinear susceptibility and transparency, we have modified 4-nitroaniline system. A new organic nonlinear optical material N-methoxymethy1-4-nitroaniline(MMNA) was synthesized. Second-harmonic generation(SHG) measurements performed in powder form shows high second-order optical nonlinearity. This has also been confirmed by the observation of efficient phase-matched SHG from the single crystal. In this article we report the details of synthesis, crystal growth, crystal structure, phase-matching behavior, and effective bulk nonlinearity of MMNA crystal.

The oligomerization of some tertiary aromatic amines was studied using ferric chloride in a variety of solvent. The predominant dimer formation of triphenylamine (TPA) was observed in chloroform at 0 °C where concentration of TPA was 0.125 mmol/l and the molar ratio of ferric chloride to TPA was 4. Except for N-methyldiphenylamine, high molecular weight oligomers were formed in a variety of solvents.

We report luminescence study of intramolecular exciplexes based on an aminobenzanthrone derivative, dimethyl-amino-N-acetyl-3-aminobenzanthrone (BDA). The BDA compound shows strong dependence of the exciplex emission band intensity on the solvent dielectric function and moderate dependence on its viscosity. The exciplex emission mechanism is discussed in view of the unusual solvent polarity dependence and solvent-dependent excited state lifetimes. Preliminary results on single-molecule detection in polymer films are also presented.

We report a study of excimer emission from copolymers of dibutylfluorene and butylphenylphenoxazine. Temperature dependence of photoluminescence (PL) spectra measured from room temperature to above glass transition temperature, and excitation power dependence of PL spectra reveal that the observed differences in excimer intensity between PL and electroluminescence spectra are neither solely due to local heating by electric current nor to differences in exciton density. Instead, different nature of the excitations upon photoexcitation and excitation by passing current has to be considered to explain the different behavior.

Summary form only given. It is well known that fluorenone derivatives have good electron transport ability due to low LUMO. However, low molecular weight compounds have poor mechanical properties and they easily crystallize and decrease the electron transport ability. We have prepared a new polymer having fluorenone units on the side chain- poly(4-vinylbenzyl 9-dicyanomethylenefluorene-4-carboxylate) and measured electrical porperties. The momomer was prepared from 9-dicyanomethylenefluorene-4-carboxylic acid and p-chloromethyl styene, and was polymerized by conventional radical polymerization in solution. Polymer was obtained with 61% yield and as a yellow powder. The polymer was soluble in organic solvent such as THF, chloroform and methylchloride. The number average molecular weight was determined to be 8,200 by GPC using a calibration curve of standard polystylene. The structures of the resulting polymer were confirmed by /sup 1/H-, /sup 13/C-NMR and IR spectra. Polymer in THF solution showed a UV absorption maximum(/spl lambda/max) at 351.25nm. The polymer film showed two reversible redox potentials at -0.51V,-1.04V(oxidation) and -0.62V,-1.15V(reduction). Further detailed studies will be presented at the poster session.

Preparation de copolymeres de composition et de masse moleculaire differentes. Utilisation d'un melange CH 2 Cl 2 -CH 3 (n) pour eluant et d'un gel de polystyrene comme phase stationnaire. Etude de l'influence de la masse moleculaire des copolymeres sur la separation: elargissement des pics par diminution de la masse moleculaire. Temps de retention augmentant avec la teneur en styrene

1H and 13C NMR spectra of 1,5-cyclooctadiene oligomers were investigated and compared with those of 1,4-polybutadiene. The oligomers were prepared with Rh2O7 as catalyst and fractionated by vacuum distillation or gel-permeation chromatography. It was found that each fraction consists of a mixture of steric isomers possessing cis and trans structures in different ratios. The 13C NMR spectra of oligomers with less than 24 carbons vary with ring size, which is explained in terms of ring strain effects. The 13C NMR spectra of oligomers with more than 28 carbons are identical with the spectrum of 1,4-polybutadiene. It resulted that the ratio of cis to trans structure in the oligomers decreases with increasing molecular weight from 70:30 (C16) to that in the cyclooctadiene polymer (40:60).

Rates of Quenching and Hydrogen Abstraction of Benzophenone Triplet with Cumene and Oligostyrenes

Distribution de sequence des trois unites isomere cis-1,4, trans-1,4 et 1,2 d'oligomeres prepares par voie anionique, radicalaire ou avec un amorceur au cobalt

The spin-decoupled 1H NMR and 13C NMR methods were employed for the determination of the cis-trans sequence distribution in polybutadiene. Poly(butadiene-2,3-d2) and cis-trans isomerized polybutadienes were used for the peak assignment and the resonance of methylene protons in cis-trans linkage could be described as an A1B2 system. The dyad and triad sequence distributions of cis-1,4 and trans-1,4 units were determined for isomerized, equibinary, and lithium catalyzed polybutadienes, and polycyclooctadienes. The accuracy of the measurements was also studied comparing the results with those by infrared method.

Spectres des paraffines cycliques C 24 H 48 , C 28 H 56 , C 32 H 64 , C 36 H 72 , C 40 H 80 , C 48 H 96 , C 64 H 128 et C 80 H 160 , des paraffines normales C 19 H 40 , C 22 H 46 et C 32 H 66 et de polyethylene cristallin

Temperature-dependent measurements have been made on the proton NMR relaxations and proton linewidths of the cyclic paraffins (c-C24H48, c-C28H56, and c-C128H256) in the solid state. It is found that in c-C24H48 and c-C128H256 there exist two transitions, one due to the melting process and the other due to a rapid transition between trans and gauche conformers in a compact structure that consists of two parallel trans zigzag straight chains bridged at both ends in the crystalline state. In c-C28H56 there exists only the transition due to melting. Proton NMR relaxations have also been measured for c-C40H80 and c-C160H320 at room temperature, in addition to those for c-C24H48, c-C28H56, and c-C128H256. It is found that the extent of molecular motion decreases as the chain length increases.

A study was made on the isomeric structure of trimethyl-cyclododecatriene (TMCDT) prepared by oligomerization of isoprene with (C5H8)2Mg–AlCl3–TiCl4–CH3SCH3 as a catalyst. The 1H and 13C NMR spectra of this compound showed the presence of one cis and two trans double bonds. The partial ozonolysis of TMCDT followed by the reductive degradation to alcohols gave three products corresponding to a linear trimer and two dimers of isoprene. These products were fractionated by liquid chromatography. 13C NMR measurements showed these partial ozonolysis products to be 5-methyl-cis-5-decene-2,9-diol, 5-methyl-transs-4-nonene-1,8-diol, and 5,8-dimethyl-trans-cis-4,8-tridecadiene-1,12-diol, indicating that one of the trans isoprene units was linked to the other isoprene units in a head-to-head and tail-to-tail fashion. This was also confirmed by an infrared measurement of hydrogenated TMCDT. The TMCDT was concluded to be 1,5,9-trimethyl-cis-trans-trans-cyclododecatriene.

The cycloparaffins (CH2)36 and (CH2)60 were crystallized epitaxially from solutions on the (001) face of the NaCl crystal at various temperatures. Two types of crystals, so-called edge-on and flat-on crystals, were separately obtained depending on crystallization temperature. The temperature for obtaining edge-on crystals was higher by ca. 10°C than that for flat-on crystals. In both flat-on and edge-on crystals, the long side (b-axis) is aligned to the 〈110〉 direction of NaCl. The (001) plane in the flat-on crystal and (202) in the edge-on crystal are parallel to the substrate surface. The direction of the vector c′ defined as −a + c is parallel to the molecular axis in monoclinic cycloparaffin crystals. The angle β′ between c′ and the a-axis is almost constant at about 119°, while c′ changes linearly with the number of carbon atoms in a molecule. The space group changes from Aa to Ia in the new unit cell with the dimensions a, b, c′ and β′.

Isoprene can be polymerized into four types of isomeric structures; cis-1,4, trans-1,4, 3,4, and 1,2, depending on catalysts and polymerization conditions. So far, the difference of mechanical and thermal properties among polyisoprenes has been discussed chiefly on the basis of amounts of these isomeric structures. However, it is quite reasonable to expect that the polymer properties are affected not only by the composition of isomeric structures but also by the distribution of isomeric structures, the arrangement of head and tail linkages, and the degree of branching. This idea was adopted by Hackathorn and Brock as an explanation of the poor crystallizability of lithium polyisoprene; i.e. head-to-head and/or tail-to-tail linkages of 1,4- and 3,4-units prevented the crystallization of the polymer. Pyrolysis-gas chromatography has been applied to the investigation of the sequence distribution of 1,4- and 3,4-units in polyisoprenes. This method is based on the structural relationship between the isoprene dimers and the diad sequences of 1,4- and 3,4-units. However, it is difficult to discuss the slight differences in the yield of each dimer because the absolute amount of the dimers is small (∼30%) compared to the isoprene monomer (∼65%). Ozonolysis has been used to measure the amount of head-to-head, head-to-tail, and tail-to-tail linkages of the 1,4-unit in polyisoprenes. This method, however, is limited to the detection of these linkages of 1,4-units. In a previous paper, we have investigated 13C NMR spectra of chicle and cis-trans isomerized polyisoprenes and determined the sequence distribution of cis-1,4- and trans- 1,4-units in these polymers. We have also studied 13C NMR spectra of hydrogenated polyisoprenes prepared with n-BuLi-Et2O catalysts and found that 1,4- and 3,4-units were distributed randomly along the polymer chains regardless of the amounts of 3,4-units. In the present investigation we prepared various types of polyisoprenes and discussed the distribution of 1,4-and 3,4-units, arrangements of head and tail linkages, the branches of polymer chains, and the tacticity of polyads of 3,4-unit by the use of 13C NMR spectra of hydrogenated polyisoprenes.

Poly(methyl methacrylate) (PMMA) was separated by stereoisomerism using high performance liquid chromatography (HPLC). Using a cross-linked polyacrylonitrile gel as the stationary phase and a mixture of dichloromethane and n-hexane, ethyl ether, or benzene as the eluent, isotactic PMMA eluted faster than syndiotactic PMMA. With a cross-linked polystyrene gel and a mixture of dichloromethane and nitromethane, syndiotactic PMMA eluted earlier. With some eluent forming stereocomplex of PMMA after injecting a mixture of isotactic and syndiotactic polymers, the sample did not elute or eluted at a different elution time from that expected from an experiment of a separate injection. From the cloud point it was found that the separation was done by an adsorption mechanism rather than phase separation.

NMR Measurement of Identical Polymer Samples by Round Robin Method I. Reliability of Chemical Shift and Signal Intensity Measurements

High-resolution 13C nuclear magnetic resonance (n.m.r.) spectra of melt-quenched polyethylene and polyethylene single crystals are measured by the cross-polarization/magic angle spinning technique. Melt-quenched polyethylene and polyethylene single crystals have four small upfield peaks, a shoulder on the main peak and three small peaks, respectively. Based on the 13C n.m.r. resonance lines of cyclic paraffin C64H128 reported previously, it is concluded that the main peak and the three upfield peaks arise from the trans zigzag structure region and the folded structure region, respectively. From these peak intensities, it is estimated that the stem length of polyethylene single crystals is approximately 125 A. Taking into account an error in the estimation of the small peak intensities, the calculated stem length of 125 A is consistent with the crystal thickness (120–150 A) observed directly by electron microscopy. It can be concluded, therefore, that polyethylene single crystals mainly contain sharply folded structure. Melt-quenched polyethylene may contain sharply folded structure to some extent in addition to loose loops.

High-resolution 13C NMR spectra of cyclic paraffins, n-paraffins and polyethylene in the solid state have been measured by the cross polarization—magic angle spinning technique. It is shown that the 13C chemical shift of the main peak for the trans-zigzag inner methylene carbons of paraffins with the orthorhombic form appears at about 1 ppm further upfield than that with the triclinic form. This difference was theoretically verified to be caused by a local difference in intermolecular interactions in the orthorhombic nad triclinic forms, based on the tight-binding molecular orbital calculation within the CNDO/2 framework.

Stearyl methacrylate (SMA) was copolymerized with ethylene dimethacrylate (EDMA) in ratios of 1:4 to 4:1 by conventional suspension polymerization in w

Le SBR prepare par voie radicalaire peut etre separe suivant sa teneur en unites monomeriques styrene par HPLC, a l'aide d'un gel d'acrylonitrile reticule comme phase stationnaire, avec le melange hexane-chloroforme

The chemical structure of naturally occurring cis-polyisoprene isolated from Solidago altissima was determined by 13C NMR spectroscopy. The alignment of the isoprene units in the polymer was estimated to be in the order: dimethylallyl terminal unit, three trans units, about 1000 to 2200 of internal cis units, and a cis allyl alcohol terminal unit. This demonstrates that the biosynthesis of cis-polyisoprene in this higher plant starts from trans,trans,trans-geranylgeranyl pyrophosphate.

1H NMR spectra of polyisoprene were assigned using polymers of isoprene-1,1,4,4-d4, isoprene-1,1,5,5,5-d5, and isoprene-4,4-d2 polymerized with various catalysts. The methylene-proton signal at 2.1 ppm in cis-1,4- and trans-1,4-polyisoprenes was divided into H4- and H1-proton signals; H4 resonated at 2.21 ppm in both cis-1,4 and trans-1,4 units, whereas H1 resonated at 2.05, 2.21, and 2.15 ppm. Splitting due to the dyad sequences of 1,4 and 3,4 units was apparent. The methine-proton (H3) in a 3,4 unit showed a broad peak centered around 1.5 ppm in C6D6. The overlapping of this signal with the methyl-proton signals at 1.73 and 1.63 ppm resulted in some uncertainty in the determination of the microstructure of polyisoprene which contained a considerable amount of 3,4 unit.

Methylene and phenyl C1 carbon signals of polystyrene are assigned on the basis of the signal assignments of styrene oligomers. Polystyrenes prepared with benzoyl peroxide, n-butyllithium, and trifluoroboron etherate catalysts have random distributions with probabilities of racemic dyads of 0.54, 0.56, and 0.45, respectively.

Copolymerisation effectuee dans le toluene. Chromatographie sur gel des produits d'ozonolyse par rapport a la relation temps-conversion et temps-composition du copolymere

Gas-phase 1 H NMR spectra of 1,2-dichloropropane (1,2-DCP) and 1,2-di(methoxy- d 3 )-propane (1,2-DMP) have been measured. The conformational energies of these molecules in the gas phase were determined from the observed coupling constants under a three rotational isomeric state model and are compared with the theoretical values from MM2 molecular mechanics and MNDO molecular orbital calculations. The results indicate that gas-phase NMR is useful method for the determination of conformational energies of relatively complex molecules, and that the MNDO results are more reasonable than the MM2 results for molecules containing electronegative atoms such as oxygen.