光捕获树枝形聚合物体系能量传递和电子转移研究进展

树枝形聚合物是一类围绕着中心核,外围链段和官能团呈指数增长的支化高分子.合成方法的发展使发色团可被精确地置于树枝形聚合物的核心、外围甚至支化节点处.树枝形聚合物的特殊结构使其作为模拟光捕获体系被广泛研究.光诱导电子转移和能量传递是光合作用中的重要过程,研究树枝形聚合物体系中的电子转移和能量传递对未来树枝形聚合物在光电器件中的应用有着重要意义.本文综述了近年来光捕获树枝形聚合物体系的研究进展,并重点介绍光捕获树枝形聚合物体系中的能量传递和电子转移过程研究.     

芳醚树枝形聚合物体系中电子转移和能量传递研究

树枝形聚合物英文名为dendrimer，是具有类似树枝状结构的化合物，由核心、内层支化单元和外围基团三部分组成．树枝形聚合物具有与光合作用体系相似的结构，作为模拟光合作用体系被广泛研究．电子转移是光合作用中的重要过程，研究树枝形聚合物体系中的电子转移与能量传递具有重要的意义．本论文设计合成了一系列芳醚树枝形聚合物，用光物理和光化学方法研究了芳醚树枝形聚合物体系中电子转移和能量传递过程，得到了一系列有意义的结果．具体如下：     

芳醚树枝形聚合物体系的设计合成及电子转移和三重态能量传递研究

树枝形聚合物是一类具有特殊结构的大分子，通过可控合成，具有光捕获功能的官能团可以精确地分布在树枝形聚合物的核心或外围，甚至可以在支化单元的任何位置，随着代数的增加，官能团数目从核心向外围呈指数增长，树枝形聚合物的这种特殊结构被用来模拟光合作用中的光捕获体系．电子转移和能量传递是光合作用的关键过程，也是光化学研究的重要内容，因此，研究树枝形聚合物体系内的电子转移和能量传递是人工模拟光合作用的一个突破口，是目前相关研究工作的热点之一．本文设计合成了一系列一代到四代的芳醚树枝形聚合物，共24个新化合物，通过稳态、瞬态以及光化学反应的方法研究了芳醚树枝形聚合物体系内电子转移和三重态能量传递过程，得到了一系列有意义的研究结果：     

一种新型的交联极化聚合物的合成及性能研究

以成膜性能优异、主链上含有多个羟基的聚双酚A二缩水甘油醚-苯胺（BPAN）为骨架,将二阶非线性光学活性发色团分子以键合形式挂接到聚合物主链上,形成新型侧链型聚合物.此聚合物保留了原聚合物体系成膜性好和可进一步交联等优点.极化过程中以含有异氰酸酯基的同种发色团分子作为交联剂,得到发色团含量进一步提高的交联型极化聚合物.采用衰减全反射法（ATR）测得体系的电光系数（r33）为6.7 pm/V（1315 nm）.     

水溶性树枝形聚合物微反应器笼效应研究

本工作以羧基为末端基团的芳醚树枝形聚合物Gn(n=1—4)和核心为十二烷基链的聚酰胺-胺树枝形聚合物PGm(m=1—3)作为光化学微反应器,研究了1-苯基-3-对甲苯基丙酮在水溶液中的α-光解反应,并计算了笼效应.研究结果表明,芳醚树枝形聚合物Gn的笼效应随代数增加而增大,高代数树枝形聚合物表现出对底物分子更强的限制性作用,增加树枝形聚合物的浓度可以提高笼效应;聚酰胺-胺树枝形聚合物PGm对CH3-DBK的限制作用远低于芳醚树枝形聚合物Gn.     

荧光共轭聚合物的结构设计与合成方法研究

荧光共轭聚合物既有机小分子荧光材料优良的光学品质,又具有高分子材料优越的可加工性能,成为了荧光材料的研究热点。因此,荧光共轭聚合物在开发新型化学、生物及爆炸物传感器等方面具有非常广阔的应用前景。本文介绍了几种典型的荧光聚合物,重点介绍了聚合物中荧光发色团的合成,从分子结构设计、应用及优缺点等方面对各种合成方法进行阐述比较。并且展望了今后荧光共轭聚合物的发展前景。     

聚合型荧光增白剂

聚合型荧光增白剂是由荧光单体与其他单体聚合而成,可解决传统荧光增白剂耐光性差等缺点.简要介绍了聚合型荧光增白剂的分类,讨论了二苯乙烯、萘酰亚胺、芘类聚合型荧光增白剂的合成、结构、性能及应用.聚合型荧光增白剂中基本发色团的结构不变,具有传统荧光增白剂的光学性能;发色团与高分子链间的共价键使其光化学稳定性大大增强,增白性能和荧光量子产率显著提高.聚合型荧光增白剂可应用于纺织品、聚合物材料和洗涤剂,还可用于液晶显示器、荧光探针等高科技领域.开发环保型高性能新产品、不同类型增白剂共混与复配以及多个含不同发色团单体间的聚合有可能成为新的研究热点.     

芳醚树枝形聚合物体系的设计合成以及构象的研究

树枝形聚合物是一类围绕中心核外围链段随着代数的增加以指数级别增长的化合物，它具有高度的几何对称性、精确的分子结构、分子内存在空腔、分子本身具有纳米尺寸等特点．由于其具有精美的结构，树枝形聚合物在高分子、催化、光化学、材料科学等方面具有广泛的应用前景．材料的结构决定它的性能以及应用，为了拓宽树枝形聚合物的应用范围，对其结构以及构象的研究就显得颇为重要．     

萘酰亚胺类高聚物色素研究进展

综述了苯酰亚胺类高聚物色素研究进展,萘酰亚胺结构的特殊性和容易生成多种衍生物,使之成为研究较多的可荧光着色剂单体。烯丙基是这类可聚合色素单体主要的聚合基团．可以在萘酰亚胺分子的不同位置引入,形成多种结构。作为可聚合物单体,萘酰亚胺可以与苯乙烯、丙烯酸酯、丙烯腈等发生共聚反应,得到侧链带有荧光发色团的聚合物,该聚合物可应用于不同高新技术领域。     

红藻条斑紫菜R－藻红蛋白中的能量传递过程

本文通过对条斑紫菜Ｒ－ＰＥ（藻红蛋白）及其α－β－γ亚基的吸收光谱和荧光光谱进行计算机解叠，研究了Ｒ－ＰＥ内发色团之间的能量传递过程，并对Ｒ－ＰＥ及亚基内的各发色团进行了“ｓ”和“ｆ”型的指认。发现在亚基中为“ｆ”型的发色团在Ｒ－ｐＥ（αβ）＿６γ中起着“ｓ”型发色团的作用，且将能量传递给最后的“ｆ”型发色团。荧光激发偏振光谱进一步证明了Ｒ－ＰＥ内的能量转移过程与计算机解叠的结果一致。     

Synthesis,properties, and self‐assembly of poly(benzyl ether)‐b‐polystyrene dendritic–linear polymers

Poly(benzyl ether)‐b‐polystyrene dendritic–linear polymers were successfully synthesized using a dendritic chloric poly(benzyl ether) (G₁‐Cl, G₂‐Cl, and G₃‐Cl) as the macroinitiator through the atom transfer radical polymerization process. The structure and properties of the resultant polymers were characterizated by gel permeation chromatography, ¹H‐NMR, Fourier transform IR, thermogravimetric analysis, and differential scanning calorimetry. It was found that the temperature, reaction time, molar ratio of the macroinitiator to styrene, and the generation number of the macroinitiator have significant effects on the molecular weights, conversion, and polydispersities of the resulting polymers. These dendritic–linear block polymers had very good solubility in common organic solvents at room temperature. The terminal group (dendritic segments) of the polymers can affect their thermal stability. These dendritic–linear polymers after self‐assembling in selective solvents (chloroform/acetone) formed core–shell micelles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1106–1112, 2005     

Poly(amidoamine) dendritic structures,bearing different end groups,as adhesion promoters for urea–formaldehyde wood adhesive system

A series of core‐shell poly(amidoamine) (PAMAM) dendritic compounds bearing different end groups such as  OH, NH₂, and NH₃⁺⁻Cl up to the third generation were prepared via successive Michael addition of a nucleophilic core (ethylenediamine) to methylacrylate followed by amination steps using ethylenediamine for the amine‐terminated while ethanolamine for the hydroxyl‐terminated compounds, also the protonated ammonium salt terminated form was obtained by cationization of the amine‐terminated form using hydrochloric acid solution. The Surface activity and aggregation behavior of the corresponding aqueous solutions of the prepared generations with their different end groups were studied and confirmed by surface tension measurements using ring method technique. The prepared dendrimers showed high surface activity and the measurements revealed their ability to self aggregate in water at very low concentrations, critical aggregation concentrations (CACs). The CACs were found to decrease with increasing the generation number, which implies that molecular weight and structure play important rules in controlling the surface activity and CAC. The dendritic compounds proved to be effective as adhesion promoters for urea formaldehyde (UF) resins when applied as wood adhesive systems, which was ascribed in partial to the improved wetting over the substrate, a role that is fundamentally related to the huge number of function groups present at the interface. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhancing the properties of urea formaldehyde wood adhesive system using different generations of core‐shell modifiers based on hydroxyl‐terminated dendritic poly(amidoamine)s

Different generations of hydroxy‐terminated dendritic poly(amidoamine) (Gn? OH) with ethylenediamine as a core were prepared by successive alternative addition of methylacrylate and the core up to the third generation while employing ethanolamine only in the last step of every full generation. The different generations prepared were used as modifiers for urea‐formaldehyde (UF) resins. The enhanced durability and stabilizing effect of the (Gn? OH)s along with the reduced levels of free formaldehyde and improved mechanical performance of wood joints glued with the modified resins are discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and antioxidant activities in polyolefin of dendritic antioxidants with hindered phenolic groups and tertiary amine

Two novel primary antioxidants with dendritic structure and hindered phenolic groups were synthesized using 3‐(3,5‐diter‐butyl‐4‐hydroxyphenyl) propionic acid as raw material and dendritic poly(amidoamine) (PAMAM) as linker in chloroform. The antioxidant activities of the dendritic antioxidants were evaluated in polyolefin by melt flow index (MFI), yellowness index (Y.I.), and oxidation induction time (OIT). The dendritic antioxidants had excellent processing property and oxidation resistance behavior in polyolefin. At the same weighed amount of antioxidant, the MFI and Y.I. values of mulitiple‐extruded polyethylene (PE) stabilized with the dendritic antioxidants were smaller than those of the commercial antioxidants, as well as the OIT values of polyethylene (PE) stabilized with the dendritic antioxidants were larger. Applying to polypropylene, the antioxidant ability of the second‐generation dendritic antioxidant (G2.0 dendritic antioxidant) with larger molecular weight was superior to the commercial antioxidants and that of the first‐generation dendritic antioxidant (G1.0 dendritic antioxidant) was equal to the commercial antioxidants. The dendritic antioxidants can prevent polyolefin from breaking of macromolecular chain in processing and had stabilizing effect in polyolefin in service life by donating H‐atoms and electron to free radicals. The dendritic antioxidants combined with Irgafos 168 had improvement of antioxidant activities of the dendritic antioxidants in polyolefin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

树枝状聚醚表面活性剂的合成与性质

以1.0G乙二胺为核的树状大分子聚酰胺-胺为起始剂,氢氧化钾为催化剂,分别与环氧丙烷(PO)、环氧乙烷(EO)反应合成了一系列二嵌段树枝状聚醚表面活性剂(DPE)。采用端基滴定法测定了产品的羟值,并根据理论结构计算出聚醚的相对分子质量;通过吊环法测定聚醚的表面张力,并探讨了化学结构对其性能的影响。结果表明这类具有新型化学结构的聚醚具有良好的表面活性,树枝状聚醚的表面活性随PO比率的提高而增强,而当聚醚的结构(EO/PO)相同时,相对分子质量对其表面活性的影响不大。     

Sustained release properties of arborescent polystyrene-graft-poly(2-vinylpyridine) copolymers

The release kinetics of small molecules from dendritic graft copolymer micelles incorporating an arborescent polystyrene (PS) core and a poly(2-vinylpyridine) (P2VP) shell were investigated in dilute HCl solutions by fluorescence and UV spectroscopies. The redistribution of pyrene and perylene among arborescent micelles was studied by the fluorescence resonance energy transfer (FRET) technique, and was characterized by an initial burst in exchange followed by gradual equilibration of the probes. Fluorescence quenching experiments demonstrated that the diffusion coefficient of pyrene increased for copolymer micelles of higher generations, suggesting a more porous shell structure for the higher generation arborescent PS-g-P2VP copolymers. In vitro release tests for indomethacin and lidocaine monitored by UV spectroscopy showed that sustained release characteristics were achieved, the release rate being higher for lidocaine due to its higher water solubility at low pH. The release rate of indomethacin increased for lower generation micelles and for higher micelle loadings, in agreement with a diffusion-controlled release mechanism. An increasing fraction of the indomethacin molecules loaded in the micelles remained trapped for higher generation copolymers. The diffusion coefficient and the release rate of indomethacin were calculated by fitting the solution of Fick's second law of diffusion to the experimental data. While the initial release rate decreased for higher generations, the trends observed for the diffusion coefficients were similar to those determined for pyrene in the fluorescence quenching experiments. This result is again consistent with a more diffuse shell structure for higher generation micelles, possibly due to the enhanced electrostatic repulsions between the charged P2VP chains.     

Synthesis and incorporation in Langmuir films of oligophenylenevinylene dendrimers bearing a polar head group and different dendritic poly(benzyl ether) branches

Oligophenylenevinylene (OPV) units containing a hydroxyl polar head group and different dendritic poly(benzyl ether) branches bearing aliphatic chains (n-propyl and n-dodecyl) have been synthesized. The obtained dendrimers were characterized by ¹H and ¹³C NMR, FTIR and absorption spectroscopies. Optical properties of the dendrimers have been studied in toluene and dichloromethane solutions. Changes in the maximum absorption wavelength were observed for the dendrimers OPV core. Increasing the dendron branches generation gave rise to a hypsochromic shift of the maximum absorption band of the OPV core. The ability of all dendrimers to form Langmuir films at the air-water interface was also investigated; the obtained films were characterized by surface pressure versus molecular area isotherms, and by compression-expansion cycles (hysteresis curves). All dendrimers were able to form stable Langmuir monolayers in the air-water interface, and exhibited a good reversible behavior upon successive compression/expansion cycles. The terminal alkyl chains length of the dendritic branches has a remarkable influence on the packing of highest generation dendrimers in the monolayers. These dendrimers can be promising prospects for the preparation of Langmuir-Blodgett films, in view of optical and electronic potential applications.     

Catalysis by Mesoporous Dendrimers

The present study reports the divergent synthesis, characterization and catalytic properties of different generation of triazine based aromatic amine dendritic mesoporous silicas derived via a stepwise functionalization of mesoporous silica substrates of different pore sizes with 2,4,6 tricholorotriazine and ethylene diamine. Mesoporous dendritic silicas up to second generation (2G) are grown in side the channels of mesoporous silica materials with 4 and 7 nm pore sizes. The catalytic properties of resulted dendritic materials in Knoevenagel condensation reaction were compared to the aliphatic polyamidoamine dendrimers that are also grown up to second generation (2G) inside the mesoporous channels. The reusability study of both aliphatic and aromatic dendritic mesoporous silica systems is also compared.     

Thermosensitive dendritic stars of tert-butyl-glycidylether and glycidol - Synthesis and encapsulation properties

Dendritic block copolymers of hydrophobic core and hydrophilic shell were prepared by a multi-step process based on anionic ring-opening polymerization. In the first step, amphiphilic stars with four or six poly(tert-butyl-glycidylether)-block-polyglycidol arms were synthesized. The hydroxyl groups of polyglycidol after ionization served as initiation centers for sequential anionic polymerization of tert-butyl-glycidylether and 1-ethoxyethyl-glycidylether. Selective removal of protective groups of glycidol hydroxyls yielded amphiphilic, dendritic copolymers with a hydrophobic core and hydrophilic shell. The hydrophobicity of the dendritic core depended on the composition of the star macroinitiator. The number of reactive hydroxyl groups in the shell was controlled by the number and length of the outer polyglycidol blocks. The structure and molar mass of the copolymers obtained were characterized by GPC-MALLS and NMR spectroscopy.The aqueous solution properties of the copolymers were studied. Some of dendritic copolymers aggregated at elevated temperature. The dependence of phase transition temperature and dimension of aggregates on the copolymer composition were followed by light scattering techniques. The spherical aggregates were visualized by AFM. The encapsulation efficiency of a hydrophobic compound (pyrene) was followed by UV-VIS spectroscopy.     

Crystal structure, melting behaviour and equilibrium melting point of star polyesters with crystallisable poly(ε-caprolactone) arms

Star polymers consisting of poly(ε-caprolactone), PCL, attached to third generation dendrimer, hyperbranched and dendron cores have been studied by differential scanning calorimetry and wide-angle X-ray scattering. The degree of polymerisation of the PCL arms of the star polymers ranged from 14 to 81. The crystal unit cell was the same for the star polymers as for their linear PCL analogues. The star polymers showed a lower degree of crystallinity than the linear PCL, suggesting that the dendritic cores imposed restriction on PCL crystallisation. Slow heating of rapidly cooled samples led to crystal rearrangement—a gradual increase in melting point with decreasing heating rate and recrystallisation followed by additional high temperature melting. The tendency for crystal rearrangement was less pronounced in star polymers based on dendrimer or hyperbranched cores, suggesting that the dendritic cores constitute an obstacle to crystal rearrangement. The star polymers showed higher equilibrium melting points than the linear PCL analogues. It is suggested that covalent attachment of the PCL arms to the dendritic core reduced the positional freedom and the entropy of the melt with respect to that of linear PCL.