高分子三重态敏化剂的研究 Ⅲ.高分子苯乙酮敏化过程中能量迁移的研究

本工作合成了一组不同组成的聚(苯乙烯-乙烯基苯乙酮)高分子敏化剂,对分子中两组分的含量进行了标定.通过荧光和磷光光谱的研究表明:高分子敏化剂分子中存在着单重态和三重态的能量迁移和 T~*-T~ 湮灭作用.从降冰片二烯光敏异构化为四环烷的反应中发现,苯乙酮摩尔含量为38％的高分子苯乙酮敏化剂具有最大的敏化能力,并对上述诸现象产生的原因进行了分析和讨论.     

高分子三重态敏化剂的研究——Ⅳ.高分子苯乙酮及其衍生物的光谱、磷光量子产率及光敏化光稳定问题的研究

本工作合成和研究了高分子苯乙酮及其衍生物的光谱、磷光量子产率、磷光寿命以及光敏化、光稳定等问题.结果表明高分子光敏化剂和光稳定剂保持着它们原来相应小分子的光化学和光物理行为.高分子敏化剂由于T-T湮灭,分子链中的光敏基团的含量存在一最佳值,此时磷光量子产率最高,敏化效率最好.但高分子光稳定剂则光稳定基团含量愈高光稳定能力愈强.     

高分子三重态敏化剂的研究IV: 高分子苯乙酮及其衍生物的光谱, 磷光量子产率及光敏化光稳定问题的研究

本工作合成和研究了高分子苯乙酮及其衍生物的光谱、磷光量子产率、磷光寿命以及光敏化、光稳定等问题。结量表明高分子光敏化剂和光稳定剂保持着它们原来相应小分子的光化学和光物理行为。高分子敏化剂由于T-T湮灭, 分子链中的光敏基团的存在一最佳值, 此时磷光量子产率最高, 敏化效率最好。但高分子光稳定剂则光稳定基团含量愈高光稳定能力愈强。     

高分子三重态敏化剂的研究IV: 高分子苯乙酮及其衍生物的光谱, 磷光量子产率及光敏化光稳定问题的研究

本工作合成和研究了高分子苯乙酮及其衍生物的光谱、磷光量子产率、磷光寿命以及光敏化、光稳定等问题。结量表明高分子光敏化剂和光稳定剂保持着它们原来相应小分子的光化学和光物理行为。高分子敏化剂由于T-T湮灭, 分子链中的光敏基团的存在一最佳值, 此时磷光量子产率最高, 敏化效率最好。但高分子光稳定剂则光稳定基团含量愈高光稳定能力愈强。     

光敏聚合中含二苯酮基高聚物的引发作用

合成了多种不同分子量和不同二苯酮侧基含量的高分子敏化剂PVB,从紫外吸收光谱及发射光谱的测定结果表明,PVB基本保持小分子二苯酮(BP)的光化学特性。采用PVB与叔胺组成光敏引发体系引发MMA光聚合时,聚合速度(R_ο)与小分子相比增加二倍以上。而且R_p随PVB分子中二苯酮基含量的增加而增加,当PVB分子量提高时引发聚合能力加强,这和高分子敏化剂分子链中高效率的能量传递以及色基的密集分布特性有关。     

药物递送中的高分子原理

药物递送正在逐渐成熟为一门工程科学,主要根据药理学的要求,利用材料科学的基本原理来进行递送体系设计和研究.高分子是药用材料的主要类别,本文以药物一高分子固体分散体和高分子药物为例,讨论了高分子科学中的基本原理,尤其是结构与性能关系,是如何在药物递送研究和设计中得以体现的.另一方面,药物递送领域的发展也对高分子科学提出了...     

高分子玻璃化熵理论研究进展

玻璃化问题的理论描述是凝聚态物理中的重要基础科学研究课题.高分子是研究玻璃化的典型模型体系,其独有的分子特征为发展有效、普适的玻璃化理论提供了新的机遇.构型熵是发展玻璃化理论的一个核心物理量.基于构型熵的模型可追溯至近一个世纪前观察到的熵与动力学关联的实验现象,并且近年来该理论的发展进入了一个新的阶段,特别是在高分子玻璃化的研究中.本文首先对玻璃化经典熵理论的发展进行了回顾,并介绍了高分子玻璃化熵理论的基本框架.之后,从分子细节影响高分子玻璃化的物理机制、热力学标度与活化体积的理论描述和高分子过冷液体的热力学-动力学关系三个方面阐述了本课题组近年来基于高分子玻璃化熵理论的研究进展,重点强调了该理论在理解高分子玻璃化关键问题中的价值和优势.最后,探讨了高分子玻璃化熵理论进一步发展面临的问题与挑战,并且对玻璃化理论研究的未来发展方向进行了展望.     

液晶性树状高分子

对树状高分子进行功能化,使之成为具有特定性能的新型材料是目前很热门的课题,树状液晶就是其中之一.树状高分子长径比很小,似乎难以形成液晶态,但人们已发现多种树状液晶分子,几乎囊括了所有在其他高分子中出现过的液晶相.本文按液晶相分类,介绍树状液晶高分子的研究进展.     

机器学习方法在高分子玻璃化研究中的应用

高分子玻璃的物理性质与其结构和动力学密切相关.揭示高分子玻璃化的微观物理图像对高分子玻璃材料的结构调控和分子设计至关重要.然而,高分子的长链结构和复杂单体结构特征致使目前仍然缺乏普适的理论或者模型来定量解释高分子玻璃化的物理机制.因此,亟需发展更为先进的研究方法从而更深入地理解高分子玻璃化.近年来,国内外学者利用基于数据驱动的信息学方法(例如机器学习)对高分子玻璃化开展了研究,并取得了丰富成果.本综述首先介绍了常用的高分子信息学数据库和机器学习算法.之后,从高分子玻璃化转变温度的预测、新型高分子玻璃材料的研发、过冷液体的结构-动力学关系和玻璃体系相变的确定四个方面总结和评述了机器学习应用在玻璃化研究中的代表性进展.最后,探讨了机器学习方法在高分子玻璃化研究中面临的主要挑战,并对玻璃信息学这一领域的发展进行了展望.     

序列可控高分子的合成及应用

序列可控高分子是指高分子链中不同单体单元按特定顺序排列的高分子.自然界中的生物大分子,如核酸分子和多肽,其精确的序列结构决定了其复杂功能的表达.受此启发,序列可控高分子的合成及序列结构与性能关系研究近年来受到了越来越多的关注.本文介绍了近年来在序列可控高分子合成方面的重要研究成果,突出介绍了本课题组在序列可控高分子方向的研究进展.最后,对序列可控高分子的应用进行了总结和展望.     

氯氰菊酯光敏降解中单线态氧机理研究

光敏剂亚甲兰,核黄素及玫瑰红Ｂ可加速氯氰菊酯（ＣＰＭ）的光解作用。这些物质的敏化作用主要通过激发基态氧为单线态氧来实现。光敏剂和氧均是敏化光降解不可缺陷少的条件。１／Ｋｅｘｐｔｌ与「Ａ」的关系证实了单线态氧氧化机理。在亚甲兰、核黄素存在下氯氰菊酯ＫＡ分别为６．４９＊１０＾６ｌ．ｍｏｌ＾－１．ｓ＾－１和２．２７＊１０＾６Ｌ．＾－１。氯氰菊酯的光解速率在一定范围内,随光敏剂浓度的增加而增加,过量的光敏剂将减少体系的透光率而导致氯氰菊酯光解速率降低,单线态氧探针性物质即竞争反应的引入将明显降低氯氰菊酯的光解速率,同时,不同极性溶剂因其对单线态氧猝灭能力的不同也会明显改变氯氰菊酯的光解速率。     

Photocyclization of iminyl radicals: theoretical study and photochemical aspects

The irradiation of acyloximes was studied by theoretical methods. CASPT2/6-31G*//CASSCF/6-31G* calculations, using an active space of 14 electrons in 11 orbitals, indicate that S2 should be the spectroscopic state, and its relaxation leads directly to N-O bond breakage due to coupling between the imine pi* and the sigma* N-O orbitals. Subsequent calculations at the B3PW91/6-31+G* level suggest that the resulting iminyl radicals are able to cyclize to the five- or six-membered ring, depending on the presence of a phenyl group as a spacer, a process that has been verified experimentally. The photochemical aspects of the more common five-membered ring formation, such as excited-state quenching, quantum yield, excited-state sensitizers, laser flash photolysis experiments, Stern-Volmer plot, and luminescence measurements, were investigated. These studies indicate that singlet and triplet excited states undergo the same reaction. Emission lifetimes of ca. tau = 10.6 micros for compound 11 are suggestive of triplet parentage, while no fluorescence was detected, in agreement with the computed MEP energy profile.     

A solid-state 39K and 13C NMR study of polymeric potassium metallocenes

The quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) and double frequency sweep (DFS)/QCPMG pulse sequences are applied in order to acquire the first solid-state 39K NMR spectra of organometallic complexes, the polymeric main group metallocenes cyclopentadienyl potassium (CpK) and pentamethylcyclopentadienyl potassium (Cp*K). Piecewise QCPMG NMR techniques are used to acquire a high S/N 39K spectrum of the broad central transition of Cp*K, which is ca. 200 kHz in breadth. Analytical and numerical simulations indicate that there is a significant quadrupolar interaction present at both potassium nuclei (C(Q)(39K) = 2.55(6)/2.67(8) MHz and 4.69(8) MHz for CpK (static/MAS) and Cp*K, respectively). Experimental quadrupolar asymmetry parameters suggest that both structures are bent about the potassium atoms (eta(Q)(39K) = 0.28(3)/0.29(3) for CpK (static/MAS) and eta(Q)(39K) = 0.30(3) for Cp*K). Variable-temperature (VT) 39K NMR experiments on CpK elucidate temperature-dependent changes in quadrupolar parameters which can be rationalized in terms of alterations of bond distances and angles with temperature. 13C CP/MAS NMR experiments are conducted upon both samples to quantify the carbon chemical shielding anisotropy (CSA) at the Cp' ring carbon atoms. Ab initio carbon CSA and 39K electric-field gradient (EFG) and CSA calculations are conducted and discussed for the CpK complex, in order to correlate the experimental NMR parameters with molecular structure in CpK and Cp*K. 39K DFS/QCPMG and 13C CP/MAS experiments prove invaluable for probing molecular structure, temperature-dependent structural changes, and the presence of impurities in these systems.     

硫代苯甲酸-S-苯酯敏化光解的研究

本文对硫代苯甲酸-S-苯酯类化合物的敏化光解反应进行了研究, 以图扩大其光谱响应范围。工作表明硫代苯甲酸-S-苯酯能与芘、北等敏化剂发生电子转移反应, 并进而促使硫代苯甲酸-S-苯酯分子裂解, 产生各种分解产物; 气相色谱-质谱联用仪分析结果表明, 敏化光解产物主要为苯甲醛和二苯基二硫醚,在此基础上对标题化合物敏化光解的机制提出了看见。此外, 从该光敏体系能引发甲基丙烯酸甲酯聚合进一步表明, 硫代苯甲酸-S-苯酯能与适宜的电子给体组成光敏引发体系, 使该体系的光敏引发可用波长扩展到400nm以上。     

Fluorescence quenching study on the interaction of bases of nucleic acid with electron-accepting sensitizer and serum albumin containing electron-rich tryptophan residue

Static and dynamic fluorescence quenchings of electron-accepting sensitizers including positive charged heterocyclics and neutral cyanoaromatics by bases of nucleic acid (NB) have been investigated. It was found that NB could act as effective electron donors to quench the fluorescence of electron-accepting sensitizers. The quenchings by diffusion-controlled rate coincide well with the static and dynamic Stern-Volmer correlation. On the other hand, the diffusion-controlled fluorescence quenchings of the tryptophan (TRP) residue in the protein enzymes, HSA and BSA, by electron-accepting NB reveal that photochemical dual-damage of protein enzyme and thymine (THM) occur upon u.v.-irradiation, which is characteristic of excitation wavelength-dependence. Therefore, the results illustrate that the lesion interactions of NB with electron-deficient sensitizers or electron-rich TRP fluorophore-containing protein enzymes originate mainly from PET-initiated processes in both cases.     

A theoretical study on fullerene-dizincocene hybrids

Using the density functional theory, we investigated the possible formation of fullerene-dizincocene hybrids, specifically C(60)*-Zn-Zn-Cp*, C(60)*-Zn-Zn-C(60)*, C(70)*-Zn-Zn-Cp*, and C(70)*-Zn-Zn-C(70)*, where C(60)*, Cp*, and C(70)* represent C(60)(CH(3))(5), C(5)(CH(3))(5), and C(70)(CH(3))(5) radicals. Our calculation shows that these hybrids have HOMO-LUMO gaps which are larger than has been experimentally identified for C(60)*-Fe-Cp. In addition, the strength of the Zn--Zn bonds is similar to that in Cp*-Zn-Zn-Cp* which was also synthesized recently. Furthermore, heterohybrids, C(60)*-Zn-Zn-Cp* and C(70)*-Zn-Zn-Cp* are expected to exist in equilibria with homohybrids, C(60)*-Zn-Zn-C(60)* and C(70)*-Zn-Zn-C(70)*, in which heterohybrids are much more favored. On the other hand, another hybrid involving Sc(3)N@C(68) as a fullerene unit is not highly probable.     

High pressure studies of isoquinoline luminescence in polymeric media

The fluorescence peak of isoquinoline increases strongly in intensity with increasing pressure in polymethylmethacrylate (PMMA) and in polyisobutylene (PIB). In polyvinylalcohol the intensity decreases as the pressure increases. In all three cases the emission peak shifts to lower energy as the pressure increases. The results are consistent with the hypothesis that the ππ* state lies higher in energy than the nπ* state in non-hydrogen bonding solvents, but that the situation is reversed in hydrogen bonding solvents.     

IS SINGLET OXYGEN FORMATION DOMINANT IN TRIPLET QUENCHING PROCESSES? MEASUREMENT OF THE QUANTUM YIELD OF SINGLET OXYGEN FORMATION BY THE TIME-RESOLVED THERMAL LENS METHOD

The quantum yields of singlet oxygen formation (Ø_Δ) by the quenching of triplet states of organic sensitizers are measured at various concentrations of the sensitizers by using the time-resolved thermal lens method. Above a certain concentration, Ø_Δ is independent of the sensitizer concentration. Below the threshold, Ø_Δ gradually decreases as the concentration of the sensitizer decreases. The extrapolation of Ø_Δ to zero concentration indicates that singlet oxygen formation is not necessarily dominant in the quenching process even for the ³ππ* state in benzene.     

炸药敏化剂的分子结构、电子结构和生成热的理论研究

在HF/6-31G*和B3LYP/6-31G*基组水平上, 对硝酸乙酯(EN)、硝酸正丙酯(NPN)、硝酸异丙酯(IPN)、硝酸异辛酯(EHN)和四甘醇二硝酸酯(TEGDN)五种炸药敏化剂进行理论计算, 研究了标题物的分子结构、电子结构和能量等方面的性质. 基于Mulliken布居和键长分析, 五种硝酸酯分子的热分解始于O2—N3键的断裂, 且由Mulliken电荷分布推知分子热解产生NO2气体. 在分析前线轨道能(EHOMO, ELUMO)和能量差(ΔE)的基础上对五种硝酸酯的相对热稳定性大小进行了评估. 由等键反应获得的EN、IPN、NPN、EHN和TEGDN的标准生成热分别是-155.972、-190.896、-175.279、-272.376和-790.733 kJ·mol-1.