碘代烷烃分子的C-I断键机理研究

利用离子速度成像方法对碘代直链烷烃和环烷烃分子在267 nm下的光解断键机理进行了研究.实验分析了激发态I*(5p2P1/2)和基态I(5p2P3/2)的离子影像,得到其对应速度、角度分布的各向异性参数β值和相对量子产率Φ(I)和Φ(I*).实验发现碘代直链烷烃和环烷烃分子在吸收一个267nm的光子后,都发生快速的C-I断键,直接解离生成激发态I*和基态I原子.与碘代直链烷烃相比,碘代环烷烃分子具有明显不同的角度分布特征,碘代环烷烃分子基态的β值大于激发态.并且随着α碳原子上所取代的烷基变重,Φ(I*)有变小的趋势.     

丙烯酸酯封端的取代氢键液晶的制备及性能研究

合成了3种丙烯酸酯封端的取代苯甲酸以及其分别与4, 4′-联吡啶和反式吡啶基乙烯自组装形成的双氢键液晶,采用傅立叶红外光谱(FTIR)和核磁共振法(~1H-NMR)表征化合物的结构,使用偏光显微镜(POM)以及差示扫描量热仪(DSC)研究氢键液晶复合体的相转变行为.结果表明,在刚性液晶基元中引入氟原子会增加氢键液晶分子的宽度和降低分子的长径比对液晶材料的性能有很大影响,如降低氢键液晶的熔点以及清亮点等.另外,在柔性链末端引入丙烯酰氧基以及增加液晶基元的长度则会增加液晶分子的长度和规整性,提高氢键液晶复合体的相转变温度.     

外电场下氯甲烷的光谱和解离特性

为了研究外电场对氯甲烷分子光谱和解离特性的影响,采用密度泛函理论（density functional theory,DFT）B3LYP方法在6-311++G（d,p）基组水平上研究了不同外电场（-0.03 a.u.~0.03 a.u.）对氯甲烷分子结构以及解离特性的影响,包括键长、分子能隙、红外光谱以及解离势能面等. 计算结果表明,随着Z方向（C-Cl连线方向）外电场从-0.03 a.u.逐渐增加到0.03 a.u., C-Cl键的键长逐渐增大而C-H键的键长几乎不变, 分子能隙EG先增大后减小,当外加电场等于0.01 a.u.时达到峰值. C-Cl 伸缩（stretching, STR） 振动的频率是逐渐减小的, 而红外光谱（infrared,IR）振动强度是逐渐增加的. 通过进一步计算研究发现, 随着外电场（0~0.03 a.u.）继续增强, CH3Cl分子的势能曲线逐渐降低, 解离能逐渐减小. 当外电场大约是0.04 a.u.时解离能最小,发生解离. 因此,可以通过改变外电场来控制CH3Cl分子的降解.     

硫脲ν_(N-C=S)红外光谱研究

测定硫脲分子N-C=S伸缩振动模式(ν_(N-C=S))的红外光谱(IR)。研究发现:在1500 cm-1~1430 cm-1、1450 cm-1~1350 cm-1和1120 cm-1~1050 cm-1的频率范围内,硫脲分子ν_(N-C=S)分子中分别存在着3个特征谱带,分别归属于ν_(N-C=S)(Ⅰ)-1、ν_(N-C=S)(Ⅱ)和ν_(N-C=S)(Ⅲ)。最后采用二维红外光谱技术(2D-IR)进一步来研究温度变化对于硫脲ν_(N-C=S)红外吸收强度及其变化顺序的影响。本项研究拓展了二维红外光谱技术在ν_(N-C=S)的研究范围。     

中红外AgClBr光子晶体纤维

光子晶体纤维一般为用石英玻璃制作的有孔纤维,它们在3μm～20μm的中红外和远红外光谱范围内是不透明的。最近,以色列Tel-Aviv大学的研究人员利用卤化银(AgClxBr1-x)晶体材料制作出了在上述光谱范围内高度透明的新颖光子晶体纤维。这种光子晶体纤维由两种固体材料构成：其芯为纯AgBr(n=2．16),包层为AgCl(n=1．98)。研究人员对已制成的外径为1mm、长度约为1m的这种软性光子晶体纤维进行了测试。结果表明,其性能与理论模拟非常一致。这种新颖的卤化银光子晶体纤维对于红外激光功率传输、红外辐射测量以及红外光谱学都是极其有用的。     

聚乙烯亚甲基面内摇摆振动二维红外光谱研究

在293~393 K范围内,分别测定聚乙烯的一维红外光谱、二阶导数红外光谱、四阶导数红外光谱和去卷积红外光谱来确定聚乙烯分子结构。进一步采用二维红外光谱研究了聚乙烯亚甲基面内摇摆振动模式(ρCH2)。研究发现,聚乙烯分子中同时存在晶区和非晶区。随着测定温度的升高,聚乙烯分子中ρCH红外吸收强度变化快慢顺序为:720cm-1(ρ2(CH2)crystalline)>731cm-1(ρ(CH2)crystalline)>725 cm-1(ρ(CH2)amorphous)。此项研究显示出二维红外光谱在高分子材料热变性分析中的重大作用。     

乙炔桥键四环异硫氰酸酯液晶化合物的合成及性能

为了研究液晶材料结构与性能的关系,本文以含乙炔桥键的四环异硫氰酸酯化合物为研究对象,芳基硼酸和3-氟-4-溴碘苯为起始原料,经6步反应合成了12种目标化合物,LC纯度大于99%,采用核磁共振、红外光谱对其结构进行了表征。采用DSC和POM对目标化合物的介晶性进行了研究,采用外推法对其双折射率和介电各向异性值进行了测试。结果表明:目标化合物具有300℃以上高清亮点、150℃以上向列相温度区间、0.40~0.51的双折射率以及大于17的介电各向异性值。对于同一系列化合物,随着末端烷基链的增长,化合物熔点降低,但呈现近晶相的趋势增加。在Y、Z位引入侧向氟取代基,熔点和清亮点均降低;X位再引入侧向氟取代基,熔点上升、清亮点下降。用环己烷替代左边第一个苯环,化合物熔点降低、向列相温度区间变宽。引入侧向氟取代基使双折射率下降0.008~0.036。目标化合物有利于提高混合液晶配方的双折射率、清亮点和降低阈值电压。     

用红外激光鉴定分子键

威斯康星 -麦迪逊大学的研究人员将红外激光聚焦到小样品上 ,以获得仅可探测到的分子振动。该技术除传统的红外光谱外 ,还提供分子内不同键或分子间连接的信息。开发者称之为双振动增强(DOVE)四波混频 ,其本质是二维核磁共振光谱术的光学模拟 ,可用于研究生物系统 ,特别是蛋白质等复杂材料。该技术与核磁共振相似 ,将激光调节至两个分子振动的频率处。但它是用激光模拟感兴趣的分子振动 ,可记录分子内和分子间连接的光谱特征。四波混频技术基于这样的作用 :当三束重叠激光在样品中诱发非线性偏振时 ,产生第四个输出波。三个激光频率组合与…     

烷基侧链长度对受体小分子的光伏性能的影响

以苯并二茚并二噻吩(IDT)为给体(D)单元,二氰基茚酮(IC)为受体(A)单元,合成了四个A-D-A型非富勒烯受体小分子。通过调节IDT结构单元上烷基取代基链的长度(-C₆H₁₃,-C₈H₁₇,-C₁₀H₂₁和C₁₆H₃₃),系统研究了分子热学性质、光学性质、能级结构及光伏性能随烷基链长度的变化规律。测试结果表明,烷基链长度的变化对分子的热稳定性、HOMO能级、最大吸收峰值和吸收范围并没有很大的影响,但随着烷基链变短,分子的摩尔消光系数变弱、结晶性升高。基于PBDB-T∶C₈-IDT-IC的光伏器件显示了较高的光电转换效率,达5.90%,而PBDB-T∶C₁₆-IDT-IC的器件效率最低,表明烷基取代基链长度对材料的光伏性能具有一定影响。     

光解与氯自由基的探测

我们利用红外光谱及ESR波谱分析了氯代烃类化合物的光解产物。 红外光谱法检测氯自由基中间体,可以通过辨认酰氯的羰基红外吸收特征峰(1774,1733,875cm~(-1)…     

Effect of Carbon Chain Length in the Substituent of PCBM‐like Molecules on Their Photovoltaic Properties

A series of [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM)‐like fullerene derivatives with the butyl chain in PCBM changing from 3 to 7 carbon atoms, respectively (F1–F5), are designed and synthesized to investigate the relationship between photovoltaic properties and the molecular structure of fullerene derivative acceptors. F2 with a butyl chain is PCBM itself for comparison. Electrochemical, optical, electron mobility, morphology, and photovoltaic properties of the molecules are characterized, and the effect of the alkyl chain length on their properties is investigated. Although there is little difference in the absorption spectra and LUMO energy levels of F1–F5, an interesting effect of the alkyl chain length on the photovoltaic properties is observed. For the polymer solar cells (PSCs) based on P3HT as donor and F1–F5, respectively, as acceptors, the photovoltaic behavior of the P3HT/F1 and P3HT/F4 systems are similar to or a little better than that of the P3HT/PCBM device with power conversion efficiencies (PCEs) above 3.5%, while the performances of P3HT/F3 and P3HT/F5‐based solar cells are poorer, with PCE values below 3.0%. The phenomenon is explained by the effect of the alkyl chain length on the absorption spectra, fluorescence quenching degree, electron mobility, and morphology of the P3HT/F1–F5 (1:1, w/w) blend films.     

Indoline‐Based Molecular Engineering for Optimizing the Performance of Photoactive Thin Films

New indoline dyes ( RK‐1 – 4 ) were designed with a planar geometry and high molar extinction coefficient, which provided surprising power conversion efficiency (PCE) with a thin titanium dioxide film in dye‐sensitized solar cells (DSCs). They had a difference in only alkyl chain length. Despite the same molecular structure, the performance of the respective DSCs varied significantly. Investigating the dye adsorption processes and charge transfer kinetics, the alkyl chain length was determined to affect the dye surface coverage as well as the recombination between the injected photoelectrons and the oxidized redox mediators. When applied to the DSCs as a light harvester, RK‐3 with the dodecyl group exhibited the best photocurrent density, consequently achieving the best PCE of 9.1% with a 1.8 μm active and 2.5 μm scattering layer because of the most favorable charge injection. However, when increasing the active layer thickness, overall device performance deteriorated and the charge collection and regeneration played major roles for determining the PCE. Therefore, RK‐2 featuring the highest surface coverage and moderate alkyl chain length obtained the highest PCEs of 8.8% and 7.9% with 3.5 and 5.1 μm active layers, respectively. These results present a promising perspective of organic dye design for thin film DSCs.     

吖啶酮衍生物粉末微晶的二次谐波测量

建立了有机物粉末二次谐波(SHG)的测量系统。测定了N-烃基口丫啶酮衍生物粉末的SHG,并以溶剂变色法测定了一些口丫啶酮衍生物的分子超极化率与分子基态偶极矩的复合量(βCTμg).从分子结构特征与分子折射率等方面对其所表现出的非线性光学性质进行了分析。具有“Λ”型多极结构、分子间氢键、支化烷基和甲基的口丫啶酮衍生物,粉末SHG较强;βCTμg与SHG相对强度近似线性关系;分子折射率与SHG不满足Kurtz-Pery关系。     

调制转移光谱的最佳吸收程

调制转移光外差光谱信号的信噪比(SNR)和中心斜率与吸收程等有关.采用吸收程微元叠加法———把吸收程分成n段,计算出每一段产生的调制转移光谱信号元,再对n求和得到总的调制转移光谱信号.利用该方法,理论上研究了调制转移光谱信号相对强度及中心斜率随吸收程的变化,得到最佳吸收程.实验上比较了碘池温度为-15℃时一倍程(40 cm),二倍程(80 cm),三倍程(120 cm)和四倍程(160 cm)的光谱信号信噪比和谱线中心斜率,得到三倍程时信号信噪比和谱线中心斜率为最大,估算得到相应的激光稳频精度为9×10-14(1 s积分时间).通过吸收程优化过程获得的调制转移光谱信号用于激光频率稳定控制,有望获得更高的稳频精度.     

Fluorobenzotriazole (FTAZ)‐Based Polymer Donor Enables Organic Solar Cells Exceeding 12% Efficiency

The fluorobenzotriazole (FTAZ)‐based copolymer donors are promising candidates for nonfullerene polymer solar cells (PSCs), but suffer from relatively low photovoltaic performance due to their unsuitable energy levels and unfavorable morphology. Herein, three polymer donors, L24 , L68 , and L810 , based on a chlorinated‐thienyl benzodithiophene (BDT‐2Cl) unit and FTAZ with different branched alkyl side chain, are synthesized. Incorporation of a chlorine (Cl) atom into the BDT unit is found to distinctly optimize the molecular planarity, energy levels, and improve the polymerization activity. Impressively, subtle side chain length of FTAZ realizes a dramatic improvement in all the device parameters, as revealed by the short‐current density (J_sc) improved from 7.41 to 20.76 mA cm^?2, fill‐factor from 36.3 to 73.5%, and even the open‐circuit voltage (V_oc) from 0.495 to 0.790 V. The best power conversion efficiency (PCE) of 12.1% is obtained from the L810‐based device, which is one of the highest values reported for FTAZ‐based PSCs so far. Notably, the corresponding external quantum efficiency curve keeps a very prominent value up to 80% from 500 to 800 nm. The notable performance is discovered from the reduced energy loss, improved molecular face‐on orientation, the down‐shifted energy levels, and optimized absorption coefficient regulated by side‐chain engineering.     

Li+附着CH3-nFnO2过氧自由基:络合物Li+-CH3-nFnO2(n=0～3)结构与性质的研究

采用了从头算分子轨道理论（MP2,非限性的二级微扰理论）和密度泛涵理论（B3LYP）,分别在6-31G（d,p）,6-311G（d,p）,6-311＋G（d,p）,6-311G（2d,p）,和6-311＋G（2df,2p）基组上优化CH3-nFnO2-Li^＋（n=0～3）的几何结构,计算出了相关的NBO电荷分布和锂离子相对于自由基CH3-nFnO2的亲和能。并在同一水平上计算了自由基CH3-nFnO2和络合物CH3-nFnO2-Li^＋的相关伸缩振动频率。CH3-nFnO2在UB3LYP／6-311G（d,P）得到的振动频率与实验值符合得很好．根据相关的文献报道,我们运用从头算分子轨道理论和密度泛涵理论计算出的锂离子相对于CH3-nFnO2的亲和能都能够表明络合物CH3-nFnO2-Li^＋在气态下能以一种稳定的物种形态被离子附着质谱检测．     

Alkyl Substituent Effects on the Conductivity of Polyaniline

The oxidative polymerization of aniline hydrochloride derivatives in water at low temperature is studied without lithium chloride. The resulting polymers have high molecular weight but the conductivity of the acid‐doped films is strongly dependent on the alkyl‐substituted chain at the 2‐positions. The root cause of the alkyl‐substitution effects is thoroughly investigated using density functional theory (DFT) methods (B3LYP using 6–1G(d,p) and 6‐311++G(2d,2p) basis sets). Internal structural changes observed on substitution appear to be more significant than a variety of electronic parameters measured using the natural bond orbital (NBO) method. Interplanar angles steadily increase on substitution, whereas ring orbital properties and the amount of ring delocalization remain fairly constant. An investigation into the extent to which lone pair–σ‐orbital overlap is affected by substitution indicates that increasing the steric bulk of the substituent reduces the ability of the lone pair to delocalize into the ring orbitals. However, the amount of overlap between the two is not adversely affected until the dihedral between them is > 30°, a situation that only occurs in i‐propyl and s‐butyl substitution. This finding is completely reflected in the experimental conductivity measurements.     

Toward the Prediction and Control of Glass Transition Temperature for Donor–Acceptor Polymers

Semiconducting donor–acceptor (D–A) polymers have attracted considerable attention toward the application of organic electronic and optoelectronic devices. However, a rational design rule for making semiconducting polymers with desired thermal and mechanical properties is currently lacking, which greatly limits the development of new polymers for advanced applications. Here, polydiketopyrrolopyrrole (PDPP)‐based D–A polymers with varied alkyl side‐chain lengths and backbone moieties are systematically designed, followed by investigating their thermal and thin film mechanical responses. The experimental results show a reduction in both elastic modulus and glass transition temperature (T_g) with increasing side‐chain length, which is further verified through coarse‐grained molecular dynamics simulations. Informed from experimental results, a mass‐per‐flexible bond model is developed to capture such observation through a linear correlation between T_g and polymer chain flexibility. Using this model, a wide range of backbone T_g over 80 °C and elastic modulus over 400 MPa can be predicted for PDPP‐based polymers. This study highlights the important role of side‐chain structure in influencing the thermomechanical performance of conjugated polymers, and provides an effective strategy to design and predict T_g and elastic modulus of future new D–A polymers.     

Molecular or Nanoscale Structures? The Deciding Factor of Surface Properties on Functionalized Poly(3,4‐ethylenedioxythiophene) Nanorod Arrays

Nanostructures of poly(3,4‐ethylenedioxythiophene) (PEDOT) are assembled by using an anodic aluminum oxide template directly fabricated on gold‐coated silicon wafers. Inside these templates, PEDOT and hydroxy functionalized PEDOT form tubes. On the other hand, alkyl‐ and perfluoro‐functionalized PEDOTs assembled as nanorods. This approach allows a platform to understand the molecular and nanostructural effect on the surface wettability of these materials. In the water/air interface, the contact angle of water droplet (CA_water) for the smooth alkyl‐functionalized PEDOT films increases when alkyl chain gets longer. In contrast, the contact angle reachs saturation at 130° with alkyl chain longer than ethyl in assembled nanorod arrays. It remains the same even in the case of perfluoro‐functionalized PEDOT. Moreover, ethyl‐functionalized PEDOT (PEDOT‐C2) nanorods displays superoleophilicity and the oil deoplet cannot stay on the film in water. Based on the wettability studies, it is concluded that the nanostructures contribute predominantly for the surface wettability of these nanomaterials when the length of alkyl chain crosses certain threshold.