Soluble functional polyacetylenes for optical limiting: Relationship between optical limiting properties and molecular structure

Four polyacetylenes containing chromophores with different conjugation bridge structure or terminal substituents were designed and prepared by using [Rh(nbd)Cl]₂ as catalysts, respectively. Their structures and properties were characterized and evaluated by IR, NMR, UV, TGA, optical limiting and nonlinear optical analyses. All the polymers show high thermal and photo stability and novel optical limiting properties. The functional polyacetylene with stilbene pendant shows better optical limiting property than that with azobenzene chromophore pendant. Their optical limiting mechanisms are mainly originated from reverse saturable absorption of molecules. Their nonlinear optical properties are significantly affected by their molecular structures and the shorter spacer group will be beneficial in increasing the electronic interaction between chromophore pendant and polyacetylene conjugation backbone to result in higher third-order optical nonlinearity.     

An observed correlation between flow and electrical properties of pharmaceutical blends

We study the relation between flow and electrical conductivity of multiple formulations of pharmaceutical powder blends. Ten formulations were tested, consisting of two excipient sets, two active preparations, and a variety of food-grade additives including magnesium stearate (MgSt), and ionic and conductive materials such as ascorbic acid, talc, sodium carbonate, colloidal silica and TiO₂. Electrical impedance, flow index and dilation were independently measured for all of the blends, and a strong correlation was found between every pair of these three properties. The relation between flow and dilation has been observed before; we find for the first time that there is an exponential relationship between flow index or dilation and impedance. This indicates that cohesive powder behavior depends on powder electrical properties, raising the questions of whether additives such as MgSt affect friction and conductivity per se and what mechanism and phenomenon links cohesion and conductivity.     

Synthesis and properties of optically active substituted polyacetylenes having carboxyl and/or amino groups

Polyacetylenes having carboxyl and/or amino groups in the side chain were synthesized by the polymerization of N-(2-propynyloxycarbonyl)-l-alanine (1) and l-alanine N-propargylamide (2) catalyzed with a rhodium cation complex. Poly(1_0.5-co-2_0.5) exhibited a larger CD signal than the homopolymers. The polymer mixtures obtained by the polymerization of 1 in the presence of poly(2), and those obtained by the polymerization of 2 in the presence of poly(1) showed specific rotations larger than calculated. The polymerization of propargylamine in the presence of poly(1) did not exhibit significant effect, while the polymer mixtures obtained by the polymerization of propiolic acid in the presence of poly(2) exhibited [α]_D of positive sign, although poly(2) alone exhibited [α]_D of negative sign.     

双子表面活性剂的结构与性质间关系的研究

采用量子化学和分子力学方法优化了双子表面活性剂阳离子的几何模型，得到了轨道能级、生成焓和弯曲能等数据，计算表明结果，随着联结基因长度（s）增大，最高占据分子轨道能级（EHOMO）和最低空轨道能级（ELUMO）依次升高，且两者能级差（△E）也依次增大，用量子化学方法计算的与按键焓加和规则计算的这些阳离子的生成焓之差随联结基团长度增大而迅速增大。分析发现，这些现象与极性头两个氮原子之间C-C键的平均键长（R^-C-C）有关，经拟合，相关系数为0.945。同时还讨论了弯曲能与形成胶束的标准自由能变化（△Gmin）之间的关系。     

Relation between physical structure and electrical properties of diamond-like carbon thin films

Diamond-like carbon (DLC) belongs to very interesting materials used for a number of practical applications. Its properties strongly depend on the method of deposition and on the deposition parameters. In particular, the electrical properties of DLC films obtained by RF PCVD discharge depend substantially on the preparation conditions. Influence of deposition conditions on the physical structure and chemical content is discussed. Both the drift mobility of charge carriers and the electrical conductivity of DLC films strongly depend on deposition conditions. The electrical conductivity results are explained in terms of hopping mechanism. At the temperatures below 260 K, the hopping among states in a narrow band of states dominates; at the higher temperatures, the band-to-band transitions are suggested to occur. A model of the forbidden gap explaining the observed electrical properties of DLC films is proposed. Experimental results concerning the electrical conduction of DLC/Si heterostructures are also presented and discussed. The difference in the properties of DLC/n-Si and DLC/p-Si structures may suggest that the electron transport via localised states dominate in the investigated DLC films. Recombination lifetime of charge carriers in DLC films is measured using both dielectric spectroscopy and detection of decay of photocurrents. The lifetime is found to be of the order of 0.3–0.4 ms, which is quite long in comparison with classical doped silicon semiconductors.     

Synthesis and properties of helical polyacetylenes containing carbazole

Novel acetylene monomers containing carbazole with chiral menthyl and bornyl groups, 9-(1R,2S,5R)-menthyloxycarbonyl-2-ethynylcarbazole (1), 9-(1S,2R,5S)-menthyloxycarbonyl-2-ethynylcarbazole (2), 9-(1R,2S,5R)-menthyloxycarbonyl-3-ethynylcarbazole (3) and 9-(1S)-bornyloxycarbonyl-2-ethynylcarbazole (4) were synthesized and polymerized with a Rh catalyst to give the corresponding polymers [poly(1)-poly(4)] with moderate M_n value of (11.5-92.2) × 10³ in good yields (77-89%). CD spectroscopic studies revealed that poly(1), poly(2) and poly(4) took predominantly one-handed helical structure in CHCl₃, THF, toluene, and CH₂Cl₂, while poly(3) did not. Addition of methanol to CHCl₃ solutions of poly(1) and poly(2) resulted in the formation of aggregates showing smaller CD signals at 275 and 320 nm. The helical structure of poly(1) and poly(2) was very stable against heating. The polymers emitted fluorescence in 0.40-2.90% quantum yields. Poly(4) exhibited an obvious oxidation peak at 1.10 V. The polymers were thermally stable below 300 °C.     

Revealing the correlation between molecular structure and dielectric properties of carbonyl-containing polyimide dielectrics

Polymer dielectrics with outstanding heat resistance and advanced dielectric properties are of great importance for high-temperature capacitors in the applications of hostile circumstances. In this work, a series of aromatic carbonyl-containing polyimides (CPI) are prepared from the carbonyl dianhydride and different diamines. The correlation between molecular structure (i.e., different linked structure (─O─, ─CH2─, ─SO2─) in diamines, the length of repeating unit and the linked position (para-para or meta-meta), and properties is revealed in detail to obtain CPI dielectrics with excellent thermal resistance (glass transition temperature, T_g: 241~352°C), reasonably high dielectric constant (3.99~5.23), low dissipation factor (0.00307~0.00395), and admirable breakdown strength (425~552 MV/m) simultaneously. Particularly, CPI-5 with carbonyl structure in dianhydride and sulfonyl group in diamine proves to exhibit discharged energy density and charge–discharge efficiency of 6.34 J/cm³ and 92.3% at 500 MV/m, respectively. In addition, CPI-5 also displays stable dielectric properties in temperature range of −50‑200°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47883.     

Structural analysis and electrical properties of halogen substituted poly(paraphenylene)

Poly(tetrafluoro-p-phenylene) was prepared by the modified Ullmann reaction. The average degree of polymerization was determined from electron impact mass spectrometry and was found to be n = 8. The structure of the polymer was studied using infrared, Raman, ultraviolet absorption spectroscopy and differential scanning calorimetry. Polymerization of 1,4-diiodo-2,3,5,6-tetrafluorobenzene resulted in the disappearance of the characteristic C-I vibrations and the appearance of new absorption bands in the infrared and Raman spectra. At room temperature poly(tetrafluorophenylene) is an insulator. Attempts to increase the dc conductivity on FeCl₃ and sodium doping were unsuccessful until now.     

Structural,electrical, and magnetic properties of Zn substituted magnesium ferrite

Zinc substituted magnesium (Mg–Zn) ferrites with the general formula Mg_1−xZn_xFe₂O₄ (x=0.00, 0.25, 0.50, 0.75, and 1.00) were prepared using the solution combustion route. The dried powder after calcination (700 °C for 2 h) was compacted and sintered at 1050 °C for 3 h. The structural, morphological, dielectric and magnetic properties of the sintered ferrites were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), impedance spectroscopy, and vibration sample magnetometry (VSM). The XRD analysis of sintered samples confirmed that the expected spinel cubic phase was formed for all samples. The crystallite sizes evaluated using Scherre's formula were found to be in the range of 47–80 nm. SEM analysis showed homogeneous grains with a polyhedral structure. The electrical conductivity increased with increasing frequency, which is normal dielectric behavior for such materials. The dielectric constant, dielectric loss tangent, and AC conductivity were found to be lowest for x=0.50. The VSM results showed that the zinc concentration had a significant influence on the saturation magnetization and coercivity.     

Synthesis and properties of polyacetylenes containing carbazolylmethyl groups

Novel acetylene monomers containing carbazolymethyl groups, 3,5-bis[(3,6-di-t-butyl)carbazolylmethyl]-1-ethynylbenzene (1), 3-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (2), and 4-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (3) were synthesized, and polymerized with [(nbd)RhCl]₂-Et₃N, Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃], and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 1600 to 115,000 were obtained in 18%-quantitative yields. The UV-vis absorption band edge wavelengths of the polymers obtained with W catalyst were longer than those of the Rh-based polymers. The photoluminescence quantum yields of the W-based polymers were 1.1-3.1%, while those of the Rh-based ones were 0.18-4.1%.     

Temperature-dependent electrical properties of B-site zinc substituted bismuth sodium titanate piezoceramics

Lead-free ceramics of B-site Zn substituted Bi_0.5Na_0.5TiO₃, with the formula of (1 ? x)Bi_0.5Na_0.5TiO₃–xBi(Zn_0.5Ti_0.5)O₃ (BNT–BZT, x = 0.01, 0.04, 0.07) have been prepared. These compositions have rhombohedral, rhombohedral–tetragonal morphotropic phase boundary, and tetragonal crystal structure, respectively. The polarization–electric field (P–E), bipolar and unipolar strain–electric field (S–E) curves of all the compositions are measured as the functions of temperature. The temperature-dependent values of the remnant polarization, maximum polarization, coercive field, bipolar and unipolar strain, as well as the shape change of P–E and S–E curves have been comparatively investigated and discussed. The observed different temperature-dependences of the above parameters are attributed to the fact that the introduction of BZN reduces the depolarization temperature and enhances relaxor characteristics, which is consistent with the temperature-dependent dielectric properties. These results are valuable in understanding and further designing noval BNT-based lead-free piezoelectric systems with high recoverable strain.     

Influence of calcium substitution on structural and electrical properties of substituted barium titanate

Ba_0.80−xCa_xPb_0.20Ti_0.90Zr_0.10O₃ ceramics (x = 0, 0.10 and 0.20) were synthesized by solid state reaction. Samples microstructure and dielectric, ferroelectric and piezoelectric properties were studied. Dielectric constant (?), coercive field (E_c), remanent polarization (P_r) and ratio of remanent to spontaneous polarization (P_r/P_s) were studied at different temperatures. Sample with x = 0.10 was found to have maximum and comparatively more stable P_r/P_s ratio over a wide temperature range. Dielectric loss was found to improve with increase in x whereas piezoelectric charge coefficient d₃₃ was found to decrease with increase in x.     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Strong corelation between magnetic and electrical subsystems in diamagnetically substituted hexaferrites ceramics

The BaFe_11.9Al_0.1O₁₉ M-type hexagonal barium ferrite was obtained by a standard ceramic method (powder synthesis in a solid state reaction method). at 4.2, 50, 100, 200, 300, 400, 630 and 730 K via neutron powder diffraction (NPD) on a high-resolution Fourier diffractometer. An anomal microstructural transition on atomic level has been observed in BaFe_11.9Al_0.1O₁₉ due to transition from a centrosymmetric to a non-centrosymmetric Space Group (SG). The NPD data were successfully refined for both space groups (SG): a centrosymmetric SG #194 (non-polar phase) and a non-centrosymmetric SG #186 (polar phase). The Goodness-offit quality factor (χ²) demonstrated good agreement between experimental data and theoretical model for both SG #194 and for #186. Goodness-offit quality factor (χ²) was better at low temperatures (4.2–150 K) for SG #186, while at higher temperatures (630–730 K) χ² was better for SG #194. This might be because of the two different phases in BaFe_11.9Al_0.1O₁₉ and there are mutual phase transitions at the atomic level. Dual ferroic properties (coexistence of magnetization and polarization) were demonstrated at room temperature in BaFe_11.9Al_0.1O₁₉. Strong correlation between magnetic and electrical subsystems (magnetoelectrical effect – ME) has been shown. Temperatures dependences of the polarization, magnetization and ME effect were studied.     

The electrical conductivity properties and structures of substituted poly(phenylene sulphides), synthesized from phenols and sulphur

Summary We have synthesized polyphenylenesulphides, using phenols, xylenes, sulphur and halogens as starting materials. The substituted and partly branched polyphenylenesulphides obtained have been doped with iodine (I₂). The structures have been investigated by elemental analyses, IR, NMR and GPC. The electrical conductivities of these products were rather low in the region of 10^–6–10^–11 Scm^–1. Higher conductivity values were observed for the polymers containing methoxy- or acetyl-substituents compared with those containing hydroxyl groups. It is suggested that this depends, at least partly, on the absence of hydrogen bonds between the sulphur atoms and the hydroxyl groups. As was expected molecular weight also had the effect of increasing the conductivity values observed.     

Intrinsic correlation between structure,vibration spectrum and microwave dielectric properties of ferroelectric-dielectric composite ceramics

A novel series of (1-x)Ba_0.45Sr_0.55TiO₃-xMgGa₂O₄ (x = 0, 10, 30, 50, 70 wt%) ceramics was prepared by a solid-state method to investigate the relationship between their dielectric properties and ion diffusion, composition effect, and lattice vibration. XRD refinement and DFT calculations of Ba_0.45Sr_0.55TiO₃ (BST45) revealed that the substitution of Ga³⁺ and Mg²⁺, both of which have small polarizability for Ti⁴⁺, reached the saturation state at x = 10 wt%, thus decreasing the quality factor (Q value). In contrast, the addition of MgGa₂O₄ (MG) with x > 10 wt% significantly reduced the relative permittivity and improved the Q value owing to the compositional effect. The vibration spectra (Raman and FT-IR) confirmed that the Q value initially decreased owing to ion diffusion at x < 10 wt% and then increased with increasing MG content according to the composition effect. Therefore, the Q value was remarkably improved in the Ba_0.45Sr_0.55TiO₃-MgGa₂O₄ composites, with good tunability and low relative permittivity.     

Correlation between entropy state,crystal structure,magnetic and electrical properties in M-type Ba-hexaferrites

Low-entropy (un-substituted Ba-hexaferrite) and High-entropy (polysubstituted Ba-hexaferrite with Ga/In/Ti/Cr/Co ions) samples were synthesized. The crystal structure, microstructure, magnetic and electrical properties of BaFe₁₂O₁₉ and Ba(Fe_6.00Ga_1.26In_1.17Ti_1.20Cr_1.22Co_1.15)O₁₉ ceramic samples were investigated. It was established that there is a correlation between entropy state and the features of crystal structure. Magnetic properties are critically depended on entropy state and intensity of super exchange interactions. Magnetic phase separation was observed (coexistence of the classical multi domain states and magnetic “nano regions”) in HE-samples. In hexaferrites, a strong coupling between entropy state, magnetic and electrical properties was demonstrated.     

Investigation the correlation between chemical structure and swelling,thermal and flocculation properties of carboxymethylcellulose hydrogels

Hydrophilic polymer networks (hydrogels) based on sodium carboxymethylcellulose (NaCMC) and polycarboxylic acids (oxalic, succinic, citric and adipic) as cross-linking agents are synthesized by esterification reaction; one series of NaCMC hydrogels cross-linked with citric acid is prepared with acrylamide and acrylic acid (Aam/Aac) copolymers using the design of semi-interpenetrating polymer networks (semi-IPN), in order to increase their potential application for flocculation purposes. The Infrared spectroscopy (FTIR) of hydrogels confirms the esterification reaction between NaCMC and cross-linking agents. Results of swelling measurements show that citric acid in the amount of 15 wt% gives the hydrogels with the best absorption capacity. The results of Differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA) show no significant difference in thermal properties of neat and semi-interpenetrating NaCMC hydrogels. The amorphous nature of hydrogels is confirmed by X-ray diffraction analysis (XRD). The results of flocculation study show that combination of NaCMC network and Aam/Aac copolymer with initial mass ratio of 10/90 creates a theoretical platform for the production of flocculant which could show high efficacy in purifying of water dominated by positively charged particles.     

Synthesis and optical properties of polyacetylenes containing nonlinear optical chromophores

High molecular weight polyacetylenes bearing nonlinear chromophoric pendants poly[4-ethynyl-4′-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl]₂-Et₃N. The azo unit in the copolymers can be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility, all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7%. The structures and properties of the polymers were characterized and evaluated by UV, NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability (≥300 °C). They can attenuate intense laser pulses, with solutions of high concentrations showing better performances. The third-order nonlinear susceptibility of the copolymers was as high as 4.62×10⁻¹¹ esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene).     

Plasma polymerized thiophene: molecular structure and electrical properties

Polythiophene (PTh) is of interest for transistors, light emitting diodes and sensors. Plasma polymerization is a solvent-free, room temperature process that can be used to rapidly deposit thin polymer films onto a wide variety of substrates. This paper describes the synthesis of plasma polymerized thiophene (PPTh) and the dependence of molecular structure and properties on the polymerization conditions. Transparent plasma polymerized thiophene films, deposited at about 50 nm min⁻¹, had a density of about 1.75 g cc⁻¹, depending on the carrier gas used (if any) and on the plasma power. The molecular structure consisted of opened thiophene rings and included significant amounts of unsaturation, oxygen and nitrogen. When nitrogen was used as a carrier gas at a low power or when a high power was used (with no carrier gas), there was significantly more oxygen, nitrogen, and sulfur-oxygen bonds. When a high power was used, the films exhibited a higher polar component of surface tension and a higher internal stress. The undoped films exhibited non-linear current-voltage (IV) behavior typical of Schottky metal-semiconductor barriers with breakdown at reverse bias. Iodine doping yielded ohmic IV behavior, perhaps reflecting the formation of a conducting iodine percolation network.