Calculation of near-field molecular interactions in polymers

The role of near-field and far-field interactions in determining the conformative mobility of macromolecules is analyzed here. An algorithm is proposed for finding the global minimum energy of near-field intramolecular interactions.     

Novel mucoadhesive system based on sulfhydryl-acrylate interactions

We propose a novel cross-linked mucoadhesive system that can interact covalently with mucin type glycoprotein, thus providing both strong bonding to mucosa as well as ability to function as a sustained release matrix. The strong bonding results from Michael type addition reaction between an acrylate end group on a polymer and the sulfide end group of the mucin type glycoprotein. A proof of concept is provided using a polyehtylene glycol hydrogel formed in situ from polyehtylene glycol di-acrylate (PEG-DA) macromers. The ability of PEG-DA to create interactions with mucin type glycoproteins was verified using nuclear magnetic resonance (NMR) and rheology experiments. NMR studies have detected disappearance of the PEG-DA’s vinyl protons upon mucin addition, whereas rheology measurements have shown a viscosity increase. These results provide an evidence for the formation of mucin-polymer covalent bond. The ability PEG-DA to attach to mucus and promote mucoadhesion was evaluated by tensile measurements. PEG-DA adhered at strength comparable to other covalently interacting mucoadhesive polymers. Furthermore, PEG-DA was found to be a suitable candidate for sustained release of the hydrophilic drug Ibuprofen.     

基于红光染料掺杂的有机电压调制发光器件

制备了一种电压调制有机发光二极管(OLED),结构为ITO/CuPc(10nm)/NPB(70nm)/MADN(30nm)/MADN:DCM(2%(质量分数),10nm)/BCP 7nm/ALQ(30nm)/LiF(0.5nm)/Al(100nm).通过调节DCM的掺杂浓度和MADN:DCM厚度,发光颜色发生了随电压的连续变化.该器件的起亮电压在3V左右,当驱动电压为16V时最大亮度达到16652cd/m2,电流效率在8V时达到最大为5.78cd/A.     

分子取向调控对有机太阳电池器件性能的提升

活性层形貌对有机太阳电池的器件效率有着重要的影响。调控活性层中的分子取向是优化其形貌的方式之一。本文旨在采用Layer-by-Layer (LbL)的方法调控有机太阳电池活性层中分子的取向,进而提升电池器件的效率。通过向电子受体中加入不同的添加剂实现活性层中受体分子(Y6)的取向调节,优化后器件的能量转换效率达到16.2%。利用椭圆偏振光谱和掠入射广角X射线散射(GIWAXS)技术对活性层薄膜进行了表征,结果表明,向受体中加入1, 8-二碘辛烷(DIO)作为添加剂后,活性层中的Y6分子倾向水平取向,向受体中加入氯萘(CN)作为添加剂后,Y6分子倾向于垂直取向。电学和光学表征结果表明,Y6的水平取向增加了器件内激子的分离效率,进而提升了器件的能量转换效率。     

Control of the molecular interaction in the emitting layer of organic light-emitting device

The molecular interactions and their effects on the emission properties of organic LED are reviewed. Improvements of the device characteristics are demonstrated in some system with various molecular interactions. Then, it was possible to obtain simultaneously high luminescence efficiency and high charge mobilities by introducing the special molecular interaction in the emitting layers of LED.     

Hybrid organic/inorganic molecular heterojunctions based on strained nanomembranes

In this work, we combine self-assembly and top-down methods to create hybrid junctions consisting of single organic molecular monolayers sandwiched between metal and/or single-crystalline semiconductor nanomembrane based electrodes. The fabrication process is fully integrative and produces a yield loss of less than 5% on-chip. The nanomembrane-based electrodes guarantee a soft yet robust contact to the molecules where the presence of pinholes and other defects becomes almost irrelevant. We also pioneer the fabrication and characterization of semiconductor/molecule/semiconductor tunneling heterojunctions which exhibit a double transition from direct tunneling to field emission and back to direct tunneling, a phenomenon which has not been reported previously.     

Preparation and characterization of high molecular weight low bandgap polymers based on poly(2,7-carbazole)s for organic solar cells

We report the PCDTBT {Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]}, an alternating copolymer of 2,7-carbazole and dithienyl-2,1,3-benzothiazole, has high molecular weight and narrow molecular weight distribution. Our PCDTBT can be successfully prepared as good yield by using tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] catalyst instead of Pd2dba3/P(o-Tol)3 catalyst. From the UV/Vis absorption spectroscopy, we can observe that absorption bands of PCDTBT are bathochromically shifted by increasing the molecular weight, that is to say, our high molecular weight PCDTBT can absorb much longer wavelength light compare to low molecular weight PCDTBT. The best performance can be obtained from device based on the mixture of PCDTBT (polymer-30) and PC70BM {[6,6]-phenyl C71-butyric acid methyl ester} (1:4) as an active layer, which shows 4.50% of PCE with 10.1 mA/cm2 of short-circuit current density (J(SC)), 0.85 V of open-circuit voltage (V(OC)), and 52.3% of fill factor which is very similar with Leclerc's published result.     

Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates

Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. In the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T_g, and this must be due to covalent matrix-nanofiber linkages.     

Quartz crystal microbalance sensor for organic vapor detection based on molecularly imprinted polymers

Molecularly imprinted polymers on quartz crystal microbalances (QCM) are examined for their ability to detect vapors of small organic molecules with greater sensitivity and selectivity than the traditional amorphous polymer coatings. Hydroquinone and phenol serve as noncovalently bound templates that generate shape-selective cavities in a poly(acrylic) or poly(methacrylic) polymer matrix. The imprinted polymers are immobilized on the piezoelectric crystal surface via a precoated poly(isobutylene) layer. The behavior of the imprinted polymer films is characterized by the dynamic and steady-state response of the QCM frequency to pulses of organic vapors in dry air. The apparent partition coefficients are determined for imprinted and nonimprinted polymers prepared by two synthetic methods and for varying mole ratios of template to monomer. The hydroquinone-imprinted polymers and, to a lesser extent, the phenol-imprinted polymers exhibit greater sensitivity and higher selectivity than the nonimprinted polymers toward organic vapors that are structurally related to the templates. These results indicate that molecularly imprinted polymers are promising for the development of selective piezoelectric sensors for organic vapor detection.     

一种新型基于纳米TiO2薄膜的电子纸器件

近年来,在电致变色领域基于甲基紫精修饰高比表面积的纳米TiO2薄膜电极取得了巨大的进步,并将这项技术推向商业化.本文介绍了一种由有机变色分子修饰纳米晶TiO2薄膜电极而组装成的电致变色器件,通过"嫁接"在甲基紫精分子上的磷酸基和纳米TiO2薄膜电极表面的羟基化学吸附,我们得到了具有良好电致变色性能的"电子纸".本文采用的电解质是0.05mol/L的高氯酸锂和0.05mol/L的二茂铁的1,4丁内酯溶液,对电极为透明导电玻璃.实验证明该电致变色器件具有很高的稳定性,并达到了毫秒级的响应速度,在未来显示领域"电子纸"的商业化进程中具有很大的潜力.     

非线性光学有机聚合物材料研究进展

非线性光学有机聚合物材料在光通信、高密度光存储、及全光信息处理等高技术领域中的应用前景已引起广泛关注。在简要介绍非线性光学效应的基础上,主要论述了有机聚合物非线性光学材料的研究发展及其应用。同时,根据实用化器件对材料的要求及目前存在的主要问题提出解决方案。     

Novel nonlinear optical materials based on dihydropyridine organic chromophore deposited on mica substrate

We have synthesized novel composites based on a 1-methyl-4-[2-(3-methoxy-4-oxocyclohexadienyliden)ethyliden]-1,4-dihydropyridine chromophore incorporated into a polymer PMMA host (weight content of 7.5%) deposited on the mica substrate. In the result of simultaneous application of external dc-electric field and thermal heating we have measured values of second order optical effect of about 122 pm/V at 1,064 nm fundamental laser wavelength. This effect show very weak reversibility after the dc-field switching off. Optical properties of the embedded compound were elucidated by means of IR–LD spectroscopy of oriented colloids in nematic host. UV-spectroscopy, 1H- and 13C-NMR methods were also used. Quantum chemical calculations have been carried out in order to describe electronic structure and optical properties.     

Modulation of the sensitive temperature range of fluorescent molecular thermometers based on thermoresponsive polymers

Fluorescent molecular thermometers based on polymers showing a temperature-induced phase transition and labeled with polarity-sensitive fluorescent benzofurazans are the most sensitive known. Here we show a simple and effective method for modulating the sensitive temperature ranges of fluorescent molecular thermometers based on such temperature-responsive polymers. 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole was adopted as a polarity-sensitive fluorescent benzofurazan, and nine copolymers of two kinds of acrylamide derivative (N-n-propylacrylamide, N-isopropylacrylamide, and/or N-isopropylmethacrylamide) with a small amount of DBD-AE were obtained. The fluorescence intensities of these copolymers in aqueous solution sharply increased with increasing temperature over a small range (6-7 degrees C). In contrast, these fluorescent molecular thermometers differed from one another in the sensitive temperature range (between 20 and 49 degrees C). Moreover, the sensitive temperature ranges were well related to the acrylamide ratios in feed. In addition, the responses from these fluorescent molecular thermometers to the change in temperature were reversible and exactly repeatable during 10 cycles of heating and cooling (relative standard deviation of the fluorescence intensity, 0.44-1.0%).     

Role of contact electrification and electrostatic interactions in gecko adhesion

Geckos, which are capable of walking on walls and hanging from ceilings with the help of micro-/nano-scale hierarchical fibrils (setae) on their toe pads, have become the main prototype in the design and fabrication of fibrillar dry adhesives. As the unique fibrillar feature of the toe pads of geckos allows them to develop an intimate contact with the substrate the animal is walking on or clinging to, it is expected that the toe setae exchange significant numbers of electric charges with the contacted substrate via the contact electrification (CE) phenomenon. Even so, the possibility of the occurrence of CE and the contribution of the resulting electrostatic interactions to the dry adhesion of geckos have been overlooked for several decades. In this study, by measuring the magnitude of the electric charges, together with the adhesion forces, that gecko foot pads develop in contact with different materials, we have clarified for the first time that CE does contribute effectively to gecko adhesion. More importantly, we have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.     

Fluorescent molecular thermometers based on polymers showing temperature-induced phase transitions and labeled with polarity-responsive benzofurazans

Poly(N-isopropylacrylamide) in aqueous solution undergoes a phase transition at approximately 32 degrees C. The fluorescence properties of benzofurazans are affected by solvent polarity. We combine these two characteristics for the first time to develop sensitive fluorescent molecular thermometers. Five fluorescent monomers having a benzofurazan skeleton were synthesized, and the copolymers of N-isopropylacrylamide (NIPAM) and a small quantity of the fluorescent monomer were obtained to investigate their fluorescence properties. With increase in temperature, the copolymers in water showed the temperature-induced phase transition at approximately 32 degrees C and the fluorescence intensities of the copolymers concurrently increased. Especially, for the copolymer of 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole and NIPAM, the fluorescence intensity at 37 degrees C was 13.3-fold that seen at 29 degrees C. The sensitive range of temperature of these fluorescent molecular thermometers is changed by the replacement of the NIPAM units by N-isopropylmethacrylamide or N-n-propylacrylamide units in the copolymers. The basis of these fluorescent molecular thermometers is the decrease in the microenvironmental polarities near the main chains of the copolymers with increasing temperature, as confirmed from the maximum emission wavelengths of the benzofurazan units in the copolymers. The responses from the copolymers to the change in temperature are reversible and exactly repeatable during at least 10 cycles of heating and cooling.