低介电常数聚喹啉衍生物薄膜的合成与表征

采用等离子体聚合技术合成了一种新型的低介电常数聚喹啉衍生物薄膜: 聚3-氰基喹啉(PP3QCN)薄膜. 借助于傅里叶变换红外光谱(FT-IR)、紫外-可见(UV-Vis)吸收光谱、X光电子能谱(XPS)和原子力显微镜(AFM)对薄膜结构进行了系统表征. 结果表明, 等离子体聚合条件对沉积膜的化学结构、表面组成、膜形态以及介电性能均有影响. 在较低的等离子体放电功率(10 W)条件下, 可得到具有较高芳环保留率和较大π-共轭体系的高质量聚3-氰基喹啉薄膜材料; 而在较高功率(25 W)条件下, 聚合过程中会出现比较严重的单体分子破碎, 形成较多非π-共轭体系的聚合物, 从而导致聚3-氰基喹啉的共轭度降低. 聚3-氰基喹啉薄膜的介电性能测试结果表明, 低放电功率(10 W)条件下制得的聚3-氰基喹啉薄膜具有比较低的介电常数值, 仅为2.45.     

主链含有非共轭结构的聚芴类蓝光聚合物的合成与性能研究

通过Suzuki偶合反应合成出了主链中含有非共轭烷氧基组分(-O-CH2-CH2-CH2-CH2-O-)的聚芴类衍生物聚- 2,7-(9,9-二辛基芴)-co-4,4’-丁氧基二苯(PFP)和聚-2,7-(9,9-二辛基芴)-co-4,4’-丁氧基二苯-co-N-苯基-4,4’-二苯胺(PFTP11)并通过相同的条件合成出主链由芴和三苯胺交替相连的聚合物聚-2,7-(9,9-二辛基芴)-co-N-苯基-4,4’-二苯胺(PFTPA)作为参比材料. 通过1H NMR和FT-IR分析对这些聚合物的化学结构进行了表征. 这三种聚合物在常用的有机溶剂中具有很好的溶解性, 可通过溶液加工的方式制备聚合物薄膜. 这些聚合物均具有较高的热分解温度(＞400 ℃), 聚合物PFP具有较高的玻璃化转变温度(～130 ℃)而PFTP11和PFTPA则未出现明显的玻璃化转变过程. 通过对聚合物的吸收特性进行测试得知它们具有较大的光学带宽(2.89～3.29 eV). 所有聚合物在固体薄膜状态下均发射出蓝色荧光, PFP, PFTP11和PFTPA的最大PL发射分别位于425, 437和440 nm. 通过对其电化学性能进行测试可知由于三苯胺基团的引入聚合物的HOMO能级明显提高, 这意味着聚合物的空穴传输能力得到了有效的改善.     

全氟并五苯在半金属Ga表面的分子二聚化及自组装单层

利用超高真空扫描隧道显微镜(UHV-STM)和有机分子束沉积(OMBD)方法研究了全氟并五苯(perfluoropentancene,PFP)分子在半金属Ga表面的吸附和两维自组装. 在低覆盖度下单个PFP分子在Ga表面上表现出很高的迁移性. 在1分子单层(monolayer, ML)时PFP分子发生二聚化并在 Ga 表面上无序排列. 轻度热退火可导致PFP两维自组装: 二聚体排列为高度有序的一维分子带阵列, 带中 PFP二聚体排列为砖墙(brick wall)结构. 在高分辨 STM图中, PFP分子两端出现亮暗相反的圆形突起, 并且相邻分子的亮暗极性相反, 表明PFP分子带有电偶极矩, PFP二聚体带有电四极矩. 因此, PFP分子二聚体的形成机制可唯像解释为反向电偶极矩之间的静电吸引作用; 二聚体的砖墙排列结构可归结为同向电四极矩之间的静电排斥作用.     

基于共轭高分子复合物能量转移的非标记DNA检测

非标记DNA检测是一种高灵敏度、高选择性的DNA检测方法, 具有重要的科学和社会意义. 本文采用交叉偶联法制备了水溶性阳离子共轭聚合物: 聚(9,9-双(6'-N,N,N-三甲胺盐-己烷基)-芴亚苯基)(PFP); 利用氧化加成聚合反应制备了水溶性阴离子共轭聚合物: 聚(3-噻吩乙酸钠)(P3TSA). 通过核磁共振氢谱(¹H NMR)、傅立叶变换红外光谱(FTIR)等对其结构进行了表征. PFP与P3TSA通过静电相互作用形成稳定的高分子复合物. 利用紫外-可见光谱(UV-vis)和荧光发射光谱证明共轭高分子复合物能够发生能量转移. 保持PFP的浓度不变, 高分子复合物能量转移效率(ETEF)随着P3TSA浓度的增加而逐渐增大. 选取ETEF较高的样品, 考察了DNA探针用量对高分子复合物ETEF的影响. 随着DNA探针浓度的增加, ETEF逐渐减弱. 最后, 利用0.2 nmol DNA探针进行了DNA杂交配对检测. 实验结果表明, 这种检测方法可以明显区分完全互补配对、双碱基错配和非完全互补配对的目标DNA. 简而言之, 我们成功发展了一种基于共轭高分子复合物能量转移、具有高选择性的非标记DNA检测方法.     

末端含蓝光发色团的超支化聚苯材料的合成

在聚合物发光材料研究领域中,作为三元色之一的蓝色发光材料的设计与合成倍受关注．一维线型结构的聚对苯及聚烷基芴等是典型的蓝色发光材料;线型结构的聚对亚苯亚乙烯基(PPV)及聚对亚苯亚乙炔基(PPE)具有电子流动性好,在溶液中有高荧光量子效率也可衍生得到蓝色发光材料,这主要是在共轭聚合物主链上嵌入非共轭部分,     

聚对苯乙炔-噻吩共轭聚合物电致发光性能的研究

1990年剑桥大学的Ｂｕｒｒｏｎｇｈｅｓ[1] 等首次提出用共轭高分子聚 (苯乙撑 ) (ＰＰＶ)为发光层材料制备了聚合物电致发光器件 ,不久Ｈｅｅｇｅｒ[2 ] 等证实了这个结果 ,随后发光聚合物的研究在世界范围内广泛开展起来 ,ＰＰＶ目前已被证实是一个潜在的电致发光材料[3 ] .共轭聚合物用于电致发光有以下特点 :( 1 )可通过旋涂、浇铸等方法制成大面积薄膜 ;( 2 )共轭聚合物大多有优良的稳定性 ;( 3)共轭聚合物电子结构 ,发光颜色能够通过化学结构的改变和修饰进行调节 ;( 4 )聚合物做发光层时可制成非常薄的膜 ( 1 0～ 1 0 0ｎｍ) ,可消除…     

从导电聚吡咯到共轭聚合物光伏材料——我在中科院化学所30年共轭高分子研究历程

本文简要回顾了本人在中科院化学所30年的研究历程,重点介绍了在共轭高分子(包括导电聚吡咯电化学、聚合物发光电化学池(LEC)和共轭聚合物给体光伏材料)方面的研究成果。在导电聚吡咯电化学方面,对导电聚吡咯的电化学制备和电化学性质进行了深入研究,阐明了各种电化学聚合条件对制备的导电聚吡咯电导和力学强度等的影响,发现电解液溶剂给电子性(Donor number)对吡咯电化学聚合制备的导电聚吡咯电导的影响:溶剂Donor number越小制备的导电聚吡咯电导越高;使用非离子表面活性剂添加剂在水溶液中制备出表面非常光滑和高力学强度的导电聚吡咯薄膜;对于吡咯电化学聚合提出了电解液阴离子参与的阳离子自由基聚合机理,并推到出吡咯电化学聚合反应的动力学方程;发现在NaNO3水溶液中电化学聚合制备的导电聚吡咯除存在主链氧化、对阴离子掺杂结构外,还存在质子酸掺杂结构;阐明了导电聚吡咯在水溶液中电化学还原和再氧化的机理及其电化学过程的可逆性和稳定性,以及导电聚吡咯在有机电解液中特殊的第一次还原和再氧化的机理。在LEC方面,通过交流阻抗法确认了LEC的电化学掺杂机理和p-i-n结构,合成了多种适用于LEC的主链带离子导电单元的兼具离子导电性的发光嵌段共聚物,避免了LEC活性层中存在的发光聚合物和离子导电聚合物的分相问题;使用离子液体作为电解质制备了室温准冷冻p-i-n结LEC,改善了LEC的电致发光性能。在共轭聚合物给体光伏材料方面,我们提出了通过共轭侧链来拓宽聚合物吸收和提高空穴迁移率的分子设计思想,设计和合成了一系列带共轭侧链的二维共轭聚噻吩衍生物以及基于二噻吩取代苯并二噻吩的窄带隙高效二维共轭聚合物给体光伏材料。我们使用烷硫基取代进一步降低了这类二维共轭聚合物的HOMO能级从而进一步提高了其光伏性能。最后介绍了本组二维共轭聚合物给体光伏材料在非富勒烯聚合物太阳能电池方面的最新研究进展。     

染料敏化太阳能电池中额外给体引入对经典D-π-A型敏化剂性能影响的理论研究

为了探讨D-D-π-A型染料中双给体对敏化剂性能的影响, 本文结合密度泛函理论(DFT)及含时密度泛函理论(TD-DFT)对染料1~4的几何结构、 电子结构、 吸收光谱、 电化学性质、 电子复合程度以及半导体导带边缘的移动等进行了对比研究. 结果表明, 相比于经典的D-π-A型染料分子1, 在分子2~4(D-D-π-A型双给体染料) 中额外引入给体, 尽管对导带能级移动的改变不是很显著, 但是可以改变体系的共轭程度, 增加染料的光吸收强度. 重要的是, 额外给体的引入可以显著增加染料阳离子空穴-半导体之间的距离, 从而减缓注入电子与染料阳离子的复合; 在额外给体中引入杂原子可以使I₂聚集在染料外侧, 从而降低电解质在半导体表面的局域浓度, 进而减缓注入电子与电解质之间的复合速率. 因此, 通过在经典的D-π-A型染料上引入额外的电子给体构筑D-D-π-A型染料可以有效调节染料的光吸收、 电化学及电子复合等方面的性质, 是设计合成高性能染料的可行策略.     

共轭聚合物材料及电致发光器件

共轭聚合物是一种极有应用前景的有机半导体材料,本文综述其研究进展,包括典型共轭聚合物材料PPV、PT、PF等及PPP的工作原理,发展前景和存在的问题。     

全共轭聚噻吩类和聚硒吩类嵌段共聚物的凝聚态结构调控

嵌段共聚物可发生微相分离形成丰富的介观尺度上的相结构,而共轭聚合物是一类具有特殊的力学、导电性能或光电功能的半刚性链高分子.全共轭嵌段共聚物因其兼具两者的特性而备受瞩目.本文着重介绍了近年来课题组在基于全共轭聚(3-烷基噻吩)和聚(3-烷基硒吩)嵌段共聚物体系的研究进展,通过改变体系的分子结构包括主侧链结构、侧链的烷基长度及取代基团等以及对体系在溶液状态及薄膜状态进行后处理包括改变溶剂、热处理、溶剂蒸气处理等来调控体系的微相分离行为和结晶行为,实现对材料凝聚态结构的调控.在此基础上,以有机场效应晶体管和聚合物太阳能电池器件作为最终体现聚噻吩或聚硒吩类体系凝聚态结构与性能关系的平台,将获得的调控体系凝聚态结构的有效策略用于实现其半导体材料物理性能的提升.     

Electrically conductive composites of polyethylene filled with polyamide particles coated with silver

New types of electrically conductive polymeric composites were prepared on a base of high-density polyethylene (HDPE) matrix filled with silver-coated polyamide (PA) particles. The electrical, mechanical and adhesive properties of those composites are reported in this paper. The percolation concentration of the filler within a matrix was found to be 4 vol.%. Composites filled with high filler content were highly electrically conductive; their electrical conductivity reached the value of 6.8 × 10² S cm⁻¹. Mechanical properties and rheology of these composites were discussed. The adhesive properties of the composites to metal sharply increased with an increase in the filler content.     

Molecular fluorescence analysis of rainwater: Effects of sample preservation

Very different filtration and preservation procedures may be found in the literature on the study of the rainwater dissolved organic fraction. Thus, the influence of sample filtration and preservation procedures on the fluorescence of rainwater dissolved organic matter (DOM) was studied in this work. Rainwater was filtered through different filters (quartz 0.22 μm or PVDF 0.45 μm) and excitation (λ_em = 415 nm) and synchronous (Δλ = 70 nm) fluorescence spectra were obtained at the same day of collection, or after preservation by refrigeration (1-7 days) or by freezing (1-4 weeks). The excitation-emission matrix (EEM) spectra of rainwater showed six types of fluorescent bands: two corresponding to humic-like bands, and four resembling proteins. Then, the excitation and synchronous spectra were chosen in order to monitor changes in the humic-like and protein-like bands, respectively. The filtration procedures adopted in this work did not affect the fluorescence properties of the rainwater samples. However, these properties were differently preserved by refrigeration or freezing: after refrigeration, filtered rainwater maintained the original fluorescent properties for at least 4 days, while after freezing fluorescent properties were not always preserved since it occurred a decrease of protein-like fluorescence intensity.     

Effect of impurity on electronic properties of carbon nanotubes

We have studied the effect of impurity on electronic properties of single-walled carbon nanotubes using Density Functional Theory. Electronic band structures and density of states of (4, 4) and (7, 0) carbon nanotubes in the presence of different amount of B and N impurities were calculated. It was found that these impurities have significant effect on the conductivity of carbon nanotubes. The metallic (4, 4) nanotube remains to be metallic after doping with B and N. The electronic properties of small gap semiconducting (7, 0) tube can extensively change in the presence of impurity. Our results indicate that B-doped and N-doped (7, 0) carbon nanotubes can be p-type and n-type semiconductors, respectively.     

Critical influence of the alkane length in surface and liquid-crystalline properties of perfluorodecyl-n-alkanes

Differential scanning calorimetry (DSC) measurements together with texture observation with polarizing microscope revealed the presence of a smectic phase for shorter homologues. Film forming properties of all the perfluorodecyl-n-alkanes synthesized here at the air-water interface were thoroughly investigated. Nearly all the compounds investigated were found to be capable of Langmuir monolayer formation when spread at the water-air interface, apart from semifluorinated alkanes (SFA) containing short hydrogenated moiety (n < 10), which partially dissolve in the water subphase. The investigated homologous series of SFA can be divided into four groups, regarding their liquid-crystalline and surface properties. The first group includes molecules with n = 6-10, which form smectic phases in the bulk and do not form stable monolayers at the free water surface. SFA containing 11 or 12 hydrogenated carbons belong to the second group, forming smectic phases at elevated temperatures, which transform into 3D ordering upon cooling. These molecules are found to form Langmuir monolayers of intermediate stability. The remaining groups contain perfluorodecylalkanes with n > 12, which differ in their calorimetric properties; however, both form very stable films on the water surface and do not exhibit liquid-crystalline properties.     

Profiling food volatiles by comprehensive two-dimensional ga schromatography coupled with mass spectrometry: Advanced fingerprinting approaches for comparative analysis of the volatile fraction of roasted hazelnuts (Corylus avellana L.) from different origins

This study examined how advanced fingerprinting methods (i.e., non-targeted methods) provide reliable and specific information about groups of samples based on their component distribution on the GC × GC chromatographic plane. The volatile fractions of roasted hazelnuts (Corylus avellana L.) from nine different geographical origins, comparably roasted for desirable flavor and texture, were sampled by headspace-solid phase micro extraction (HS-SPME) and then analyzed by GC × GC-qMS. The resulting patterns were processed by: (a) “chromatographic fingerprinting”, i.e., a pattern recognition procedure based on retention-time criteria, where peaks correspondences were established through a comprehensive peak pattern covering the chromatographic plane; and (b) “comprehensive template matching” with reliable peak matching, where peak correspondences were constrained by retention time and MS fragmentation pattern similarity criteria. Fingerprinting results showed how the discrimination potential of GC × GC can be increased by including in sample comparisons and correlations all the detected components and, in addition, provide reliable results in a comparative analysis by locating compounds with a significant role. Results were completed by a chemical speciation of volatiles and sample profiling was extended to known markers whose distribution can be correlated to sensory properties, geographical origin, or the effect of thermal treatment on different classes of compounds. The comprehensive approach for data interpretation here proposed may be useful to assess product specificity and quality, through measurable parameters strictly and consistently correlated to sensory properties and origin.     

Non-fluorinated proton-exchange membranes based on melt extruded SEBS/HDPE blends

This paper reports on functional polymer blends prepared by melt-processing technologies for proton-exchange membrane applications. Styrene–ethylene/butylene–styrene (SEBS) and high-density polyethylene (HDPE) were melt blended using twin-screw compounding, extruded into thin films by extrusion–calendering. The films were then grafted with sulfonic acid moieties to obtain ionic conductivity leading to proton-exchange membranes. The effect of blend composition and sulfonation time was investigated. The samples were characterized in terms of morphology, microstructure, thermo-mechanical properties and in terms of their conductivity, ion exchange capacity (IEC) and water uptake in an effort to relate the blend microstructure to the membrane properties. The HDPE was found to be present in the form of elongated structures which created an anisotropic structure especially at lower concentrations. The HDPE increased the membrane mechanical properties and restricted swelling, water uptake and methanol crossover. Room temperature through-plane conductivities of the investigated membranes were up to 4.5E−02 S cm⁻¹ at 100% relative humidity, with an ionic exchange capacity of 1.63 meq g⁻¹.     

Steric and electronic properties in bicyclic phosphines. Crystal and molecular structures of Se = Phoban-Q (Q = C2, C3Ph, Cy and Ph)

Reacting a series of the bicylic Phoban-Q (9-Q-9-phosphabicyclo[3.3.1]nonane and 9-Q-9-phosphabicyclo[4.2.1]nonane) derivatives (Q = alkyl, cyclo alkyl, aryl) with KSeCN results in the formation of the corresponding phosphine selenides. The first order phosphorus-selenium coupling constants, ¹J_P-Se, ranges from 682 to 689 Hz for the [3.3.1] isomers and from 703 to 717 Hz for the [4.2.1] isomers indicating the former to be significantly more electron rich. The crystal structures of Se = Phoban[3.3.1]-Q (Q = CH₂CH₃, C₃H₆Ph, Cy, and Ph) and Se = Phoban[4.2.1]-Q (Q = Cy and Ph) are reported and reveal PSe bond distances ranging from 2.1090(9) to 2.1245(7) Å. For Q = Cy and Ph the two isomers ([3.3.1] and [4.2.1]) co-crystallise in the same crystal enabling the determination of the molecular structures for both from the same data collection. The cone angles for all ligand derivatives were determined according to the Tolman model but by using the actual P-Se bond distances and were found to be virtually identical ranging from 165° to 175°. Changes in the Q substituent have a minor effect on the overall steric and electronic properties of the Phoban family of ligands and can be used to manipulate physical properties without changing the chemical properties significantly.     

Degradation of pre-aged polymers exposed to simulated recycling: Properties and thermal stability

Accelerated thermal and photo-aging of four homopolymers, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and high-impact polystyrene (HIPS), was performed and the impact of subsequent reprocessing conditions on their properties studied. Polymer samples oven-aged at 100 °C for varying periods of time or UV irradiated in a Weather-o-meter (WOM) at λ = 340 nm were reprocessed in a Brabender plasticorder at 190 °C/60 rpm for 10 min. Chemical changes and the evolution of rheological and mechanical properties accompanying the gradual degradation of the individual polymers were monitored and evaluated (DSC, FTIR, colorimetric method, MFI, tensile impact strength). LDPE and HIPS were found to be more susceptible to thermo-oxidation than HDPE and PP, whereas HDPE and PP were affected to a greater extent by UV exposure; the crucial role here is being played by the stabilization of the studied resins. In HDPE the scission and crosslinking reactions competed both in thermo-and photo-degradation. In the case of LDPE, scission prevailed over branching during thermo-oxidation, whereas photo-oxidation of the same sample led predominantly to crosslinking. Abrupt deterioration of the LDPE rheological properties after one week of thermal exposure was suppressed by re-stabilization. The scission reaction was also predominant for PP during thermo-oxidation, and it took place even faster during UV exposure. In the case of HIPS a slight photo-degradation of PS matrix is accompanied by simultaneous crosslinking of the polybutadiene component.     

Computational prediction of the properties of bis(ethynylthienyl)dialcoxynaphthalene-based conjugated polymers for organic solar cell applications

A series of homo- ( P0 ) and copolymers ( P1-P5 ) based on the electron-donor building-block 2,2′-(2,3-bis(2-ethylhexyloxy)naphthalene-1,4-diyl)bis(ethyne-2,1-diyl)dithiophene (1,4-NET) including ethynyl linkers aiming to promote coplanarity were designed, and their properties predicted using theoretical methodologies to evaluate their potential in organic solar cell applications. The geometries, FMO levels, energy bandgaps, and absorption spectra of trimer models were determined using time-dependent density functional theory, while their photovoltaic and charge-transport properties were estimated by the Scharber's model and semiclassical Marcus theory, respectively. Compared to high-performance conjugated polymers (CPs), such as PTB7-Th or PM6, and similar systems based on the 1D-BDT unit, the HOMO and LUMO levels of P0-P5 tend to be higher. In addition, the new CPs have complementary absorptions with narrow-bandgap acceptors, such as ITIC and Y6, and adequate matches between their HOMO and LUMO levels. Although the simulated photovoltaic and charge-transport properties could be overestimated, the best candidate to be synthesized and tested in organic solar cells is P5 due to its suitable and well-balanced properties, demonstrating the positive effect of incorporating ethynyl bridges to improve the optoelectronic properties of CPs.     

Photo-induced liquid crystal alignment on polyimide containing fluorinated groups

Polyimides were prepared from pyromellitic dianhydride, 4,4'-bis[2-(4-aminophenyl)hexafluoroprop-2-yl]diphenyl ether and 4,4'-diamodiphenyl ether (PMDA-BDAF-ODA) and used for liquid crystal alignment using linearly polarized UV exposure. The alignment properties of a LC on the polyimide films were found to depend on the fluorine content in the PMDA-BDAF-ODA alignment layer and on the UV exposure time. Pretilt angles were obtained in the range 0° to 90° dependent upon the fluorine content in the polyimide film and the UV exposure time. These effects seem to be closely related to the surface energy of the photo-alignment layer.