The influence of terminal group and repeat unit structure on mass-mobility correlations observed for homologous series

Mass-mobility correlations were investigated by ion mobility-mass spectrometry (IM-MS) for 11 structurally-unique homologous series composed of commercially-available compounds. Structural variation involved the inclusion of different repeat units (i.e., glucose, propylene glycol, or ethylene glycol) in oligomeric series and different terminal groups in CH₂-homologous series. Terminal group structures included both aliphatic and aromatic acids, as well as aliphatic and aromatic amines. Mass-mobility correlations were also investigated for select CH₂-homologous series identified in a pyrolysis bio-oil and compared with results observed for commercial series. A linear mass-mobility correlation (R ² ≥ 0.996) was established for all series except those in which a substantial change in the gas-phase conformation of ions was probable. Slopes observed for CH₂-homologous series with a single terminal group were significantly steeper than slopes observed for series containing two terminal groups. Additionally, a correlation between slope and double bond equivalents (DBE) suggested that the CH₂-homologous series identified in bio-oil were structurally similar to commercial series containing two terminal groups.     

Synthesis and characterization of chiral azo LCPs with optical properties

ABSTRACT

In this study, we designed, synthesised and characterised two series of cholesteric liquid crystal polymers, QP series and ZP series. With polymethylhydrosiloxane as the main chain, QP series were synthesised by copolymerisation between the monomer M₁ containing a cholesteryl mesogenic unit and the monomer M₂ with a hydroxyl. ZP series, meanwhile, were synthesised by esterification between QP series members and the monomer M₃, a carboxylic acid with an azo mesogenic unit. We characterised chemical structures of all the monomers and polymers by FT-IR and ¹H-NMR, which proved that the target monomers and polymers had been obtained. We observed dramatic colour changes after the introduction of monomer M₃ and Grandjean textures from both QP series and ZP series using POM. In addition, strong selective reflection could be observed as well. Then, we characterised the thermal properties of polymers by DSC, TGA and XRD to explore their phase transition behaviours further. Their photoresponsive and photochromic properties were characterised by UV-Vis spectrum.     

Heterocyclic benzothiazole-based liquid crystals: synthesis and mesomorphic properties

Two homologous series of 2-(4-alkanoyloxybenzylidenamino)benzothiazoles and 2-(2-hydroxy-4-alkanoyloxybenzylidenamino)benzothiazoles were synthesised and characterised. Their molecular structures differed wherein the latter comprised a lateral hydroxyl group, unlike the former. Spectroscopic techniques such as FT-IR, ¹H & ¹³C NMR and mass spectrometry together with elemental analysis were employed to elucidate the molecular structures. The transition temperatures and their mesophases were determined by differential scanning calorimetry, optical polarising microscopy and X-ray diffraction techniques. Members with decanoyloxy till hexadecanoloxy chain in the series without the lateral hydroxyl group each exhibited a smectic A phase, while those in the series with the lateral hydroxyl group were non-mesogenic. The mesomorphic properties of the present series were compared with other structurally related series to establish the chemical structure–mesomorphic properties relationship.     

原子荧光法测定汞标准系列溶液稳定性的探讨

利用原子荧光光谱法测定水中汞含量的方法,对三组不同方法配制的汞标准系列溶液,分别进行两次时隔一个月的试验,绘制标准曲线,并分别在标准曲线上做同一汞标准样品的准确度实验。实验结果表明,不同方法配制的标准系列溶液在一个月后稳定性有所不同,其中不加固定液和稀释液的标准系列溶液反而具有更好地稳定性和准确性。     

Application of Maclaurin Series in Relating Interatomic Potential Functions: A Review

This paper provides a short review on the application of Maclaurin series in relating potential functions within the same category of interatomic interaction. The potential functions covered are those commonly adopted in computational chemistry softwares. While various mathematical approaches have been employed in generating relationships amongst potential functions, the use of Maclaurin series has been prevalent recently due to the increasing application of polynomial series-type potential functions. In the case of covalent bond-stretching, the Maclaurin series for the exponential function is used to transform the Morse potential into the polynomial series potential, and vice versa. For covalent bond-bending, Maclaurin series for the sine and cosine functions were employed to extract polynomial angle series potential from the Fourier series and harmonic cosine potential functions, and vice versa. Finally, both the exponential and the 1/(1 – x) expressions in Maclaurin series were used in obtaining the exact relationship for the repulsive terms between two potential functions.     

New chiral Schiff's bases with a 1,3,4‐thiadiazole ring in the mesogenic core: synthesis,mesomorphic and ferroelectric properties

Two new homologous series of chiral esters derived from Schiff's bases containing a 1,3,4‐thiadiazole unit (series 6 and 7) were synthesized and their liquid crystalline and ferroelectric properties investigated. All the compounds of series 6 exhibit SmC*–SmA dimorphism and the compounds of series 7 exhibit a SmC* phase. All the compounds of these series are ferroelectric liquid crystals.     

Phase and optical behaviours of chiral-azo liquid crystal polymethylsiloxanes with isosorbide units

ABSTRACT

In this study, we synthesised two series of cholesteric liquid crystal polymers CPQ and CPZ series. First, we prepared four different monomers ML₁ containing a cholesteryl group, ML₂ containing a cyano group, ML₃ containing a phenolic hydroxyl group and ML₄ containing isosorbide with azo groups. With the polymethylsiloxanes as the main chain, CPQ series were then synthesised by copolymerisation among the monomers ML₁, ML₂ and ML₃ and CPZ series were synthesised by esterification between the CPQ series and the monomer ML₄. ¹HNMR and FT-IR spectra confirmed the chemical structures of all the monomers and polymers. The mesomorphic behaviours and thermal properties were investigated by TGA, DSC, POM and XRD. Both the CPQ and CPZ series exhibited excellent thermal stability and reversible phase transitions, as well as interesting Grandjean textures under POM. CPZ series showed higher optical activity than CPQ series due to the introduction of the isosorbide group and the azo group, which could tune the pitch to make Bragg selective reflection appear more easily. UV–Vis spectra investigated the photoresponse behaviours of CPZ series thoroughly.     

Benzimidazole- and oxadiazole-modified aromatic polyimides

Three series of aromatic primary diamines were synthesized. The first series of three contained one or two hydrazide groups. The second series of five contained one or two oxadiazole groups. The third series of four contained one or two benzimidazole groups. Reaction of each diamine with either pyromellitic dianhydride or 3,4,3′,4′-benzophenonetetracarboxylic dianhydride gave a series of soluble polymeric amic acids, from which films of good thermal stability were cast. The heat-cured films were either oxadiazoleimide or benzimidazole-imide polymers, depending upon the diamine used. When hydrazide-amic acid polymers were heated, the conversion of amic acid to imide was essentially complete before any substantial portion of the hydriazide linkages were converted to oxadiazole. The latter conversion was accompanied by degradation. A better method of preparation for these polymers is through the oxadiazole contaning diamines. One hydrazide-imide polymer was prepared from trimellitic anhydride and was converted to an oxadiazole-imide by heating. The reaction of equimolar quantities of a dianhydride with 3,5,2′-triaminobenzanilde gave a soluble polymer which was converted to a benzimidazole-imide by heating.     

DISTINGUISHING OF TWO VOLCANIC ROCK SERIES IN THE LANCANG GROUP, YUNNAN PROVINCE, SW CHINA AND ITS GEOLOGICAL IMPLICATION

The detailed study on petrochemistry and geochemistry shows that meta-volcanics from Huimin and meta-basalts from Suyi belong, respectively, to different volcanic series. The former is of non-alkalic volcanic series and the latter is of straddle A-type alkslic series. Based on their geochemical characteristics of REE, LIL, HFS and Nd, Sr isotope elements, we suggest that Huimin volcanics were formed in an island arc setting and Suyi basalts were formed in a back-continental arc extensive setting. These two volcanic series have not petrogenic relationship.     

Contrasting thermal behavior and low-temperature flexibility of PDMS-grafted and poly(2-ethylhexyl acrylate)-grafted polyurethane

Polydimethylsiloxane (PDMS) was grafted onto polyurethane (PU) to form a P series, and 2-ethylhexyl acrylate (EHA) was graft-polymerized onto PU to form an E series. The spectroscopic, thermal, tensile, shape memory, and low-temperature flexibility properties of the P and E series were compared. With an increase in the PDMS content, the T_g of the P series gradually increased, whereas the T_g of the E series was not affected by an increase in the EHA content. The tensile strength of the P and E series sharply increased with the PDMS or EHA content without a significant decrease in tensile strain. The shape recovery of the P and E series remained high after four repeated tests. However, shape retention of the P series significantly decreased with an increase in the PDMS content. Finally, the P series demonstrated excellent low-temperature flexibility from ?35°C compared with the E series and control PUs.     

Thermo-XRD-analysis of montmorillonite treated with 1,4-diaminoanthraquinone

Charcoals formed during the thermo-XRD-analysis of montmorillonite (MONT) complexes with the dye 1,4-diaminoanthraquinone (DAAQ) were investigated by using curve-fitting calculations. Five saturated dye solutions were prepared (i) in distilled water and (ii–v) in 0.1, 0.5, 1.0, and 2.0 molar HCl. Two series of dye-clay complexes were prepared by using clay suspensions of 0.6 %and of 0.006 % labeled first and second series, respectively. Five dye-clay complexes were prepared of each series by adding 25 mL of dye solution to 25 mL of clay suspension. There is no free dye in complexes of the first series, but those of the second series, which were synthesized with a high ratio between dye and clay, contain non-adsorbed dye even after five washings. Complexes of the first series are loaded with very small amounts of molecular and protonated DAAQ (5–24 mmol DAAQ per 100 g clay), and their spacings are 1.25–1.54 nm suggesting the presence of tactoids with protonated or molecular DAAQ lying parallel to the clay layers. No carbon analyses were performed to the second series complexes. In addition to tactoids with spacing of 1.32 nm, they contain tactoids with spacings of 1.81–1.96 nm, suggesting that intercalated DAAQ are lying perpendicular to the clay layers. Three types of intercalated charcoal are identified in both series during the thermal analysis, one type with a low thermal stability and two types with high thermal stabilities. Charcoals of the second series complexes preserve the geometry of the original complexes up to high temperatures.     

两个系列星型准八极矩分子单光子和双光子吸收性质的理论研究

采用DFT/B3LYP/6-31G*和ZINDO-SOS方法, 系统地研究了两个系列(以苯为中心的a系列和以三苯胺为中心的b系列)星型准八极矩分子及其单枝物的单光子和双光子吸收性质. 结果表明, b系列分子有较大的双光子吸收截面和更长的单光子和双光子吸收波长. 星型三分枝分子的双光子吸收截面较其单个分枝增长了超过3倍因为存在分枝间的相互作用. 含1,3,4-噁二唑的分子比含2,1,3-苯并噻二唑的分子有更大的双光子吸收截面但是最大吸收波长却蓝移, 不在红外或近红外区域.     

Distinction of gaseous soot precursor molecules and soot precursor particles through photoionization mass spectrometry

Samples were drawn from sooting premixed low-pressure ethylene oxygen flames and investigated through photoionization mass spectrometry using either KrF or ArF lasers as the radiation source. With the former, mass spectra were obtained as described in the literature and characterized through a series of signal groups, one for each C-number and extending to about m/z 1000, assigned as a PAH series. When the ArF laser was used the same series was observed with a somewhat higher sensitivity. In addition, a new series was observed overlaid on the PAH series and starting at about m/z 680. The new series exhibited abundant ions and it completely dominated the spectrum beyond m/z 1000. This series was identified as being the spectrum of soot precursor particles. Through measurement of the ionization order it was concluded that at least two photons are needed for ionization of PAHs whereas the particles need only one photon. Consequently, they can be measured with high sensitivity when an ArF laser is used as the radiation source. Furthermore, the discrimination of soot precursor molecules and soot precursor particles becomes possible through photoionization and this enables an improved understanding of the mass spectra. This should allow a particle growth mechanism to be deduced in the near future.     

Azomesogens with polar chloro,nitro and phenolic –OH substituents

Two new mesogenic homologous series containing chloro, nitro and phenolic hydroxy groups were synthesised and their molecular structures characterised by a combination of element analysis and standard spectroscopic methods. The mesomorphic behaviour of the compounds of both series was investigated by polarising optical microscopy and, in some cases, differential scanning calorimetry. All the compounds of both the series exhibit an enantiotropic nematic mesophase. In series I higher members also exhibit an enantiotropic smectic A (SmA) mesophase, whereas in series II the enantiotropic SmA mesophase commences somewhat earlier for the middle members. The mesomorphic properties of both series are compared with each other and also with the properties of other structurally related series to evaluate the effects of different polar substituents on mesomorphism.     

New 1,2,4- and 1,3,4-oxadiazole materials: synthesis, and mesomorphic and luminescence properties

The synthesis and liquid crystalline properties of new series of 1,2,4- and 1,3,4-oxadiazole derivatives (2a-f and 5a-f respectively) are reported. These compounds contain only one terminal flexible alkoxy chain, the other terminal substituent is a protecting benzyl group. All compounds of series 2 exhibit an enantiotropic nematic phase. The homologue with the longest chain (2f) displays an enantiotropic dimorphism smectic A- nematic. None of the compounds of series 5 shows mesomorphism and only crystal-isotropic transitions were observed. The liquid crystalline properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray measurements. Luminescence properties, in chloroform solution, of 2f and the series 5 compounds were evaluated. Good photoluminescence quantum yields for compounds of series 5 were observed. Compound 2f, incorporating the 1,2,4-oxadiazole ring shows a very strong reduction in emissive properties.     

Synthesis of two naphthyl-containing homologous series of mesogenic ligands and the related metallomesogens containing Cu(II)

Two new naphthyl-containing homologous series of mesogenic ligands, the 4-n-alkoxy-2-hydroxybenzylidene-2'-naphthylamines (series I) and 4(4'-n-alkoxybenzoyloxy)-2-hydroxybenzylidene-2'-naphthylamines (series II), as well as the related metallomesogens of higher homologues containing a Cu(II) atom, have been synthesized. All the ligands and complexes were characterized by a combination of elemental analysis and standard spectroscopic methods. In series I, n-heptyloxy and n-octyloxy derivatives are non-mesogenic whereas the remaining higher members synthesized exhibit a monotropic nematic mesophase. In series II, all the members synthesized exhibit an enantiotropic nematic mesophase. All the metallomesogens of series I synthesized exhibit a monotropic smectic A mesophase, except for the n-octyloxy derivative, which is non-mesogenic, whereas metallomesogens of series II exhibit enantiotropic nematic mesophases up to the n-tetradecyloxy derivatives; the n-tetradecyloxy and n-hexadecyloxy derivatives also exhibit smectic C mesophases. All the members of series II and their metallomesogens exhibit mesophases with wide temperature ranges and greater thermal stability as compared to series I and their metallomesogens, respectively. The mesomorphic properties of both the present series and their metallomesogens are compared with each other and with other structurally related series to evaluate the effect of the naphthalene moiety on mesomorphism.     

Imidazole-based potential Bi- and tridentate nitrogen ligands: synthesis, characterization and application in asymmetric catalysis

Twelve new imidazole-based potential bi- and tridentate ligands were synthesized and characterized. Whereas in the first series the alpha-amino acid and imidazole moieties were linked by an amino bond, in the second series the tridentate ligands, containing two imidazole groups, were separated by an amide bond. The first series was obtained by the reductive amination of 2-phenylimidazole-4-carboxaldehyde with alpha-amino acid esters. The tridentate ligands were prepared from 2-phenylimidazole-4-carboxylic acid and chiral amines. In the Henry reaction, the amines were revealed as a more reactive species than the less nucleophilic amides, however the enantiomeric excesses were generally poor.     

Optical Properties of New Third-Order Nonlinear Materials Modified by Click Chemistry

A high-yielding click reaction was used to synthesize a series of highly conjugated, symmetrical, as well as asymmetrical compounds with a benzene core. Cyclic voltammetry and ultraviolet/visible absorption spectroscopy were carried out, and proved that the side groups of the benzene derivatives played an important role in the energy gaps, and affected the third-order non-linear optical response. The maximum absorption wavelength of the series of benzene derivatives showed an obvious red-shift. Moreover, the addition of resilient electron-withdrawing groups significantly narrowed the energy levels as compared with precursors. The third-order nonlinear properties of this benzene derivative were tested by the Z-scan technique. The expected properties of this series of molecules were obtained, and it was found that the series of molecules undergoes a transition from reverse saturable absorption to saturable absorption, which has certain reference significance for a nonlinear optical field.     

13C- and 1H-NMR. Assignments for colchicine derivatives

The ¹³C-NMR. spectra of a number of colchicine derivatives are given comprising examples of the normal series ( 4→10 ), iso series ( 11→16 ) and colchicine series ( 17 ), which were either reported in the literature or obtained by partial synthesis or degradation reactions. The ¹³C-NMR. assignments were made by comparisons with known compounds and selective single-frequency offresonance decoupling experiments. Selective proton decoupling experiments have also allowed assignments of the H —C(11) and H —C(12) protons of the iso and colchicine series.     

Symmetric esters derived from 1,3,4-oxadiazole: synthesis,mesomorphic properties and structural study by semi-empirical calculations

Three homologous series of symmetric esters derived from 2-alkylthio-5-(p -hydroxy)phenyl-1,3,4-oxadiazole (series 3, 4 and 5) were synthesized and their liquid crystalline properties investigated by optical microscopy and differential scanning calorimetry. Depending on the chain length, nematic and smectic C phases were observed in the series 3 ; smectic A and smectic C phases in series 4. None of the homologues of series 5 shows mesomorphic properties. These three series are compared with other previously reported oxadiazoles. A structural study of AM1 semi-empirical calculations is also described.