末端含三甲基硅基树枝状低聚苯的合成与表征

树枝状聚合物是一类结构有序、有特定分子量、末端可带活性官能团的多功能聚合物,其应用研究涉及信息贮存材料、高级催化剂、非线性光学材料、液晶材料、纳米材料、缓释药物载体、传感器材料、污水处理剂、分离膜及流变学改性剂等领域.以含多功能团的低聚苯为中心核,通过过渡金属催化的芳基偶联反应或Diels-Alder环加成反应,经“收敛法”或“发散法”可以制得结构准确、尺寸可控的树枝状聚苯纳米材料;另一方面,由于核心分子结构的多样性,可以设计、合成拓扑形态各异的树枝状聚苯应用于有机发光材料、有机磁性体、碟状液晶、管束状分子通道、分子识别、储氢材料及锂电池等领域,从而丰富其结构与性能关系的研究内容.因此,树枝状聚苯中心核的设计与合成在这类材料的应用研究中显得尤为重要.本工作设计与合成了一类树枝状聚苯的中心核12和13,其分子末端的生长点被三甲基硅基（TMS-）所保护;采用凝胶渗透色谱（GPC）和粉末X射线衍射等分析手段,以及与其母体结构,即末端不含三甲基硅基的模型化合物1,3,5-三（3＇,5＇-二苯基苯基）苯11进行比较,探讨了分子末端的三甲基硅基及其取代位置对树枝状低聚苯的凝胶渗透色谱行为和结晶性的影响.     

SYNTHESIS AND CHARACTERIZATION OF SOLUBLE POLYPHENYLENE COMPOSED OF p-PHENYLENE AND m-PHENYLENE UNITS

NiCl_2(bpy) catalyzed polycondensation between p-dibromobenzene and m-dibromobenzene has been carried outunder vdrious conditions. The polycondensation endows the copolymer with an M_n of 2300 (by GPC, polystyrene standards)and good solubility in organic solvents. The fluorescence spectra of the copolymer measured with tetrahydrofuran solutionshows an emission maximum (λ_(max)) at 372.8 nm, whereas for the film the maximum shifts to 436.6 nm.     

Heterogenized polymetallic catalysts: Part III. Catalytic air oxidation of alcohols by Pd(II) complexed to a polyphenylene polymer containing β-di- and tri-ketone surface ligands

This paper describes further studies on mono- and bi-metallic catalysts attached to a polymer support by β-di- and tri-ketone surface ligands. The previous two papers described the oxidation of catechol by the heterogeneous catalysts using Cu(II), Fe(III) and Pd(II) as the metal species. The present study expands these studies to a series of mono- and polyfunctional alcohols using Pd(II) as the metal species. The final catalytic surfaces were prepared by treatment of the modified polymer with a very reactive form of Pd(II), [Pd(CH₃CN)₄]²⁺. The simple alcohols gave increases in rates of up to 5-fold for the bimetallic systems. As might be expected glycols and - -glucose gave even higher increases in rate in going from the mono- to the bi-metallic catalyst. For ethylene glycol the factor was 30. Unsaturated alcohols gave the most dramatic results. With the monometallic catalyst, the products from allyl alcohol consisted of 25% acrolein resulting from direct alcohol oxidation and 75% 3-hydroxypropanal resulting from Wacker-type oxidation of the double bond. With the bimetallic catalyst the overall rate increased by a factor of 10 and the products consisted of 80% acrolein and 20% 3-hydroxypropanal. The actual rate increase for the direct alcohol oxidation is calculated to be a factor of 32. 4-Penten-2-ol and 4-penten-1-ol gave rates that were lower than the monofunctional alcohols. This is attributed to inhibition by olefin π-complex formation with the Pd(II).     

RHEOLOGICAL BEHAVIOR OF POLYPHENYLENE SULFIDE/POLYAMIDE-66 BLENDS

Blends of polyphenylene sulfide (PPS) containing trace amounts of branching and/orcross-linking in chain and Polyamide-66(PA-66) have been prepared by melt blending. Therheological behavior of PPS/PA-66 blends has been studied by means of capillary rheo-meter, and compared with PPS. The effects of shear rate, shear stress and temperature onthe flow of PPS/PA-66 blends and PPS are discussed. The non-Newtonian indexes andthe activation energies of viscous flow are obtained. The results show that the apparentviscosity of PPS/PA-66 blends is not sensitive to shear rate and stress, but decreases withthe elevation of temperature. On the contrary, the apparent viscosity of the PPS decreasesobviously with the increasing of shear rate and shear stress, but it is increased by theelevation of temperatue.     

Hydration effect on the electronic transport properties of oligomeric phenylene ethynylene molecular junctions

A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H₂O molecules accumulated in the vicinity as recently reported by Na {\it et al.} [\wx{Nanotechnology}{18} 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H₂O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H₂O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H₂O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.     

侧链含氨基的聚(对亚苯基亚乙炔基-对亚苯基-咔唑)三元共聚物的合成及其聚集态下荧光特性

通过Sonogashira偶联反应制备了含有4-[2-(对苯胺)乙烯基]苯(M1)、2,5-二戊烷氧基-1,4-二乙炔基苯(M2)和9-辛基咔唑(M3)3种结构单元的三元共轭聚合物PPEC,并通过核磁共振氢谱确定了3种结构单元的比例为0.54∶1.00∶0.46(M1∶M2∶M3).由于在PPEC的侧链中含有氨基基团,通过在PPEC的THF溶液中分别加入水、甲醇和正己烷,诱导其产生聚集,其聚集后的荧光性质表现出明显的不同,在THF与水的混合溶剂中,PPEC发光强度会随着水含量的增加先是急剧降低,而后在高水含量时发光强度又显著增强;在THF与甲醇的混合溶剂中,PPEC发光强度随着甲醇的加入只是逐渐降低;在THF与正己烷的混合溶剂中,PPEC的发光强度则会随着正己烷的增加而增强.该结果表明氨基通过与水,或者自身所形成氢键作用,改变了PPEC分子链之间的聚集态结构,降低了分子内旋转非辐射能量效率,从而有效改善共轭聚合物的主链发光性质,这为设计聚集态下(或固态下)高性能的荧光共轭聚合物提供了一种新思路.     

Controlling the Structural and Electrical Properties of Diacid Oligo(Phenylene Ethynylene) Langmuir–Blodgett Films

The preparation, characterization and electrical properties of Langmuir–Blodgett (LB) films composed of a symmetrically substituted oligomeric phenylene ethynylene derivative, namely, 4,4′‐[1,4‐phenylenebis(ethyne‐2,1‐diyl)]dibenzoic acid (OPE2A), are described. Analysis of the surface pressure versus area per molecule isotherms and Brewster angle microscopy reveal that good‐quality Langmuir (L) films can be formed both on pure water and a basic subphase. Monolayer L films were transferred onto solid substrates with a transfer ratio of unity to obtain LB films. Both L and LB films prepared on or from a pure water subphase show a red shift in the UV/Vis spectrum of about 14 nm, in contrast to L and LB films prepared from a basic subphase, which show a hypsochromic shift of 15 nm. This result, together with X‐ray photoelectron spectroscopic and quartz crystal microbalance experiments, conclusively demonstrate formation of one‐layer LB films in which OPE2A molecules are chemisorbed onto gold substrates and consequently ? COO? Au junctions are formed. In LB films prepared on a basic subphase the other terminal acid group is also deprotonated and associates with an Na⁺ counterion. In contrast, LB films prepared from a pure water subphase preserve the protonated acid group, and lateral H‐bonds with neighbouring molecules give rise to a supramolecular structure. STM‐based conductance studies revealed that films prepared from a basic subphase are more conductive than the analogous films prepared from pure water, and the electrical conductance of the deprotonated films also coincides more closely with single‐molecule conductance measurements. This result was interpreted not only in terms of better electron transmission in ? COO? Au molecular junctions, but also in terms of the presence of lateral H‐bonds in the films formed from pure water, which lead to reduced conductance of the molecular junctions.     

Hydrocarbon links in an octet truss

We use the octet truss of R. Buckminster Fuller to develop a geometric placement method for synthesizing braid representations of knots and links of oligo (phenylene ethynylene)s using the 60° ortho, 120° meta or 180° para phenyl ring substitution angles and respecting the van der Waals repulsion constraints. We show that any knot or link can be realized by a phenylene ethynylene oligomer modeled on the octet truss. Use of this lattice is motivated by the structural constraints of these phenylene ethynylene units. Where in bio-organic chemistry, questions often involve identifying existing knots, for example in DNA strands, organic synthesis is concerned with assembling molecular structures that can be verified to exist in a desired knot topology. This physical realization of a knot as a construction of common organic molecular subunits then facilitates further study of the properties of knotted molecules in general.     

侧基横挂偶极单元的液晶聚苯撑乙炔的合成与表征

为了制备电致偏振光发光材料, 以对苯二乙炔和2,5-二溴苯衍生物为单体,通过Sonogashira偶联反应, 采用不同Pd催化剂, 合成了一种侧基横挂偶极基团的液晶聚苯撑乙炔. 单体的化学结构通过IR, NMR和元素分析等方法得到确证. 聚合物外观为黄色粉状固体, 室温下溶于CHCl3和THF等有机溶剂. 将聚合物加热到各自的玻璃化转变温度以上都能形成液晶态并显示双向液晶性. 考察了不同催化剂对合成的聚合物的分子量、聚合物链中单体单元的结构排列以及液晶性质的影响. 结果表明, 两种不同的Pd催化剂对合成的聚合物的分子量以及液晶态温度范围影响不大, 但对聚合物的立构规整性以及聚合物的液晶态织构有较大的影响. Pd(PPh3)4作催化剂合成的聚合物中单体单元的结构排列较单一, 可以观察到清晰的液晶态织构. 以PdCl2(PPh3)2为催化剂合成的聚合物链中单体单元的结构排列相对复杂, 液晶态织构不明显. 变温X 射线衍射研究证实聚合物均为向列相液晶.     

一类基于苝酰亚胺和亚苯基亚乙炔基交替共轭聚合物的合成与表征

以1,7"bay"位置溴化苝酰亚胺为电子受体、低聚亚苯基亚乙炔基(OPE)为电子给体,通过Sonagashira反应制备了一系列不同OPE含量的具有p-n结构主链全共轭交替聚合物,并对其光物理和电化学性质进行了表征.紫外-可见吸收光谱表明,聚合物具有较宽的光吸收范围(350~900 nm),有利于提高体系的光吸收效率;荧光光谱实验发现,对苝酰亚胺单元进行选择性激发,产生由分子内电荷分离所导致的荧光猝灭现象,为该材料应用于光伏器件提供了理论和实验依据.