金属电极对聚对苯乙炔电致发光过程的影响

分别采用两种不同功函数的电子注入电极铝(Al)和钙(Ca),构造出了在正常光照下发光可见的单层聚对苯乙炔(PPV)的电致发光器件.发现电极材料的不同使发射光谱产生明显差异,主要表现在550nm的发射峰与510nm发射峰强度的比值不同.通过电致发光(EL)与光致发光(PL)过程的比较,分析了产生这种显著差异的原因.进一步明晰了电流密度与亮度呈线性关系的物理过程.     

聚对苯撑及其烷氧基衍生物的能带研究

利用扩展Hückel分子轨道方法，运用BICON-CEDiT程序包计算了聚对苯撑及其系列烷氧基取代物的一维能带结构.计算结果表明：聚合物的能带结构在很大程度上受到杂原子、侧链等因素的影响，这与已知的实验结果相符；随着烷氧基侧链中C原子数的改变，聚合物的带隙呈现规律性变化.理论计算得到的带隙值与已有的实验观察值符合得相当好.     

碘掺杂聚对苯撑的EPR和σdc

本文对聚对苯撑及其掺碘的样品进行了电子顺磁共振和直流电导率的研究,并分别给出了σdc和EPR谱室温线宽ΔHpp对碘浓度N(I)的变化关系。由于掺杂而诱导的单极化子和双极化子态之间产生极化子跃迁,利用这种跃迁过程解释了此材料的导电性质。从电子顺磁共振的实验结果发现,电子顺磁共振信号与掺碘浓度呈现一种新的现象。试图探讨未掺杂及掺杂的聚对苯撑材料中自旋产生的原因。我们提出了在掺碘后的聚对苯撑材料中,由于碘在材料中以不同形式存在,影响单极化子和双极化子的形成,导致单极化子态和双极化子态之间相互转化的概念。     

聚对苯乙炔的能带结构和关联能计算

在考虑电子-电子相互作用情况下,对基态非简并聚合物聚对苯乙炔（PPV）的长程关联能进行了理论计算,并用长程关联能对带隙进行修正,最后讨论了长程关联能对带隙的影响。在对PPV链的计算中发现,长程关联能先会随着链长N的增加而减小,但当链长大于10后长程关联能会达到饱和。在链长为20个单元的PPV计算中,长程关联能的修正会降低由Hartree-Fock(HF)方法所得的能隙宽度。修正后的能隙宽度能很好的接近实验结果。     

聚对苯乙炔的能带结构和关联能计算

在考虑电子-电子相互作用情况下,对基态非简并聚合物聚对苯乙炔(PPV)的长程关联能进行了理论计算,并用长程关联能对带隙进行修正,最后讨论了长程关联能对带隙的影响.在对PPV链的计算中发现,长程关联能先会随着链长N的增加而减小,但当链长大于10个PPV单元后,长程关联能会达到饱和.与由Hartree-Fock(HF)方法所得的能隙宽度比.长程关联能的修正会使得能隙降低,这种修正后的能隙宽度与实验结果一致.     

聚对苯乙炔的基态、极化子与双极化子激发态及其稳定性

提出了描述聚对苯乙炔(PPV)晶格及电子结构的物理模型,并在该模型的基础上给出了PPV的基态及可能的极化子、双极化子激发态,并对影响激发态稳定性的因素进行了研究. 关键词：     

各种烷氧基取代聚对苯乙炔的合成和发光性能研究

利用脱氯缩合聚合法合成了聚（2－甲氧基－5－丁氧基）对苯乙炔（PMOBOPV），聚（2－甲氧基－5－辛氧基）对苯乙炔（PMOCOPV）和聚（2－丁氧基－5－丁氧基）对苯乙炔（PDBOPV），聚（2－辛氧基－5－辛氧基）对苯乙炔（PD－COPV）4种发光材料。对反应体系的浓度，酸碱度，反应温度及时间等工艺条件和路线进行了细致的研究。结果表明：反应物的纯度，含量对合成产物的产率和性能有较大的影响；碱性是影响脱氯缩合反应的关键因素，而反应温度和时间对缩合反应影响则相对较小，在一定温度下当反应时间达到一定阶段后其转化率基本不变，对合成材料的化学结构，物理性能和发光特性进行了表征和检测。结果显示：非对称烷氧基取代PPV具有良好的溶解性，成膜性和稳定性；而对称性烷氧基取代PPV的溶解性和成膜性相对较差。以PMOBOPV为发光材料，采用旋涂工艺制作出单层和双层发光器件，并对器件的电致和光致发光性能进行了研究。     

聚对苯撑[poly(p-phenylene)]的基态、极化子和双极化子激发态

本文在紧束缚模型基础上,对聚对苯撑类材料提出一简单的哈密顿量,并计算了系统的能带结构,给出基态、极化子、双极化子激发态,得到了双极化子比两个单极化子更容易激发这一重要结论。在能带中除发现能隙内的两个极化子定域能级外,还发现导带和价带都要发生二劈裂,带边上出现浅能级,它们对应的电子态均是定域的。 关键词：     

Polarized Fluorescence of Diphenylhexatriene-Incorporated Poly(Styrene) Film at Room Temperature

Poly(styrene) is a highly viscous, and cross-linked polymer at room temperature. This makes it ideal to use as a molecular fixer. The polarized fluorescence of a diphenylhexatriene (DPH)-incorporated poly(styrene) film has been studied. The excitation and emission wavelength dependence of the anisotropy of fluorescence of a luminophore-incorporated poly(styrene) film reveals that with decreasing excitation wavelength the anisotropy changes remarkably but is independent of emission wavelength. The investigation estimates an angle of no more than 7.4° between the absorption and the emission transition dipole moment for DPH, suggesting poly(styrene) as a suitable medium to evaluate the mutual orientation of absorption and the emission transition dipole moments at room temperature.     

Fluorescence quenching studies of conjugated polymer poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene in the presence of TNT

We report fluorescence quenching of the conjugated polymer poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene (MDMO-PPV) in the presence of nitrated explosives, such as, 2,4,6-trinitrotoluene (TNT). It is found that the conjugated polymer changes color from orange to brownish black when sprayed on traces of TNT within a few seconds. Fluorescence quenching of the conjugated polymer in the presence of TNT is also studied by absorption and emission spectroscopy. The conjugated polymer is highly selective for sensing TNT in daylight and ambient conditions.     

侧链含查尔酮基团的聚(甲基)丙烯酸酯的光交联特性

采用红外光谱、热重分析、紫外光谱和荧光光谱对侧链含查尔酮基团的聚（4-甲基丙烯酰氧基-4'-二甲氨基查尔酮）（PMADMAC）和聚（4-丙烯酰氧基查尔酮）（PAC）的光交联特性进行了研究。随着光照时间的增加,PMADMAC和PAC聚合物光致环加成反应迅速进行,波长短的紫外线更易使得聚合物发生[2+2]环加成反应。与溶液状态相比,固体薄膜状态下的光交联反应速率较慢。PMADMAC聚合物更容易发生光致环加成反应,其光交联速率要比PAC聚合物快,环加成反应也更彻底。采用荧光光谱研究了聚合物的发光特性,发现PAC聚合物无荧光,而PMADMAC聚合物具有溶剂极性敏感的荧光特性。在PMADMAC聚合物的稀溶液中,随着365 nm紫外光照时间的增加,荧光强度迅速降低,其荧光特征波长在紫外光照射后发生蓝移。 PMADMAC和PAC聚合物的热稳定性较好,光交联后形成热不稳定的环丁烷结构,其热稳定性有所降低。     

Isothermal Melt Crystallization Kinetics for Poly(Trimethylene Terephthalate)/Poly(Butylene Terephthalate) Blends

The kinetics of isothermal melt crystallization of poly(trimethylene terephthalate) (PTT)/poly(butylene terephthalate) (PBT) blends were investigated using differential scanning calorimetry (DSC) over the crystallization temperature range of 184–192°C. Analysis of the data was carried out based on the Avrami equation. The values of the exponent found for all samples were between 2.0 and 3.0. The results indicated that the crystallization process tends to be two‐dimensional growth, which was consistent with the result of polarizing light microscopy (PLM). The activation energies were also determined by the Arrhenius equation for isothermal crystallization. The values of ΔE of PTT/PBT blends were greater than those for PTT and PBT. Lastly, using values of transport parameters common to many polymers (U*=6280 J/mol, T _∞=T _g – 30), together with experimentally determined values of T _m ⁰ and T _g, the nucleation parameter, K _g, for PTT, PBT, and PTT/PBT blends was estimated based on the Lauritzen–Hoffman theory.     

Effect of the End Groups and the Solvent on the Gelation of the Hybrid Materials from Poly (Vinyl Chloride) (PVC) and Oligo Phenylene Vinylene (OPV)

Abstract

The role of the end-groups of three oligophenylene vinylene (OPV) and the solvents on the hybrid materials from poly (vinyl chloride) (PVC) and the OPV are examined. The gelation of the three organogel OPVs and of the hybrid materials in bromobenzene and benzyl alcohol was characterized. The morphology, as well as the thermodynamic properties, of these OPV and hybrid materials showed that they depended mostly on the solvent and very little on the different end-groups located on the OPV backbones.     

三螺旋DNA分子poly(dT)·poly(dA)·poly(dT)的构型和振动谱

我们计算了ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）的Ｈｏｗａｒｄ模型的原子笛卡尔坐标，并利用晶格动力学方法对模型进行了简正分析。结果发现其０ Ｐ ０对称振动模式位于８０４ｃｍ－１，这和８１０ｃｍ－１附近没有拉曼和红外谱线的实验结果不符。在８００～１０００ｃｍ－１的范围内只有四个振动模式，明显少于拉曼和红外光谱在该范围内的谱线数目。所以我们认为Ｈｏｗａｒｄ模型需要进一步地完善和修正，ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）必须具有三条不完全一致的脊骨     

Synthesis and Kinetic Study of Thermal Cycloimidization of Novel Poly(Amide Amic Acid) to Poly(Amide Imide) by Thermogravimetric Analysis

A new series of fluorinated poly(amide imide)s (PAIs) were prepared by polycondensation of diamine amic acid (DAA) with isophthaloyl, terephthaloyl, or trimellitic anhydride chloride in dimethylformamide, and their subsequent thermal cycloimidization. DAAs were obtained by reacting 4, 4′ (hexafluoroisopropylidene) diphthalic anhydride (6FDA) with diamines in dimethylformamide at 0–5°C. The kinetics of thermal cycloimidization of poly(amide amic acid) (PAA) to PAIs was investigated by thermogravimetric analysis under isothermal conditions at four different temperatures, i.e. 175, 200, 225, and 260°C, for 75 min. A generalized equation to calculate the theoretical amount of weight loss upon complete imidization, i.e. T_w % = 18Nw/R _Mw, was developed. In the above equation numeral 18 corresponds to the molecular weight of water, N is the number of water molecules, which are eliminated per repeat unit of PAA upon cycloimidization, w is the weight of PAA taken for TGA, and R _Mw is the molecular weight of the repeat unit of PAA. The polymers were characterized by FT-IR spectra. Complete cycloimidization process is discussed in terms of monomer structure (diamines and acid chlorides), effect of imidization temperature and time, types of linkages (meta or para) present, and influence of electron withdrawing groups, such as sulfone, in the monomer structure. It was observed that cycloimidization occurred at a faster rate at the beginning, up to about 30 min, and then proceeded at a slower rate till the end of curing. The thermal and thermooxidative stabilities of PAIs were also investigated in nitrogen and oxygen atmosphere.     

Improving the Barrier Properties of Poly(Lactic Acid) by Blending with Poly(Ethylene-Co-Vinyl Alcohol)

Poly(lactic acid) (PLA)/poly(ethylene-co-vinyl alcohol) (EVOH) blends were prepared via melt blending to improve the barrier properties of PLA. The phase morphologies and final properties (rheological behavior, thermal and dynamical-mechanical features, barrier properties, and mechanical behaviors) of the blends were investigated as a function of the EVOH content. The results indicated that hydroxyl groups of EVOH promoted the degradation of PLA, and thus affected the viscosities and morphologies of the resulting blends. The intrinsic viscosities of PLA in the blends decreased with the content of EVOH. The PLA and EVOH presented typical phase-separated morphologies, with a relatively small domain size of the EVOH phase. The EVOH enhanced the cold-crystallization behavior of PLA. The barrier properties to water vapor and oxygen increased linearly with increasing EVOH content.     

Eu(DBM)_3Phen掺杂聚甲基丙烯酸甲酯静电纺丝荧光纤维

通过静电纺丝技术获得直径约为700 nm,均匀且随机取向的亚微米级Eu(DBM)3Phen/PMMA纤维。在紫外光辐射下,亚微米级荧光纤维发出明亮的红色荧光。其激发光谱表明,荧光纤维有效激发波长范围为200~400 nm。利用积分球配以CCD探测器,在367 nm长波紫外LED激发下对荧光纤维开展绝对光谱功率测试。当LED泵浦功率为535.76#W时,厚度80#m的Eu(DBM)3Phen/PMMA纤维薄层对紫外辐射的吸收率高达89%,350~850 nm范围内发射的总绝对光谱功率、总光子数和总荧光量子产率分别为36.56#W、11.46×10~(13)cps和12.94%。亚微米级Eu(DBM)_3Phen/PMMA纤维薄层中,Eu~(3+)较高的跃迁发射几率及较大的发射截面使得纤维可以高效吸收紫外辐射并转变为可见光,在提高太阳能电池光电转换效率方面具有潜在应用价值。     

High-Pressure Analysis of the Multiple Melting Endotherms of Poly(ethylene succinate) and Poly(butylene succinate)

The origin of the multiple melting peaks in two linear polyesters, poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS), of isothermally crystallized samples was investigated by differential scanning calorimetry (DSC) at atmospheric pressure and high-pressure differential thermal analysis (HP-DTA) at elevated pressures. In PES, the DSC melting curves showed three endothermic peaks at slow heating rates, which decreased to two with increasing heating rates. The HP-DTA curves showed that the area (qualitative) and peak height of the high-temperature peak decreased with increasing pressure and merged with the low-temperature peak at pressures above 450 MPa. This behavior supported the melting, recrystallization, and remelting model for the observed multiple melting endotherms. In PBS, the DSC melting curves were similar to those seen in PES. The HP-DTA curves were also similar to PES up to 400 MPa, but above this pressure the area and the peak height of the high-temperature peak and the temperature difference between the high- and low-temperature peaks remained unchanged. This observation suggested that the two peaks in PBS were due to the melting of two populations of crystals with different lamellar thickness originally present in the sample. The multiple melting behavior in isothermally crystallized PBS is proposed to incorporate both the melting of two populations of crystals and melting, recrystallization, and remelting.