STUDIES ON FLAVINS IN ORGANIC SOLVENTS — III. SPECTRAL BEHAVIOUR OF LUMIFLAVIN

Abstract— The absorption and fluorescence emission spectra of lumiflavin have been studied in nonaqueous solvents of different polarity. The corrected emission spectra show apparent mirror symmetry to the longest wavelength absorption maximum. In view of high molar extinction coefficient of the longest wavelength maximum in absorption spectra, constant polarization of fluorescence across it in dioxane and high values of quantum yields of Buorescence, τ→τ* character of corresponding electronic transition was proposed. Roughly linear correlation was found between transition energies and quantum yields of fluorescence on the one hand, and polarity of solvents expressed in Kosower's 'Z' values (excepting acetic acid) on the other.
In preliminary experiments it was found that lumiflavin in dioxane and in acetic acid is strongly photodecomposed by the monochromatic(436 nm) light.     

SWELLING BEHAVIOR OF ACRYLAMIDE HYDROGEL IN DIFFERENT SOLVENTS AND pHs

Swelling property of acrylamide hydrogels, prepared from aqueous solutions of acrylamide monomer having concentrations in the range of 10-60 wt% by γ-ray irradiation method using a Co-60 gamma radiation source at doses ranging 1-30.0 kGy, has been investigated under various swelling media. These swelling media were basically solvents (solutions), produced by dissolving methanol, ethanol, glucose, sucrose, sodium chloride and sodium persulfate individually with distilled water, and solutions prepared with pHs = 3, 7 and 10. The investigation was performed in order to observe the effect of these solvents and pHs as well as the influence of monomer concentrations, radiation doses and times on swelling behavior of hydrogels. Swelling values were found higher for hydrogels prepared with lower monomer concentrations (ca.20 wt%) and radiation doses (ca. 5 kGy) and showed a leveling off tendency within 24 h. The glucose solvent and the buffer solution of pH = 10 revealed significant increase of swelling of hydrogels as compared to other solutions. Results are explained based on crosslinking density in hydrogel, polymer-solvent/polymer-polymer interactions in solutions,permeability of molecules in solutions and ionization capacity of hydrogel in pH.     

超临界苯类溶剂对聚苯乙烯降解的影响

在高压间歇反应器中,温度340~370℃,以苯、甲苯、乙苯和对二甲苯为超临界溶剂研究了聚苯乙烯(PS)的降解特性.苯类物质是聚苯乙烯的优良溶剂,在超临界条件下其优异的传质、传热性能使聚苯乙烯快速降解.聚苯乙烯在不同超临界溶剂中降解转化率相近,而降解产物组成差别很大,分析了不同超临界溶剂对聚苯乙烯降解过程的影响.结果表明超临界甲苯对降解过程影响最小,苯乙烯收率最高.聚苯乙烯降解过程中,高分子链断裂和解聚同时进行,结合连续分布理论建立了聚苯乙烯降解的动力学模型,得到在超临界甲苯中聚苯乙烯链端解聚活化能为138.4 kJ.mol-1.     

VISCOMETRIC STUDY OF POLY(METHYL METHACRYLATE) AND POLYSTYRENE BLENDS IN DIFFERENT SOLVENTS

The intermolecular interaction between poly(methyl methacrylate) (PMMA) and polystyrene (PS) intetrahydrofuran (THF) and N,N'-dimethyl formamide (DMF) solvents was studied at 28℃ using a dilute solution viscometrymethod. Solvent is believed to play a key role in characterizing the viscosity behavior of the polymer solution. The intrinsicviscosity and viscosity interaction parameter were experimentally measured for the binary (solvent/polymer) and for theternary systems in two solvents. The compatibility of the polymer mixture was discussed in terms of the sign of △b_m. Theresults show that the compatibility of PMMA/PS blend in DMF is larger than that in THF.     

纤维素溶剂研究进展

概述了纤维素溶剂的重要研究进展,主要包括N-甲基吗啉-N-氧化物(NMMO)在85℃以上高温可破坏纤维素分子间氢键,导致溶解;氯化锂/二甲基乙酰胺(LiCl/DMAc)在100℃以上可溶解纤维素;1-丁基-3-甲基咪唑盐酸盐([BMIM]Cl)和1-烯丙基-3-甲基咪唑盐酸盐([AMIM]Cl)离子液体,含强氢键受体Cl-离子,通过它们与纤维素羟基作用而引起溶解.氨基甲酸酯体系则是通过尿素与纤维素在100℃以上反应转变为纤维素氨基甲酸酯,然后再溶解于NaOH水溶液中;氢氧化钠/水体系,只能溶解结晶度和聚合度较低的纤维素;NaOH/尿素、NaOH/硫脲和LiOH/尿素水溶液体系,它们预冷至-5~-12℃后可迅速溶解纤维素.主要是通过低温产生小分子和大分子间新的氢键网络结构,导致纤维素分子内和分子间氢键的破坏而溶解,同时尿素或者硫脲作为包合物客体阻止纤维素分子自聚集使纤维素溶液较稳定.低温溶解技术不仅突破了加热溶解的传统方法,而且可推进化学"绿色化"进程.共引用参考文献50篇.     

聚N-乙烯咔唑与硝基芴酮类在不同溶剂中形成的电荷转移复合物

The charge-transfer complexes of poly(N-vinylcarbazole) (Mn=7200) and nitro- fluorenones were studied with VPO in different solvents. The relationship between equilibrium constant and solvent dipole moment was examined. The results obtained from polymer and model compound were compared, and the reason of their difference was explained. The relationship between the equilibrium constant and the molecular weight was given: InK_(CT)=InK_(CT)~∞+2M_0/M(InK°-InK~∞)     

溶剂种类及组成对纤维素羧甲基化反应的影响

溶剂种类及组成对纤维素羧甲基化反应的影响张镜吾，程发，李东立，李桂风，张晓红（天津大学化学系，天津，３０００７２）关键词纤维素，混合溶剂，碱处理，羧甲基化．Ｘ－衍射校甲基纤维素（ＣＭＣ）是重要的纤维素衍生物，应用领域十分广泛．纤维素核甲基化反应主要取...     

BEHAVIOUR OF MICELLES OF A NON-IONIC SURFACTANT IN THE PRESENCE OF CONCENTRATED ELECTROLYTES AT DIFFERENT TEMPERATURES

Micelle formation of nonylphenol polypropylene polyethylene oxide (NPE-1800) was investigated in aqueous and aqueous electrolyte solutions. The study focused on the effect of temperatures, 25, 30, 35 and 40°C and on the effect of concentrated inorganic electrolytes, NaNO₃, KCI, KNO₃, K₂SO₄ and MgCl₂.6H₂O. The Critical Micelle Concentration (CMC) was determined by surface tension measurements. On the basis of the actual CMC and its temperature dependence, the thermodynamic functions of micelle formation (δH°, δS°, δG°) were calculated.

According to the experimental results, the CMC at high electrolyte concentration increases with increasing temperature. This behaviour is attributed to the salting-in mechanism.

Viscometry supports the behaviour of NPE-1800 in concentrated electrolytes and the decrease of (η is attributed to the decrease of the solvency of the electrolytic solution.     

SPECTRAL ALBEDO MEASUREMENTS IN THE UV and VISIBLE REGION OVER DIFFERENT TYPES OF SURFACES

Abstract— The spectral albedo of the earth's surface, i.e. the ratio between spectral irradiance reflected by the ground to all directions and global irradiance, was measured by a spectroradiometer in the UV and visible region from 290 nm to 800 nm with a spectral resolution of 1.5 nm at steps of 2 nm in the UV (290–400 nm) and 10 nm in the visible (400–800 nm) region. The measurements were performed over bare fertile soil, sand at the beach, concrete (autobahn) and snow as well as over different types of vegetation (grass, oats, rye, sugar-beet, stubble). As the albedo increases with increasing wavelengths for most types of surfaces considered, it is smaller in the UV than in the visible region. In the UVB region (λ < 315 nm) the measured albedo is as small as 0.016-0.017 over vegetation, 0.04-0.05 over bare fertile soil, 0.07-0.10 over concrete ("autobahn") and 0.62-0.76% over polluted snow with a small wavelength dependence. A somewhat higher albedo occurs in the UVA region (315 < λ < 400 nm) with values ranging from 0.02 over vegetation to 0.05 to 0.08 over bare soil. The albedo over dry bright sand, which is typically found at the beach, is significantly higher (0.14 at 300 nm to 0.24 at 400 nm) than over other snow-free surfaces, thus leading to an enhanced dose of biologically effective radiation at the beach.     

水杨酸及其酯类化合物在不同溶剂中吸收光谱和荧光光谱的研究

本工作测定了水杨酸和水杨酸甲酯在不同溶剂中的吸收光谱和荧光光谱,并按在不同温度下测得的结果计算出它们在不同溶剂中平衡过程的函变△H.数据表明,在质子溶剂中,上述化合物有较小的△H值,即形成的分子内氢键只有较低的稳定性.根据这些结果可对该类化合物在不同溶剂中形成内氢键的能力作出恰当的评价.     

聚苯胺在一些有机溶剂中溶解性

本文通过改变反应条件用化学方法制得了不同分子量的聚苯胺，考察了它们在有机溶剂中的溶解性．实验结果表明：分子量的大小是影响它们在有机溶剂中溶解度的主要因素，能在有机溶剂中溶解的只是聚苯胺中分子量较小的级分．我们还用聚苯胺（［η］＝０．４９ｄｌ／ｇ）与－ＣＯＣＩ封端的果对苯二甲酰对苯二胺（ＰＰＴＡ）进行嵌段共聚，经过产物的元素分析与计算结果比较，确定出特性黏数为０．４９ｄｌ／ｇ的聚苯胺平均分子量．     

氢气在混合溶剂丙酮-水中的溶解度

本文报导一种能准确测定气体在混合溶剂中溶解度并能同时测定溶剂的饱和蒸气压的实验装置, 在20～40 ℃的温度范围内, 分别测定了氢气在丙酮、水和混合溶剂丙酮-水中的溶解度, 及其相应的蒸气压。     

醇类在惰性溶剂中的缔合溶液热力学

用Kretschmer-Wiebe模型结合Hildebrand-Scatchard公式处理含醇体系的活度系γ_i,得到醇类的自身缔合平衡常数K_A和氢键生成焓h_A。在烷烃溶剂中,K_A与烷烃的碳原子数关系不显著。在同一溶剂中,K_A依下列顺序减小: 甲醇>乙醇>正丙醇>正丁醇; 正丙醇>异丙醇; 正丁醇>异丁醇>仲丁醇>叔丁醇。所测醇类的h_A的平均值为:k_A=-24.3±0.6kJmol~(-1),与醇类的碳原子数及异构关系不显著计算出醇类-角鲨烯体系偏离Hildebrand-Scatchard公式的相互作用常数l_(AB),l_(AB)均为负值,|l_(AB)|依下列顺序减小: 甲醇>乙醇>正丙醇>正丁醇; 正丙醇>异丙醇; 正丁醇>异丁醇>仲丁醇>叔丁醇     

ULTRAFILTRATION MEMBRANE FORMATION OF PES-C, PES AND PPESK POLYMERS WITH DIFFERENT SOLVENTS

Ultrafiltration membranes were prepared using phenolphthalein polyarylethersulfone (PES-C),polyethersulfone (PES) and poly(phthalazinone ether sulfone ketone) (PPESK) as polymers and NMP,DMAc,DMF and DMSO as solvents by immersion precipitation via phase inversion.Experimental data of thermodynamic properties of the polymer solutions and kinetic process of membrane formation were reported.For polymer solutions with good solvents,the sequence of the viscous flow activation energy (E_η) was coincident with ...     

盐卤硼酸盐化学——Ⅶ.盐卤在天然冷冻析盐过程中硼酸盐的行为

某硼酸盐盐湖卤水经日晒蒸发到不同析盐阶段,分别取泻盐和钾盐饱和卤水在实验盐田中储存越冬。前者在天然冷冻析出泻盐之后,当卤水中硼含量达到1.69％MgB_4O_7,温度为-21℃时开始结晶析出MgO·3B_2O_37 1/2H_2O。对于后者,当硼含量为2.43％MgB_4O_7,温度为-17℃时开始结晶析出MgO·3B_2O_3·7 1/2H_2O。     

甲壳素良溶剂及其应用

甲壳素是一种非常重要的高附加值生物质资源,由于无法溶于水、稀酸、稀碱和一般的有机溶剂,极大地限制了其广泛应用。目前寻找合适的甲壳素良溶剂仍是一个非常具有挑战性的课题。国内外文献中尚无专门的甲壳素溶剂方面的综述文章。本文综述了甲壳素的常用良溶剂,包括无机盐、浓酸、浓碱、氟化试剂和酰胺/氯化锂等溶剂。期望为甲壳素的深入研究和利用提供基础的文献参考。     

直接测定单线态氧在溶液中的寿命

单线态氧分子在许多光生物和光化学过程中起重要作用,它在液相中的化学和动力学性质及发光寿命一直为化学家和生物学家所关注.单线态氧通过辐射跃迁回到基态时的两个途径为~1△g(v′=0)→~3∑_g~-(v=0)和~1△g(v′=0)→~3∑_g~-(v=1).(0,1)的发射强度比(0,0)约弱60倍,因此人们一般对(0,0)跃迁感兴趣.O_2(~1△g)的量子产率极低,在水和两亲分子溶液中只有10~(-6).以前由于近红外探测器件的灵敏度不能适应如此微弱磷光强度的检测,故对单线态氧在溶液中的许多物理和化学性质都是用间接测定结果来表征的,例如用二甲基呋喃等O_2(~1△g)捕获剂来证明其存在.近十年来国外开始采用灵敏度高、响应快的锗光电二极管来探测单线态氧的1270nm磷光.关于O_2(~1△g)在液相中的1270nm磷光寿命文献值差异很大;国内则尚未见报道.本文报道我们利用国产锗光电二极管测定单线态氧1270nm发射在一些溶液中的寿命.     

聚二甲基硅氧烷在混合溶剂中的粘度和光散射

用Elias沉淀点法求取聚二甲基硅氧烷25℃在乙苯-邻苯二甲酸二乙酯体系,庚烷-二氧六环体系的θ-溶剂组成。测定了聚二甲基硅氧烷八个级份在甲苯溶液中光散射和两种θ-溶剂中特性粘数,得到 [η]_θ=7.62×10~(-2)(?)_ω~(0.50)乙苯-邻苯二甲酸二乙酯体系γ_ω=19.0％ [η]_θ=8.28×10~(-2)(?)_ω~(0.50)庚烷-二氧六环体系γ_ω=77.2％ 聚二甲基硅氧烷分子无扰尺寸存在溶剂介质依赖性。     

KCl在甲醇-非电解质的混合溶剂中溶解度和溶剂化

本文测定了5、15、25和35 ℃时KCl在甲醇-苯、甲醇-甲苯、甲醇-环己烷和甲醇-四氯化碳中的溶解度S, 并得到经验公式: logS=a+bT, 其中T为绝对温度。同时计算了KCl由甲醇到甲醇混合溶剂的标准迁移自由能ΔG_(tr)~°-, 并得到它和组成x_(Ne)的经验关系式; ΔG_(tr)~°-=CX_(Ne)。同时指出在本实验范围内,温度的变化不影响单纯溶剂化模型和第二介质常数公式的适用性。