高分子光稳定剂的研究——溶解度参数与光稳定效率的关系

<正> 添加光稳定剂是阻止聚合物因光照氧化降解,延长聚合物制品的使用寿命的有效方法。显然只有当光稳定剂能最大程度地均匀分散在聚合物中才能充分地发挥它的光稳定效率,这对高分子光稳定剂来说尤为重要。 光稳定剂与被稳定的聚合物的相容性对光稳定效率的影响已有过研究。如Ambrovic等曾经报道:随着2-羟基4-烷氧基二苯甲酮中烷基的碳原子数增加,它对聚丙烯的光稳定效率提高。高分子光稳定剂本身是一个有一定分子量的聚合物,使用时它与被稳定聚合物形成了共混体系。我们研究了高分子光稳定剂的溶解度参数和它对聚丙烯的光稳定效率的关系。     

苯乙烯-4-(甲基丙烯酸)2,2,6,6-四甲基哌啶醇酯共聚物光稳定能力的初步评价

<正> 2,2,6,6四甲基哌啶类受阻胺化合物是一类新型的光稳定剂。由于它们都有较低的离子化电位,因此有着较强的猝灭单线态氧的能力。在猝灭单线态氧的过程中哌啶基可氧化生成稳定的氮氧自由基,这种稳定自由基可以再进一步在高分子光稳定中起到作用。它能清除高分子降解或氧化过程中产生的能引起高分子进一步降解的活性自由基,以及通过其它途径起到稳定作用。     

β-二酮化合物光稳定行为的研究

研究了β-二酮类化合物二苯甲酰甲烷、苯甲酰丙酮、对苯二甲酰乙酸乙酯的光稳定行为,在β-二酮类化合物的溶液中存在着烯醇式和酮式平衡。当以紫外光进行辐照时,烯醇式异构体不断减少,酮式的含量则不断增多。由于这些化合物有不同的互变异构化过程以及不同的氢键形成能力,因此,它们对高聚物有着不同的稳定化能力。我们提出的二苯甲酰甲烷的光稳定机理,不同于Otterstedt提出的机理。新的统一的光稳定机理尚待进一步深入研究.     

β-二酮类化合物的光互变异构化反应

对三种β-二酮类化合物的光异构化反应进行了研究,并对它们在光照后产生单重态氧的能力进行了测定。该类化合物产生单重态氧的能力与其光异构化为酮式结构的能力成正比,因此凡易于进行光酮化反应的体系,可作为光敏化剂,而不易于进行该反应者,可作为光稳定剂。     

1,2,2,6,6-五甲基哌啶醇对聚丙烯光稳定作用的研究

<正> 关于受阻胺类光稳定剂的稳定作用机理,是近年来光稳定研究领域中广泛探讨的课题,我们用异辛烷溶液研究了1,2,2,6,6-五甲基哌啶醇的光稳定作用,结果已在前文报道,本工作是上述研究的继续,主要研究五甲基哌啶醇对聚丙烯膜的光稳定作用。     

3-芳甲酰基香豆素类化合物光引发聚合的研究

<正> 近年来,3-芳甲酰基香豆素类化合物,作为有效的用于高分子光引发交联的光敏剂和光共引发剂已受到重视,Williams等曾对这类化合物在高分子薄膜中的聚合能力进行了研究,认为其作为光敏剂效果甚佳。本文研究了光敏剂(scn.1)-三乙胺(TEA)体系引发甲基丙烯酸甲酯(MMA)的光聚合,通过与二苯酮(BP)-TEA体系比较,指出了前者具有更高的引发效率,并从光引发聚合体系中光敏剂的激发态性质揭示了这一过程     

硅醚-有机铝体系引发氧化环己烯光开环聚合

<正> 环氧化合物的光开环聚合一般采用正离子光引发剂,常用的有重氮盐、硫鎓盐和碘鎓盐。它们在光照下产生Lewis酸引发环氧化合物开环聚合,由于Lewis酸对金属有强的腐蚀性,从而限制了它们在光固化涂料的应用。 近年,Hayase等报道了一种新型光引发剂,是由硅醚和有机铝组成,用它固化端基     

含氟β-二酮类化合物在质子溶剂中光稳定机理的研究

本工作利用吸收光谱及核磁共振氢谱的方法对两种含-CF₃基的β-二酮类化合物在质子溶剂中引起分子内氢键的破坏,缩醛化的发生及其动力学等进行了研究。工作探讨了光照使缩醛化产物回复至原有的分子内氢键结构以及回复后体系在暗场下继续进行缩醛化的过程,虽然光照使缩醛化产物破坏的原因尚待进一步研究,但这类含有-CF₃基的β-二酮类化合物在光照条件下能回复到含有分子内氢键的体系,这一特性可使这类化合物用作一种能在质子溶剂中应用的光稳定剂。其光稳定能力在本工作中已被证实。     

α,ω-双(4-甲基香豆素)长链化合物的光二聚反应

有关α,ω-双香豆素长链化合物的分子内光二聚反应,在不同极性溶剂中均发生反应的事实,使人们考虑到有可能在非极性溶剂中使带有阻碍基团的4-甲基豆素也易发生光二聚反应。为此我们以三缩四乙二醇为支撑体合成了α,ω-双(4-甲基香豆素)长链化合物,并研究了它的光二聚反应。     

2-[2,4-二羟基苯甲酰]苯甲酸金属盐的合成、表征及其光稳定能力研究

本工作合成了多种含不同过渡金属离子的络合物——2-[2,4-二羟基苯甲酰]苯甲酸钴、镍、锰金属盐.对它们进行了详细表征和光稳定能力进行了实际评价,结果表明这类化合物有很好的光稳定能力,并指出含锰离子的络合物具有最佳光稳定能力是由于锰离子对原有的分子内氢键结构破坏最小所致.     

SYNTHESIS AND EVALUATION OF A NEW PHOTOSTABILIZER—2, 2, 6, 6-TETRAMETHYL-4-PIPERIDINYL SALICYLATE FOR POLYMERS

A new photostabilizer--2,2,6,6-tetramethyl-4-piperidinylsalicylate (TMPS) has been syn-thesized by ester-exchange reaction between 2,2, 6, 6-tetramethyl-4-piperidinol and methylsalicylate.The photostabilizing effect of TMPS and Tinuvin 770, PDS on the photodegradation of cis-1,4-polybutadiene has been investigated for comparison. The results observed show that the mosteffective stabilizer of the three is TMPS. The reason of the good photostabilizing effect of TMPSwas discussed by fluorescence spectra.     

Reactivity and equilibrium thermodynamic studies of rhodium tetrakis(3,5-disulfonatomesityl)porphyrin species with H2, CO, and olefins in water

Aqueous (D2O) solutions of tetrakis(3,5-disulfonatomesityl)porphyrin rhodium(III) aquo/hydroxo complexes ([(TMPS)Rh(III)(D2O)2]-7 (1), [(TMPS)Rh(III)(OD)(D2O)]-8 (2), and [(TMPS)Rh(III)(OD)2]-9 (3)) react with hydrogen (D2) to form an equilibrium distribution with a rhodium hydride ([(TMPS)Rh-D(D2O)]-8 (4)) and a rhodium(I) complex ([(TMPS)Rh(I)(D2O)]-9 (5)). Equilibrium constants (298 K) are measured that define the distribution for all five of these (TMPS)Rh species in this system as a function of the dihydrogen (D2) and hydrogen ion (D+) concentrations. The hydride complex [(TMPS)Rh-D(D2O)]-8 is a weak acid in D2O (Ka(298 K) = 4.3 x 10(-8)). Steric demands of the TMPS porphyrin ligand prohibit formation of a Rh(II)-Rh(II)-bonded complex, related rhodium(I)-rhodium(III) adducts, and intermolecular association of alkyl complexes which are prominent features of the rhodium tetra(p-sulfonatophenyl)porphyrin ((TSPP)Rh) system. The rhodium(II) complex ([(TMPS)Rh(II)(D2O)]-8) reacts with water to form hydride and hydroxide complexes and is not observed in D2O. The (TMPS)Rh-OD and (TMPS)Rh-D bond dissociation free energies (BDFE) are virtually equal and have a value of approximately 60 kcal mol(-1). Reactions of [(TMPS)Rh-D(D2O)]-8 in water with CO and olefins produce rhodium formyl and alkyl complexes which have equilibrium thermodynamic values comparable to the values for the corresponding substrate reactions of [(TSPP)Rh-D(D2O)]-4.     

Spectroscopic studies of trimetoxypropylsilane and bis(trimethoxysilyl)ethane sol-gel coatings on aluminum and copper

Trimethoxypropylsilane (TMPS) and bis(trimethoxysilyl)ethane (BTMSE) were used as surface modifiers of metal vie the sol-gel process and dip coating. In addition to the single coating of Al, Cu and Sn, double treatments of Al were also conducted by combining coatings with these sol-gels in different sequences. Reflection and absorption infrared spectroscopy (RAIR) was employed to characterize and to trace the proceeding of the sol-gel process of the films. It was found that the silanol condensation occurs in the coating films on Al and the covalent linkage exists between the TMPS film and copper surface. From the assigned vibration modes, two conformers were identified in pure TMPS, TMPS sol-gel and coated film. A series of dip coating experiments with different concentrations of TMPS sol-gel was conducted, and the results from the collected RAIR spectra of the coated samples suggested that the coated Cu consistently has a better RAIR spectrum than that of the coated Al. The TMPS sol-gel appeared to have a better affinity to Cu than to Al. The temperature effect and the aging effect in the coating films were studied. X-ray photoelectronic spectroscopy (XPS) was employed to characterize the coated film, and the XPS data confirm the formation of the siloxane film from the silane coupling agents (SCA). Electrochemical impedance spectra (EIS) have been collected for bare Al and Cu, BTMSE sol-gel coated Al, and TMPS sol-gel coated Cu in 0.15M NaCl solution. The corresponding electronic circuit parameters have been determined to match the experimental EIS data.     

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II,Their Reactivity toward Organic Substrates,and the Influence of N‐Methylimidazole Axial Ligation

High‐valent iron‐oxo species have been invoked as reactive intermediates in catalytic cycles of heme and nonheme enzymes. The studies presented herein are devoted to the formation of compound II model complexes, with the application of a water soluble (TMPS)Fe^III(OH) porphyrin ([meso‐tetrakis(2,4,6‐trimethyl‐3‐sulfonatophenyl)porphinato]iron(III) hydroxide) and hydrogen peroxide as oxidant, and their reactivity toward selected organic substrates. The kinetics of the reaction of H₂O₂ with (TMPS)Fe^III(OH) was studied as a function of temperature and pressure. The negative values of the activation entropy and activation volume for the formation of (TMPS)Fe^IV?O(OH) point to the overall associative nature of the process. A pH‐dependence study on the formation of (TMPS)Fe^IV?O(OH) revealed a very high reactivity of OOH^? toward (TMPS)Fe^III(OH) in comparison to H₂O₂. The influence of N‐methylimidazole (N‐MeIm) ligation on both the formation of iron(IV)‐oxo species and their oxidising properties in the reactions with 4‐methoxybenzyl alcohol or 4‐methoxybenzaldehyde, was investigated in detail. Combined experimental and theoretical studies revealed that among the studied complexes, (TMPS)Fe^III(H₂O)(N‐MeIm) is highly reactive toward H₂O₂ to form the iron(IV)‐oxo species, (TMPS)Fe^IV?O(N‐MeIm). The latter species can also be formed in the reaction of (TMPS)Fe^III(N‐MeIm)₂ with H₂O₂ or in the direct reaction of (TMPS)Fe^IV?O(OH) with N‐MeIm. Interestingly, the kinetic studies involving substrate oxidation by (TMPS)Fe^IV?O(OH) and (TMPS)Fe^IV?O(N‐MeIm) do not display a pronounced effect of the N‐MeIm axial ligand on the reactivity of the compound II mimic in comparison to the OH^? substituted analogue. Similarly, DFT computations revealed that the presence of an axial ligand (OH^? or N‐MeIm) in the trans position to the oxo group in the iron(IV)‐oxo species does not significantly affect the activation barriers calculated for C?H dehydrogenation of the selected organic substrates.     

Radiationless decay in the region of the 2t2g and 4eg resonances in SF6

The S 2p Auger spectrum of SF(6) has been studied in the region of the 2t(2g) and 4e(g) resonances. The partial Auger spectra due to the ionization of the 2p spin-orbit components and of a shake-up satellite state have been measured selectively by tuning the photon energy and using the Auger electron-photoelectron coincidence technique. A detailed analysis of the Auger spectrum has also been performed using the Green's function-based second-order algebraic diagrammatic construction method.     

Formation and reactivity of a porphyrin iridium hydride in water: acid dissociation constants and equilibrium thermodynamics relevant to Ir-H, Ir-OH, and Ir-CH2- bond dissociation energetics

Aqueous solutions of group nine metal(III) (M = Co, Rh, Ir) complexes of tetra(3,5-disulfonatomesityl)porphyrin [(TMPS)M(III)] form an equilibrium distribution of aquo and hydroxo complexes ([(TMPS)M(III)(D(2)O)(2-n)(OD)(n)]((7+n)-)). Evaluation of acid dissociation constants for coordinated water show that the extent of proton dissociation from water increases regularly on moving down the group from cobalt to iridium, which is consistent with the expected order of increasing metal-ligand bond strengths. Aqueous (D(2)O) solutions of [(TMPS)Ir(III)(D(2)O)(2)](7-) react with dihydrogen to form an iridium hydride complex ([(TMPS)Ir-D(D(2)O)](8-)) with an acid dissociation constant of 1.8(0.5) × 10(-12) (298 K), which is much smaller than the Rh-D derivative (4.3 (0.4) × 10(-8)), reflecting a stronger Ir-D bond. The iridium hydride complex adds with ethene and acetaldehyde to form organometallic derivatives [(TMPS)Ir-CH(2)CH(2)D(D(2)O)](8-) and [(TMPS)Ir-CH(OD)CH(3)(D(2)O)](8-). Only a six-coordinate carbonyl complex [(TMPS)Ir-D(CO)](8-) is observed for reaction of the Ir-D with CO (P(CO) = 0.2-2.0 atm), which contrasts with the (TMPS)Rh-D analog which reacts with CO to produce an equilibrium with a rhodium formyl complex ([(TMPS)Rh-CDO(D(2)O)](8-)). Reactivity studies and equilibrium thermodynamic measurements were used to discuss the relative M-X bond energetics (M = Rh, Ir; X = H, OH, and CH(2)-) and the thermodynamically favorable oxidative addition of water with the (TMPS)Ir(II) derivatives.     

Über das Jod(V,VII)-oxid J2O6

On the Iodine(V, VII) Oxide I₂O₆ The existence of the compound I₂O₆ is confirmed. It has been prepared by dehydration of a solution of H₅IO₆ and HIO₃ in 95% H₂SO₄ by addition of oleum. Following an earlier method the compound has also been obtained by thermal decomposition of H₅IO₆. I₂O₆ is a chemical species as concluded from its individual Raman spectrum. Diamagnetism proves the formulation as a mixed-valence iodine(V, VII) oxide. According to the vibrational spectrum the compound is nearly described as an iodyl periodate IO₂⁺IO₄^?.     

Vibrational and electronic absorption spectra of 4-chloro 2-methyl, 4-chloro 3-methyl and 6-chloro 3-methyl phenols

The infrared spectra of 4-Cl 2-Me, 4-Cl 3-Me and 6-Cl 3-Me phenols have been recorded. The vibrational spectrum has been analysed assuming that the molecules belong toC _s point group and a tentative assignment of the observed frequencies to various modes of vibration has been proposed. The near ultraviolet absorption spectrum of these compounds has also been recorded. Assuming the transition to be electronically allowed the strongest band on the longer wavelength side has been assigned as the (0, 0) band in each case. The spectrum has been analysed in terms of several excited state frequencies which have been correlated with the ground state frequencies observed in the infrared spectrum.     

Spectroscopic and structural studies of the complex of [Cu6(bpy)10(mu-CO3)2(mu-OH)2](ClO4)6 . 4H2O

The electronic absorption spectrum (diffuse reflection spectrum) of the crystal of [Cu6(bpy)10([mu-CO3)2(mu-OH)2](ClO4)6 . 4H2O has been measured. The experimental results are discussed quantitatively with ligand field theory and the radial wave function of non-free copper(II), and calculation values agree well with the experimental results. The d-d absorption spectrum of a novel hexanuclear copper(II) complex was explained satisfactorily. Especially, complexity of multinuclear crystal structures determined that of spectral behaviors. It provides significant to grope spectral nature from coordination structures.     

Preparation and coordinating properties of {CH2(o-C6H4CH2SbMe2)}2, a novel wide-angle cis-chelating distibine

The unique wide-angle distibine, {CH2(o-C6H4CH2SbMe2)}2, has been prepared indirectly by reaction of Me2SbCl with the di-Grignard formed unexpectedly by coupling of o-C6H4(CH2MgCl)2 in concentrated thf solution, and directly by treatment of the {CH2(o-C6H4CH2MgCl)}2 with Me2SbCl. The very oxygen-sensitive distibine has been characterised by 1H and 13C{1H} NMR spectroscopy and high-resolution EIMS. Oxidation of with Br2 gives the air-stable tetrabromide {CH2(o-C6H4CH2SbMe2Br2)}2. Surprisingly, shows a very strong tendency to function as a cis-chelate, e.g. to Pt(IV) in the complex [PtMe3I], forming an 11-membered ring and providing a stable Pt(IV) stibine complex, the crystal structure of which shows the Sb-Pt-Sb angle to be 95.96(1) degrees. The yellow Pt(II) complex [PtCl2] is obtained from reaction of [PtCl2(MeCN)2] with and IR spectroscopic data and a crystal structure determination confirm the Cl ligands are mutually cis in this species. Reaction of [W(CO)4(piperidine)2] with in refluxing EtOH gives [W(CO)4], the IR spectrum of which shows four nu(CO) bands, also consistent with cis-Sb2 coordination. The cis-chelation is also confirmed by single-crystal X-ray structure determinations of two polymorphs of [W(CO)4].