Calculation of the Band Intensities of the IR Spectra of Oriented Polymers

An attempt has been made to extend the theory of IR spectra of polymers to oriented polymers. Formulas for the absorption-band intensities in polarization IR spectra of oriented polymers reflecting the dependence of the polarized absorption-band intensity on the structural and orientation characteristics of polymers have been obtained. These formulas permit calculating the intensity of polarized absorption bands at different degrees of orientation of the polymer.     

Turn-on circularly polarized luminescent (CPL) molecular system realized by thermo-driven Newman–Kwart rearrangement reaction from CPL-silent O- to CPL-active S-thiocarbamate groups at peripheral position of 1,1′-binapthyl rings

Although chiral 1,1′-binaphthalene-2,2′-diyl-O,O-bis(N,N-dimethylthiocarbamate) (1) revealed no circularly polarized luminescence (CPL) signals, Newman–Kwart rearrangement of O-thiocarbamate groups at 1 yielded clear CPL signals from 1,1′-binaphthalene-2,2′-diyl-S,S-bis(N,N-dimethylthiocarbamate) (2), which acts as a CPL-gen molecule.     

Dual Upconverted and Downconverted Circularly Polarized Luminescence in Donor–Acceptor Assemblies

Through mimicking both the chiral and energy transfer in an artificial self‐assembled system, not only was chiral transfer realized but also a dual upconverted and downconverted energy transfer system was created that emit circularly polarized luminescence. The individual chiral π‐gelator can self‐assemble into a nanofiber exhibiting supramolecular chirality and circularly polarized luminescence (CPL). In the presence of an achiral sensitizer Pd^II octaethylporphyrin derivative, both chirality transfer from chiral gelator to achiral sensitizer and triplet‐triplet energy transfer from excited sensitizer to chiral gelator could be realized. Upconverted CPL could be observed through a triplet–triplet annihilation photon upconversion (TTA‐UC), while downconverted CPL could be obtained from chirality‐transfer‐induced emission of the achiral sensitizer. The interplay between chiral energy acceptor and achiral sensitizer promoted the communication of chiral and excited energy information.     

High-order Harmonic Generation of Aligned Acetylene in Elliptically Polarized Strong Laser Fields?

We perform an experimental study on high-order harmonic generation (HHG) of aligned acetylene molecules induced by a 35-fs 800-nm strong laser field, by using a home-built HHG spectrometer. It is observed that the molecular HHG probability declines with increasing the laser ellipticity, which is in consistence with the deduction from the well-known tunneling-plus-rescattering scenario. By introducing a weak femtosecond laser pulse to nonadiabatically align the molecules, we investigated the molecular orbital effect on the HHG in both linearly and elliptically polarized driving laser fields. The results show that the harmonic intensity is maximum for the molecular axis aligned perpendicularly to the laser electric field. It indicates that both the highest occupied molecular orbitals (HOMO) and HOMO-1 contribute to the strong-field HHG of acetylene molecules. Our study should pave the way for understanding the interaction of molecules with ultrafast strong laser fields.     

Realizing representations on generalized flag manifolds

Let G be a complex reductive linear algebraic group and a real form. Suppose P is a parabolic subgroup of G and assume that P has a Levi factor L such that is a real form of L.Using the minimal globalization V _min of a finite length admissible representation for L ₀, one can define a homogeneous analytic vector bundle on the G ₀ orbit S of P in the generalized flag manifold . Let denote the corresponding sheaf of polarized sections. In this article we analyze the G ₀ representations obtained on the compactly supported sheaf cohomology groups .     

Photochemistry with Circularly Polarized Light

The reactions induced by circularly polarized light are reviewed and a general discussion of the induction of optical activity by circularly polarized light is presented. It is concluded that three different mechanisms, or their combinations, can cause asymmetric induction. In each case the optical yield is dependent on the optical anisotropy factor g, the ratio between the circular dichroism (Δ?) and the extinction coefficient (?). The results are discussed in terms of the presumed mechanisms, and particular attention is paid to the asymmetric synthesis of helicenes. It is concluded that this kind of photochemistry may have analytical importance.     

Reduced-size polarized basis sets for calculations of molecular electric properties. II. Simulation of the Raman spectra

The accuracies of the calculated vibrational frequencies and Raman intensities given by two new, highly compact Pol-type basis sets, Z2PolX and Z3PolX, have been determined and compared to the 6-31G(d), PolX, and aug-cc-pVTZ basis sets. Calculation of accurate Raman intensities has previously required large basis sets, but the ZmPolX basis sets are smaller even than PolX, which are the most compact basis sets able to calculate accurate Raman intensities. For the largest compound studied, C5H10O2, Z3PolX required more than an order of magnitude less CPU time than PolX, which has been shown to be 10 times faster than aug-cc-pVTZ. Two sets of test molecules were studied: one was a series of small molecules for which experimental values for absolute Raman activities were available; the second was a series of medium-sized molecules (mainly common organic solvents) where only relative Raman band intensities were available. The accuracies of the Raman intensities given by both of the ZmPolX basis sets were good compared to those of the PolX and aug-cc-pVTZ sets, and much better than the 6-31G(d) values. The errors in even unscaled frequency values <2000 cm(-1) were also acceptable and were slightly lower for Z3PolX than Z2PolX (30 cm(-1) vs. 48 cm(-1)). The combination of good intensity and frequency data meant that for the medium-sized organic molecules there was a close correspondence between the simulated Raman spectra and experimental data, and that the observed bands could easily be assigned on the basis of these calculations. Achieving this level of accuracy in the simulations at modest computational cost should now allow computational methods to be combined with experimental Raman studies much more widely than is currently the case.     

Effect of titanium dioxide nanoparticles on polymer network formation

This work presents a study of the effect of nanoparticles on polymer composites to develop a powerful polymer dispersed liquid crystal materials. Tri propylene glycol diarcrylate/titanium dioxide nanocomposites were produced at various titanium dioxide fractions ranging between 0 and 1?wt%, through ultraviolet curing technique during 30?min. Different technics such as polarized optical microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis were used to characterize the samples. A dynamic swelling of polymer network was also investigated. The evolution of the acrylic double-bond conversion shows a decrease in the absorption intensity at 1637?cm^?1. It is noted that the conversion rate decreases from 0.1 to 1?wt% of titanium dioxide nanoparticles. An increase in glass transition temperature is observed by differential scanning calorimetry. The thermogravimetric analysis results reveal a highly improved thermal stability upon the addition of the reinforcing phase. The follow of kinetics swelling of polymer network shows a decrease of the swell ratio with the inclusion of titanium dioxide nanoparticles.     

聚乙烯醇中的紫外偏振线性聚炔分子

本文通过研究共轭线性碳链分子，聚炔H(C≡C)_nH (n=5∽7)的电子吸收带，设计了适用于UV的光偏振膜. 激光烧蚀的聚炔分子被分散在聚乙烯醇膜中. 结构各向异性的性质使得多炔分子的UV吸收跃迁偶极子与分子轴平行，并且吸收仅发生在沿着分子轴具有电子矢量幅度的电磁波上. 多炔分子在固体聚乙烯醇膜中作为特定波长入射光的偏振分量之一的选择性吸收剂. 使用可旋转的偏振UV光研究包含聚炔分子的拉伸聚乙烯醇膜的吸收强度的角度依赖性，并根据线性二向色性理论中有序参数进行分析.