An efficient one‐pot access to poly(arylene ethynylene) homopolymers: Use of the Bu3Sn?moiety as a recyclable carrier to introduce the ethynyl unit into the chain

The palladium‐catalyzed Stille coupling of an aromatic diiodide with half an equivalent of tributyl(ethynyl)tin results in a complex mixture containing the diethynylaromatic compound, the iodo(ethynyl)aromatic compound, unreacted diiodide and the tributyltin iodide side product. Addition of LDA to this mixture, while leaving the iodoaromatic moieties unaffected, causes deprotonation of the ethynyl functionalities, which immediately recombine with tributyltin iodide to form a mixture of bis(tributylethynyltin)aromatic, iodo(tributylethynyltin)aromatic, and unchanged diiodide. Being the palladium catalyst still active, it is sufficient to warm up this mixture to obtain the coupling of the tributylethynyltin and iodo moieties resulting in the formation of a poly(arylene ethynylene) polymer. Isolation of the polymer is easily and rapidly achieved by precipitation, while distillation of the mother liquor allows recovery of the tributyltin iodide side product. The latter can be utilized for the preparation of new tributyl(ethynyl)tin, thus allowing a convenient turnover of the tributyltin moiety. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2603–2621, 2000     

沉淀剂对含有氨侧基的聚苯撑乙炔发光性能的影响

通过单体4-[(2,5-二溴苯)乙炔基]苯胺和1,4-二乙炔基-2,5-二戊氧基苯之间的Sonogashira偶合反应合成了带有p-氨基苯乙炔基共轭侧基的聚对苯撑乙炔（(PAnPE）). 该共轭聚合物的THF溶液（(2××10-－5 mol•·L-－1）)在473和519 nm处呈现两个比较强的荧光发射峰. 通过调节在聚合物PAnPE-THF溶液中所加入三种沉淀剂（(甲醇、乙酸、稀盐酸溶液）)的体积比例, 来改变PAnPE分子链的聚集态结构, 进而研究对其发光性能的影响规律. 实验结果表明: 由于沉淀剂与聚合物PAnPE分子链之间相互作用能力与方式的不同, PAnPE两个荧光峰的发射强度因聚合物分子链聚集结构不同而呈现不同的变化规律, 这有助于实现在化学传感器中的应用.     

Water‐soluble meta‐poly(phenylene ethynylene) oligomers with stable helical secondary structure

Two novel water‐soluble meta‐poly(phenylene ethynylene) (mPPE) copolymers were synthesized and characterized, each contained ester and amine functional groups attached to exohelix positions on the phenylene rings and one contained methoxy endohelix functional groups. Secondary structure formation was investigated for these materials in aqueous solutions using ultraviolet and fluorescence spectroscopy. Additionally, the folding behaviors are reported for the mPPEs and their protected amine precursors in other protic and aprotic solvents. Results indicate that both mPPEs are able to form stable helical structures in water, while only the nonmethoxylated polymer exhibited a helical structure in acetonitrile and several alcohols. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Allylic monomers as reactive plasticizers of polyphenylene oxide. Part III – Rheological and mechanical properties

The chemorheology of blends of diallyl ortho-phthalate (DAOP) as reactive plasticizer of polyphenylene oxide (PPO) were monitored during their cure with either dicumyl peroxide (DCP) or tert-butyl hydroperoxide (TBHP), and their mechanical properties and morphology were studied. The steady shear and dynamic rheology behaviour was consistent with chemical gelation of DAOP in blends with low concentrations of PPO but the gelation behaviour at higher PPO concentrations was more complex. Dynamic mechanical thermal analysis of the blends of PPO:DAOP cured with either DCP or TBHP indicated a two phase structure. For PPO:DAOP/DCP, the lowest transition (between 150 °C and 200 °C) was attributed to a DAOP-rich phase and its T_g was higher than that for pure DAOP/DCP due to the presence of PPO in the DAOP-rich phase. The smaller damping shoulder near 250 °C was caused by a PPO-rich phase with a T_g that was lower than pristine PPO due to the presence of unpolymerized or polymerized DAOP. In contrast, the glass transition region of the PPO:DAOP/TBHP system was very broad due to an overlap of the transitions for DAOP-rich and PPO-rich phases caused by higher levels of unpolymerized DAOP. SEM observations of the blends revealed a two phase morphology with PPO-rich particles in a poly-DAOP matrix for blends with ?30 wt% PPO, a co-continuous morphology for blends with 40 wt% PPO, and a phase inverted morphology with more than 50 wt% PPO. These SEM observations agree with studies of the swelling, disintegration or dissolution of matrix of the blends in solvent.     

Branched polyphenylenes and phenylene dendrimers: NMR and optical studies

Two branched polyphenylenes with 1,3,5-triphenylbenzene as branching centers were synthesized together with a family of phenylene cyclotrimers as model compounds. On the basis of the NMR analysis, specifically ¹H NMR, ¹³C NMR and 2D heteronuclear correlation experiments (HSQC and HMBC) of model compounds, the huge number of overlapping signals in the polymer spectra are attributed to aromatic protons and carbon atoms of the branched phenylene structure. The comparison with absorption spectra of linear model compounds clearly shows that the polymer optical properties depend on the length of the segments between the branching cores. This result strongly supports the proposed NMR assignment proving that the combination of the two techniques is a powerful tool for unveiling complex branched structures.     

纳米花状MnO_2/PPS功能复合滤料的制备及其NH_3-SCR脱硝性能研究

首先采用表面活性剂十二烷基硫酸钠(SDS)对聚苯硫醚(PPS)滤料进行表面活化,由于SDS亲水基团(SO_4~–)与溶液中的H~+发生静电吸附作用,使得之后高锰酸钾在PPS滤料表面原位生成纳米花状二氧化锰,制得nf-MnO_2/PPS复合滤料;并通过探讨高锰酸钾与滤料的质量比、反应时间对nf-MnO_2/PPS复合滤料结构及性能的影响,从而得到最佳制备条件.并利用场发扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X-射线光电子能谱(XPS)、脱硝活性测试等分析手段对该复合滤料的结构和性能进行了研究;在其基础上利用原位聚合法,在复合滤料表面形成聚吡咯包覆层,制得nf-MnO_2/PPy@PPS复合滤料,并通过多种测试分析手段对改性滤料的结构和性能进行了研究.最后,脱硝测试结果显示,由最佳条件制备出的nf-MnO_2/PPS表现出了最优异的脱硝活性,其在80~180℃时的NO转化率达到36%~100%,nf-MnO_2/PPy@PPS表现出了更好的结合强度和催化稳定性能,但脱硝活性有所下降.     

Structure—Property relationships for exciton transfer in conjugated polymers

The ability of conjugated polymers to function as electronic materials is dependent on the efficient transport of excitons along the polymer chain. Generally, the photophysics of the chromophore monomer dictate the excited state behavior of the corresponding conjugated polymers. Different molecular structures are examined to study the role of excited state lifetimes and molecular conformations on energy transfer. The incorporation of rigid, three‐dimensional scaffolds, such as iptycenes and cyclophanes, can encourage an oblique packing of the chromophore units of a conjugated polymer, thus allowing the formation of electronically‐coupled aggregates that retain high quantum yields of emission. Rigid iptycene scaffolds also act as excellent structural directors that encourage complete solvation of PPEs in a liquid crystal (LC) solvent. LC‐PPE mixtures display both an enhanced conformational alignment of polymer chains and extended effective conjugation lengths relative to isotropic solutions, which leads to enhanced energy transfer. Facile exciton migration in poly(p‐phenylene ethynylene)s (PPEs) allows energy absorbed over large areas to be funneled into traps created by the binding of analytes, resulting in signal amplification in sensory devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

含二茂铁齐聚苯乙炔分子导线的合成

通过二碘代二茂铁与不同炔化物进行Sonogashira偶联反应,合成了3种新颖的含有二茂铁单元的苯乙炔齐聚物,用1H NMR、13C NMR和MS测试技术分别对其结构进行了表征。 并借助量子化学计算对3种分子的电子结构进行了预测,结果显示,该类型分子导线具有不同于其它类型苯乙炔齐聚物的LUMO能级持续衰减特征,因此极有可能具备极为优良的电子传输性能。     

Cross polarization effect of donor–acceptor group on a potential single‐molecule transistor

Theoretical investigation of the polarization effect on a potential single‐molecule transistor has been studied with density functional theory. 4,4′‐(2‐Amino‐5‐nitro‐1,4‐phenylene)bis(ethyne‐2,1‐diyl) dibenzenethiol (AN‐OPE), containing a donor and an acceptor (D–A) crossed to its oligo(p‐phenylene‐ethynylene) (OPE) backbone, was used as a prototype for this study. Simulation results indicate that AN‐OPE has a higher on/off ratio on conductance than OPE because of the larger polarization along the D–A direction. This high on/off ratio was proved by the 20 times variation in molecular charge, 15 times variation in bond lengths, 49 times variation in polarizability, 9 times variation in the rotation angles, and 13 times variation in the highest occupied molecular orbital–lowest unoccupied molecular orbital gaps under the same gate using B3LYP/6‐31G (d, p). And results imply that conjugated molecules with a cross D–A structure could be a good direction for constructing a better single‐molecule field‐effect transistor. Copyright © 2014 John Wiley & Sons, Ltd.     

Segmented conjugated polymers

Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying excitation energies. The latter feature, especially when the chromophores are fluorescent, like in MEHPPV, makes these systems particularly interesting from the photophysics point of view. Segmented MEHPPV-x samples, wherex represents the mole fraction of conjugated segments, were prepared by a novel approach that utilizes a suitable precursor wherein selective elimination of one of the two eliminatable groups is affected; the uneliminated units serve as conjugation truncations. Control of the compositionx of the precursor therefore permits one to prepare segmented MEHPPV-x samples with varying levels of conjugation (elimination). Using fluorescence spectroscopy, we have seen that even in single isolated polymer chains, energy migration from the shorter (higher energy) chromophores to longer (lower energy) ones occurs — the extent of which depends on the level of conjugation. Further, by varying the solvent composition, it is seen that the extent of energy transfer and the formation of poorly emissive inter-chromophore excitons are greatly enhanced with increasing amounts of non-solvent. A typical S-shaped curve represents the variation of emission yields as a function of composition suggestive of a cooperative collapse of the polymer coil, reminiscent of conformational transitions seen in biological macromolecules.