Wavelength sensitivity of the photoinduced reaction in polycarbonate

Bisphenol A polycarbonate (PC) was irradiated with monochromatic light of wavelengths 260, 280, 300, 320, 340, 400, and 500 nm by use of the Okazaki large spectrograph (OLS). The quantum yield of main-chain scission (?_cs), efficiency of photo-Fries rearrangement (E_r), and effects of wavelength on ?_cs and E_r were investigated. It was found that photodegradation and photo-Fries rearrangement of PC took place by the irradiation of 260–300 nm light, but did not by the irradiation at λ ≧ 320 nm. The ?_cs has a maximum value in the case of the irradiation with 260 nm light, while E_r was found to have a maximum value by the irradiation of 280 nm light. © 1993 John Wiley & Sons, Inc.     

Investigation of fullerene C60 effect on properties of polymethylmethacrylate exposed to ionizing radiation

Effect of fullerene C₆₀ was investigated on thermal, mechanical and optical properties of polymethylmethacrylate (PMMA) under ionizing radiation. It was stated that fullerene C₆₀ behaves as an effective antirad with respect to PMMA. Fullerene C₆₀ addition raises temperature of destruction for polymer subjected to electron radiation by 20-25 °C, lowers the rate from 4 to 4.5 times and increases the activation barrier for radiated PMMA destruction reaction. Fullerene C₆₀ addition promotes improvement of strength properties of PMMA: for films containing C₆₀ addition and else subjected to electron radiation treatment a decrease in rupture strength is 10-15%, for samples containing no fullerene it equals ∼25%. Interaction of free radicals with fullerene at radiation treatment influences optical characteristics of PMMA films.     

Density profile of spin cast polymethylmethacrylate thin films

The density profiles of polymethylmethacrylate (PMMA) thin films on silicon (111) single crystal wafers were investigated via neutron reflectivity measurements. Films were prepared by spin casting PMMA onto silicon wafers from o-xylene solution followed by annealing under vacuum at 90°C for 5 h. A ～45 Å thick layer at the free polymer surface was observed in the as-prepared samples that has a density about half the value of bulk PMMA. After heating above 110°C, this diffuse layer disappeared and the thin film density profile was transformed to one with a sharp free polymer surface. This transition was found to be irreversible. © 1994 John Wiley & Sons, Inc.     

芳醚树枝形聚合物的合成及分子内光敏异构化反应研究

利用收敛法合成了一代到四代外围带有二苯酮、核心带有降冰片二烯的芳醚树枝形聚合物, 初步研究了这些化合物的分子内光敏异构化反应. 以波长大于350 nm的光选择激发外围的二苯酮官能团引起核心处降冰片二烯基团异构化为四环烷, 随着代数的增长, 光敏异构化反应的速率逐渐加快.     

Wavelength Flexibility in Photoinitiated Cationic Polymerization

The spectral sensitivity of onium salt photoinitiators in cationic polymerization can be tuned from the short wavelength region of the UV spectrum to wavelengths up to the visible region by using direct and indirect activation, respectively. Indirect activation is based on the electron transfer reactions between onium salts and free radical photoinitiators, appropriate sensitizers and compounds capable of forming charge transfer complexes. Bisacylphosphine oxides, dimanganese decacarbonyl in conjunction with alkyl halides and titanocene type photoinitiators such as Irgacure 784 were shown to be useful free radical promoters providing the possibility of performing cationic polymerization in the long wavelength and visible region. The synthetic routes to prepare block copolymers by using electron transfer photosensitization and free radical promoted cationic polymerization are also described.     

The influence of aliphatic sulfides on the photoinduced polymerization of butanediol-1,4 dimethacrylate

The photoinduced polymerization of butanediol-1,4 dimethacrylate was investigated in the presence of various linear sulfides and cyclic dithioacetals. Benzophenone was used as a sensitizer. It was found that the addition of small amounts of sulfides to the polymerization mixture causes, depending on the sulfide structure and concentration, reduction or full elimination of an induction period as well as an increase in the reaction rate and yield both in air and argon-saturated systems. The explanation of the obtained results is based on the propensity of sulfides to act as hydrogen donors, chain-transfer agents, and highly oxidizable compounds.     

光敏电子转移异构反应中的盐效应

本文利用四正丁基四氟硼酸铵为探针, 研究了顺式芪和四环烷的9,10-二氰基蒽敏化光异构化的反应机理, 加入四正丁基四氟硼酸铵明显加快顺式芪的异构反应而减慢四环烷的反应。荧光猝灭及激光闪光光解实验证明四正丁基四氟硼酸铵能促进电荷分离过程而生成离子自由基对。从而证实顺式芪的异构化反应是经由离子自由基的历程, 而四环烷则是通过激基复合物机理。     

基于颜色主波长与补色波长的比色法定量检测

利用sRGB(Standard RGB)颜色空间与国际照明委员会(CIE)色度系统的转化关系以及CIE 1931色品图的性质,编写MATLAB程序实现了颜色的RGB信息到颜色主波长或补色波长的转化,并将此程序用于分析面光源下采集到的显色产物的图片。利用颜色的主波长实现了对pH值的定量检测,利用颜色的补色波长完成了对亚硝酸根离子的定量检测。当pH值分别在4.0~7.0和7.5~10.0范围内,pH值均与其显色产物颜色的主波长呈线性变化;亚硝酸根离子浓度在10~40 mg/L范围内与其显色产物颜色的补色波长有良好的线性关系,通过结合图片的G值分析,扩大了传统吸收光谱法的检测范围。     

HPLC紫外分光检测器的波长范围、波长准确度和波长重复性及其测试方法的探讨

根据实践,提出了高压液相色谱（HPLC）紫外分光检测器的波长范围、波长准确度和波长重复性等技术指标的具体、简易、可行的测试方法,可供有关设计、制造、使用者参考．     

Synthesis of block and star copolymers by photoinduced radical coupling process

The general design for the synthesis of AB diblock, and A₂B and AB₂ star copolymers based on the statistical coupling of poly(styrene) (PSt) and poly (methyl methacrylate) (PMMA) macromolecules containing photoreactive benzophenone is presented. For this purpose, mono- and bifunctional initiators for Atom Transfer Radical Polymerization (ATRP) bearing benzophenone group were synthesized and characterized. End- and mid-chain benzophenone functional PSt and PMMA with low molecular weights were obtained by ATRP using these initiators in the presence of CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) catalytic complex. Poly(styrene-block-methyl methacrylate) (PSt-b-PMMA) copolymers were prepared by photolysis of the solutions containing end functional PSt and PMMA in THF at λ = 350 nm for 60 min in the presence of a hydrogen donor such as N-methyldiethanolamine (NMDEA). The proposed mechanism assumes hydrogen abstraction of photoexcited benzophenone moiety by NMDEA. Ketyl radicals resulting from abstraction reaction undergo radical-radical coupling to form benzpinacol structure at the core. Formation of A₂B and AB₂ type star copolymers upon irradiation of solutions containing appropriate combinations of end- and mid-chain functional polymers was also demonstrated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2938–2947, 2009     

Efficient photoinduced conversion of an azo dye on hexachloroplatinate(IV)-modified TiO2 surfaces under visible light irradiation-A photosensitization pathway

The titanium dioxide photocatalyst is employed to examine the influence of chemisorbed hexachloroplatinate(IV) anions (PtCl(6) (2-)) on the surface of P-25 TiO(2) particles on the photoinduced conversion of the azo dye Ethyl Orange (EO) in visible light-illuminated Pt(IV)/TiO(2) dispersions. Spin-trap electron spin resonance (ESR) spectral results, measurement of quantities of organoperoxides formed, total organic carbon (TOC) and chemical oxygen demand (COD(Cr)) assays, together with XPS evidence show that the self-sensitized transformation dynamics of the EO dye mediated by Pt(IV)/TiO(2) are much faster than those occurring on naked TiO(2) under otherwise identical conditions of visible light irradiation. X-ray photoelectron spectral data also show that under the experimental conditions used, no Pt(0) formed on the titania particles during visible light irradiation. We propose a reaction mechanism in which the more rapid conversion of EO in the presence of PtCl(6) (2-) is caused principally by photoexcitation of the dye and not by localized excitation of the tetrachloroplatinate(IV)/TiO(2) particles.     

双波长分光光度法测定微量钯的研究

本文报道以２－（３，５－二氯－２－吡啶偶氮）－５二甲氨基苯胺（简称为３，５－ｄｉＣｌ－ＰＡＤＭＡ）为显色剂，应用双峰双波长光度法测定钯的新方法及其钯配合物的质子化行为１．２ｍｏｌ／Ｌ的硫酸介质中，钯与试剂形成稳定的１：１绿蓝色配合物，其最大吸收峰为６２１ｎｍ，负峰为４３４ｎｍ，正，负峰吸光度绝对值之和与钯浓度线性相关，钯浓度在，每１０ｍＬ０～１２μｇ范围内符合比尔定律，表观摩尔吸光系数高达１．４４     

The effect of ions irradiation on the thermal properties of poly(ether ether ketone)

The effect of irradiating amorphous poly (ether ether ketone), PEEK, with ions, 11 MeV proton (H⁺), and 25.6 MeV helium (He²⁺), has been investigated focusing on the changes in thermal properties. The extent of chain scission and crosslinking was evaluated using the Charlesby‐Pinner equation. Crosslinking increased the glass transition temperature (T_g) in line with the DiBenedetto equation from which the crosslinking constant for each ion was calculated. The effect of irradiation on the thermal degradation kinetics was studied in an argon atmosphere at a constant heating rate by mean of the Chang and the second Kissinger methods. Irradiation significantly reduced the thermal stability of the polymer and its service lifetime. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2212–2221, 2008     

单波长可见光照射下二氧化碳羰基化反应研究

近年来 ,由于能源及基本原料短缺问题日益紧迫以及二氧化碳大量排放导致的“温室效应”对人类生存环境及生态平衡影响日益加剧等原因 ,促使二氧化碳化学作为绿色化学的研究内容之一迅速发展起来 .以二氧化碳为碳源与烯烃进行羰基合成也取得了很大进展 [1,2 ] ,但反应一般要求在高温高压下进行或者采用贵金属作为催化剂 .最近 ,利用二氧化碳进行光催化合成羰基化产物也有了一定进展 [3] ,反应条件得到大大改善 .我们[4 ] 曾报道在紫外光照射条件下 ,以 Co(acac) 2 为催化剂二氧化碳与环己烯进行羰基化反应制备环己基甲酸甲酯 ,反应能在常温…     

甲基戊糖的双波长紫外分光光度分析法

对一种甲基戊糖的分光光度法加以改进，采用正交设计法选择实验中试剂量的最佳组合，并分析了测定中相关参数的影响。该法简单、快速、精确、灵敏度高，检测线性范围为2－90mg/L，测量鼠李糖的相对误差为2.6%。文中还以实际发酵液作为分析对象，用高压液相色谱法验证了该检测技术的可靠性。     

薄层色谱扫描仪波长示值误差校准方法

目前我国没有薄层色谱扫描仪国家检定规程,一些地方或部门标准中的波长示值误差项目计量方法可操作性不强。通过对比现有标准,提出了一种薄层色谱扫描仪波长示值误差计量方法。该方法利用计量单位使用的钬玻璃波长滤光片作为计量标准器,操作步骤与样品测试类似,波长示值误差的扩展不确定度为0.6 nm(k=2),满足校准要求。该法降低了计量操作难度,可作为计量人员的参考依据。     

多组分分析的连续波长紫外分光光度法

提出了一种利用紫外光谱连续波长吸光度数据对多组分混合物定量分析的方法:把吸光系数和待测浓度同时作为自变量,优化分析出待测浓度。对多种物系实验数据的分析结果表明,该法稳定、准确度高。     

MPF—4荧光光谱仪波长系统的故障排除

本文介绍了MPF-4荧光光谱仪波长系统的故障分析及排除方法。叙述了波长的校准方法和步骤。     

Effect of crosslinking on the photoinduced orientation of azo groups in thin polymer films

A series of amorphous copolymers containing disperse red 1 and crosslinkable acrylic groups were prepared. The crosslinked polymers were prepared in thin films by thermal polymerization of the acrylic groups in the copolymers. The orientation induced by irradiation with a linearly polarized laser was measured as birefringence at several temperatures, and the effect of crosslinking on the photoinduced orientation was investigated. Crosslinking enhanced the stability of the photoinduced birefringence. In particular, crosslinking helped to maintain the birefringence both at high temperatures and after the linearly polarized laser was turned off. The birefringence dynamics was analyzed with biexponential curve fitting. Crosslinking influenced not only the birefringence levels but also its rate of growth. The growth rate of the photoinduced birefringence decreased by crosslinking, whereas the relaxation was not significantly affected. Although crosslinking restrained the mobility of the azo chromophores, a certain fraction could orient or move randomly even in highly crosslinked polymer networks. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1686–1696, 2001     

苦丁茶中总黄酮的三波长-光谱法定量分析

采用三波长 分光光度法测定苦丁茶中有效化学成分黄酮的含量 ,有效地消除了吸收峰不对称给定量分析能造成的影响 ,并校正了基于干扰组分 (饮料中添加剂等 )的吸收光谱具有可能是散射造成的背景线性吸收产生的基线倾斜。回归方程为 :ΔA =- 3.70 2× 1 0 -3 +3.70 2 3C ,相关系数r =0 .9994 ,黄酮的浓度在6 0 0～ 1 6 0 0mg/L范围内 ,分别在波长为λ1 =4 70nm ,λ2 =4 2 0nm ,λ3 =370nm处测吸光度时 ,则ΔA与浓度C之间呈良好的线性关系 ,可按标准曲线法进行定量分析。方法的回收率为 98%～ 1 1 2 % ,相对标准偏差小于1 1 4 %。方法的准确度与精密度均令人满意 ,而且操作简便易行