高氯乳剂的稳定剂和防灰雾剂

本文综述了有关高氯乳剂稳定剂和防灰雾剂概况,尤其是近 20年的文献报道.主要介绍了杂环化合物和磺酸盐化合物这两大类稳定剂和防灰雾剂,其中较为详细地分述了氮杂茚类和含巯基类杂环化合物作为稳定剂和防灰雾剂在高氯化银乳剂中的应用.     

混合银盐的光敏热成像材料感光性能研究

本文以原位法合成的AgBrI作为光敏剂,亲水型的聚乙烯醇为粘合剂,考察了以苯并三氮唑银和4-羟基-6甲基-1,3,3a,7-四氮茚银混合银盐为银源的光敏热成像材料的感光性能,实验结果表明:含AgTAI的混合银盐的PTG材料感光性能明显好于单纯AgBTA的PTG材料.通过光敏热成像材料乳液pH值pAg值测定及银盐DSC分析,认为混合银盐能够提高PTG材料感光性能的原因是其溶解度比AgBTA的溶解度大,能够提供充足的Ag⁺,增大显影密度,提高反差,且混合银盐颗粒尺寸小,其比表面积大,能够充分接触超细卤化银颗粒,从而促进热显影的进行.     

一些含硫、含氮化合物在卤化银成像过程中的作用

采用在曝光前后用不同浓度的化合物溶液分别处理硫增感立方乳剂样品方法,观察它们在感光特性上的差别,从而判断这些化合物在卤化银成像过程的不同阶段各自所起的作用.本工作中所选用的化合物有-1-苯基-5-巯基四氮唑(PMT),6-硝基苯并咪唑-(硝酸盐-),5-硝基苯并咪唑,5-硝基吲唑,4-羟基-6-甲基-1,3,3a,7-四氮茚-(TAI)和硫代乙酰胺.结果表明:PMT在一定的浓度范围内对潜影的形成有促进作用,但对显影有抑制作用;6-硝基苯并咪唑和-5-硝基苯并咪唑的情况相似,对潜影的形成无显著影响,而对显影的抑制作用明显;5-硝基吲唑不仅对潜影的形成有明显阻滞作用,而且对显影也有抑制作用;TAI则对潜影的形成有明显的促进作用,对显影的影响较小;硫代乙酰胺在弱酸性介质中对潜影的形成有显著阻滞作用,对显影也有一定的抑制作用,但对灰雾的增长十分显著.     

4-羟基-6甲基-1,3,3a,7-四氮茚的离解常数和其银盐溶度积的测定

自1935年Birr^[1]发现4-羟基-6-甲基-1,3,3a,7-四氮茚(TAI)作为乳剂稳定剂以来,许多人对TAI的性质和其用途进行了相关的研究.如G.P.FAERMAN[2]等人利用TAI作为防灰雾剂;I.H.Leubner[3]等人利用TAI作为物理成熟抑制剂;许多人还把TAI加在乳化阶段以影响AgX微晶的结构和颗粒分布.     

冠醚对溴化银乳剂的增感作用

近年来,已有将冠醚化合物用于卤化银感光乳剂中的一些报道^[1-4]。为了改善卤化银感光材料的性能,我们将合成的一种新冠醚——N-对甲苯磺酰基-7-氮杂-1,4,10,13-四硫杂环十六烷(NTsTTH)用于卤化银乳剂中,发现它能提高卤化银乳剂的感光度。     

不同表面活性剂反胶束对纳米AgCl性能的影响

在反胶束中研究了直径10～14nm的AgCl微粒子与曙红间的作用,比较了阴离子型和非离子型表面活性剂组成的反胶束微环境效应.考察了AgCl粒子对曙红吸收光谱、荧光光谱及荧光寿命的影响.讨论了AgCl粒子对曙红荧光猝灭的机制,初步研究了稳定剂苯基巯基四氮唑及四氮茚对曙红-AgCl粒子反胶束体系的影响.     

羟基四氮茚在氯化银乳剂中的超增感作用

我们在前文中^[1]报道了轻基四氮茚化合物(以下简称TAI)对氯化银乳剂感光性能的影响,发现它不仅能提高硫增感氯化银乳剂的感光度,而且也能提高未经硫增感的氯化银乳剂的感光度,同时,还能抑制灰雾的增长.通过对其增感机理的研究表明:TAI增感作用不是发生在显影阶段,而是发生在潜影形成阶段.由于TAI的吸附成盐作用,降低了乳剂的间隙银离子浓度及影响了颗粒表面的空间电荷分布导致了增感作用的发生^[2].     

羟基四氮茚在氯化银乳剂中的增感作用

自Birr发现三氮茚和四氮茚类化合物^[1]及其用作卤化银感光剂的稳定剂以来,它们一直受到广泛的关注^[2]。     

稳盐对扁平卤化银微晶增感中心大小和分布的影响

5-甲基-7-羟基-1,3,4三氮吲哚嗪(简称稳盐TAI)作为乳剂制备过程的有机稳定剂,已得到广泛应用.一些作者发现,稳盐除了作为稳定剂之外,对部分乳剂还有增感作用.Tani^[1]在硫敏化的立方体溴化银乳剂中加入稳盐,发现可使乳剂的感光度成倍增加,而稳盐对扁平颗粒和八面体颗粒的溴化银乳剂的增感效果较小.     

三氮吲哚利嗪对氯化银乳剂光谱增感性能的影响

三氮吲哚利嗪(TAI)是一种常用的银盐感光材料的稳定剂,许多研究表明TAI在化学增感或光谱增感乳剂中具有超增感作用^[1,2],另有报道,它与光谱增感染料两者之间的添加次序对增感效果有很大的影响^[1,6,7].     

光敏热显成像材料概述

本文综述了近十多年来国际感光界关注热点之一的光敏热显成像材料(Photothermographic materials,简称PTG)的研究情况.重点介绍了羧酸银、卤化银、调色剂、防灰雾剂与稳定剂、光谱增感剂以及粘合剂等PTG材料的主要组分,并对PTG材料成像机理的研究情况进行了评述.     

卤化银乳剂稳定剂及防灰雾剂的作用机理

对近年来文献中关于感光乳剂的稳定剂和防灰雾剂作用机理的研究进行了总结 ,将其归纳成吸附作用、成盐作用和氧化作用等 3种不同的稳定机理     

基于遗传算法的神经网络对难溶硫化物K_(sp)的预测

采用遗传算法训练神经网络的权重系数 ,并将该神经网络用于对 13种难溶硫化物Ksp的预测 ,预测Ksp值和实验Ksp值的相关系数为 0 .9985 7,结果表明基于遗传算法的神经网络用于难溶硫化物Ksp研究的可行性     

SYNTHESIS AND CHARACTERIZATION OF NEW STABILIZERS WITH OPTIMAL MOLECULAR WEIGHT*

Over 2×10~8 tons of polymers are produced every year, and a large portion of polymers faces the degradationproblem. There are many effective methods to protect polymers against degradation and the addition of stabilizers to polymerremains the most convenient and effective way of enhancing polymer life and performance. In this article, a series of effectivestabilizers with optimal molecular weight (MW), including common, monomeric and polymeric stabilizers (antioxidant andlight stabilizer) were synthesized using isocyanation, controlled isocyanation, hydrosilylation, epoxide addition, macro-reaction of stabilizing functional compounds and polymerization of monomeric stabilizers. The structure and performance ofthese new stabilizers were characterized by using IR, NMR, MS, UV-spectra XPS and elemental analysis. The currentdevelopment of stabilizer synthesis was also reviewed.     

REACTIVITY OF EXCITED STATES OF FLAVIN AND 5-DEAZAFLAVIN IN ELECTRON TRANSFER REACTIONS

Abstract— Quenching of the excited states of lumiflavin and 3-methyl-5-deazalumiflavin by methyl-and methoxy-substituted benzenes and naphthalenes in methanol was investigated. The observed difference in the reactivity of acid and neutral lumiflavin triplets is explained thermodynamically by applying the Michaelis cycle, as being due to the higher reduction potential of the acid triplet. In this connection the p K values of lumiflavin triplet (p K ^M= 6.5) and semiquinone (p K ^M= 11.3) have also been determined in methanol. The difference in the reactivity between the singlet and triplet states of lumiflavin is found to be greater as predicted by the difference in excitation energy. The reactivities of the excited states of flavin and 5-deazaflavin differ only slightly in contrast to the marked difference in the ground state reactivities of electron transfer reactions. This is explained in terms of the model of Rehm and Weller. The pH dependence of the electron transfer quenching of 5-deazaflavin triplet was investigated in water, yielding a triplet p K of 2.5. In contrast to the flavin, this triplet p K does not significantly differ from the p K of the 5-deazaflavin ground state. From this, different sites of protonation are deduced for the photoexcited triplet states of flavin and 5-deazaflavin.     

Dispersion polymerization of styrene in supercritical carbon dioxide using monofunctional perfluoropolyether and silicone-containing fluoroacrylate stabilizers

The free radical dispersion polymerization of styrene was carried out in supercritical carbon dioxide (scCO₂) using two different stabilizers. The polymerizations are performed in the presence of poly(heptadecafluorodecyl acrylate-co-tris(trimethylsilyloxy)silyllpropyl methacrylate) p(HDFDA-co-SiMA) and a commercially available carboxylic acid-terminated perfluoropolyether (Krytox^® 157FSL) as polymerization stabilizers. Dry, fine powdered spherical polystyrene particles were produced under optimised conditions. The resulting high yield of spherical and relatively uniform micron-size polystyrene particles were formed utilizing various amounts of p(HDFDA-co-SiMA) random copolymer. However, it was observed that Krytox^® 157FSL was not a good stabilizer as p(HDFDA-co-SiMA) for the dispersion polymerization of styrene. The particle diameter was shown to be dependent on the type of the stabilizer and the weight percent of the stabilizer added to the system. The effect of varying the concentrations of stabilizers and initiator, reaction time and reaction pressure upon the polymerization yield, molar mass and morphology of polystyrene have been investigated.     

The unexpected motional isotropy of the tin atom in a tricoordinate stannylium cation

The dynamics of the metal atom in the recently isolated tricoordinate tin complex tris(2,4,6-triisopropylphenyl)stannylium tetrakis(pentafluorophenyl)borate was examined by temperature-dependent (119)Sn M?ssbauer spectroscopy over the temperature range 90 K < T < 170 K. Contrary to expectation, the metal atom motion in this temperature range is isotropic within experimental error of the M?ssbauer data, and is only moderately anisotropic, even at 293 K, as evidenced by single crystal X-ray diffraction data. The hyperfine parameters at 90 K are completely consistent with trigonal coordination involving sp(2) hybridization of the 5s5p bonding orbitals of tin.     

Hydroxylbenzylthioethers as novel organic thermal stabilizers for rigid PVC

An investigation was carried out on the performances of hydroxylbenzylthioethers employed as organic thermal stabilizers for rigid poly(vinyl chloride). The efficiency of these compounds as thermal stabilizers was evaluated by using Haake polydrive mixer and TGA. The stabilizing efficiency was compared with Ca-Zn soap and methyltin stabilizer. Hydroxylbenzylthioethers exhibit greater efficiency than both of these stabilizers. This is attributed to the ability of these compounds to prevent the formation of polyene sequences. The hydroxylbenzylthioethers-stabilized PVC showed a slightly lower glass transition temperature (T_g) in comparison with the original PVC. Hydroxylbenzylthioethers and epoxidized soybean oil (ESBO) exhibit synergistic effect on the stabilizing effect, when the mass ratios of ESBO to hydroxylbenzylthioethers are less than 0.5.     

ACIDITY DEPENDENCE OF THE ABSORPTION AND FLUORESCENCE SPECTRA OF ISOFLAVONE AND 7-HYDROXYISOFLAVONE

-The pH and H₀ dependence of the absorption and fluorescence spectra of isoflavone and 7-hydroxyisoflavone are reported. Isoflavone is fluorescent in acidic solution only, whereas 7-hydroxyisoflavone is fluorescent in all acidity ranges under investigation. Ground and first excited singlet state p K _a's have been determined spectrophotometrically and fluorimetrically, respectively. Excited state protolytic equilibration processes via a second order reaction (proton gain) are found to be too slow to compete efficiently with fluorescence. This is deduced from the close agreement between the p K _a's of the conjugate acids obtained by absorption and fluorescence titrations. On the other hand, photodissociation of 7-hydroxyisoflavone proceeds faster than its fluorescence decays. The experimental p K _a(S₁) is in fair agreement with the calculated one. 7-Hydroxyisofiavone forms a phototautomer (or exciplex) in the pH 2 to H₀-1 acidity range, which is characterized by its long wavelength emission. Quantum efficiencies are given for isoflavone and 7-hydroxyisoflavone in aqueous solutions of various acidities. Deuteration effects thereon are discussed.