高电荷密度聚苯乙烯微球的制备及胶体晶体组装

以甲基丙烯酸(MAA)为共聚单体,采用无皂乳液聚合法制备了单分散聚(苯乙烯-甲基丙烯酸)共聚微球,再在恒温恒湿条件下采用限制注射法制备出胶体晶体,最后对微球的组成、粒径大小及形态、表面电学性质、胶体晶体的显微形貌进行了测试分析。结果表明:制得的微球粒径均匀,球形度良好且呈单分散性,Zeta电势为–37.2mV;微球组装的胶体晶体排列有序,呈密堆积结构。     

Enhanced power factor of poly (3,4-ethyldioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)/RTCVD graphene hybrid films

The thermoelectric generator has been an attractive alternative power source to operate a wireless sensor node. Usually, inorganic compounds are most often used in thermoelectric devices, and hence, are extensively studied due to their superior thermoelectric performance. We have investigated a novel interfacial technique to fabricate a hybrid film of highly conductive PEDOT:PSS (poly 3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and graphene. Organic materials PEDOT doped with PSS exhibits outstanding electrical properties due to its high conductivity, low bandgap, and energy migration. Furthermore, we utilized graphene fabricated by rapid thermal chemical vapor deposition (RTCVD) as a thermoelectric material. Our results show that the interfacial technique between substrate and hybrid film could be clearly improved due to the UV plasma treatment. The thermoelectric hybrid film of PEDOT:PSS and RTCVD graphene (P/RTG) exhibited an enhanced power factor of 56.28 μW m⁻¹ K⁻² with a Seebeck coefficient of 54.0 μV K⁻¹.     

Bacterial adhesion to toroidal nano-structures from poly(styrene)-block-poly(tert-butyl acrylate) diblock copolymer thin films

Nano-structured thin films with protruding PtBA nanodomain structures were obtained from the deposition, spin-coating, self-assembly and annealing of the diblock copolymer poly(styrene)-block-poly(tert-butyl acrylate) (PS-b-PtBA). The topography has been documented by atomic force microscopy. The sacrificial removal of the PtBA block from these thin film structures after UV irradiation yielded surfaces with 5/7 segmented polystyrene (PS) toroids of 100–150 nm diameter. These polymeric materials (as well as the corresponding homopolymeric materials derived from PS and PtBA) were incubated with Staphylococcus aureus cells. Live and dead cell numbers were determined in replicate trials by fluorescence microscopy after the cells were stained for viability. S. aureus formed colonies of 5–200 cells on the nanodomain and toroid-containing surfaces as assessed by AFM, but only attached sparsely as single cells onto a planar PtBA surface. Cell viability and adhesion was found to be influenced by a combined effect of the surface hydrophilicity and topography. The results demonstrate a synthetic route to produce polymeric surfaces with nano-toroids which are capable of modifying bacterial adhesion.     

Unipolar nonvolatile memory devices with composites of poly(9-vinylcarbazole) and titanium dioxide nanoparticles

Organic-based devices with an 8 × 8 array structure using titanium dioxide nanoparticles (TiO₂ NPs) embedded in poly(9-vinylcarbazole) (PVK) film exhibited bistable resistance states and a unipolar nonvolatile memory effect. TiO₂ NPs were a key factor for realizing the bistability and the concentration of TiO₂ NPs influenced ON/OFF ratio. From electrical measurements, switching mechanism of PVK:TiO₂ NPs devices was closely associated with filamentary conduction model and it was found that the OFF state was dominated by thermally activated transport while the ON state followed tunneling transport. PVK:TiO₂ NPs memory devices in 8 × 8 array structure showed a uniform cell-to-cell switching, stable switching endurance, and a high retention time longer than 10⁴ s.     

Theoretical studies of poly(para-phenylene vinylene) (PPV) and poly(para-phenylene) (PPP)

The electroluminescence from PPV and the blue light emission from PPP constitute exciting subjects of study. The band gap of these semiconducting polymers can be engineered in a wide range from red to ultraviolet by structural changes made on them. In the present work, we present a theoretical approach based on semiempirical and ab initio total energy and force calculations of PPV and PPP. We perform a conformational analysis in order to investigate the connection between their structural, optical and electronic properties. We use the large cell approach, in connection with the semiempirical quantum method Extended Hückel (BICON-CEDiT code) and the density functional theory (DFT) within the full-potential linearized augmented-plane-wave method (FPLAPW) as implemented in the computational code WIEN2k. Our results are compared to other calculations and to optical absorption measurements.     

Effect of water-soluble vitamins on the structure and properties of poly(3,4-ethylenedioxythiopehene):poly(styrenesulfonate)

Intrinsically conducting polymers can have important application in biology because they can be conductive and have good biological compatibility. Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has been the most popular conductive polymer in biological application due to its solution processability in water. PEDOT:PSS can be used as electrode materials or active materials of biological devices or circuits. It is important to study the effect of biomaterials on the structure and properties of PEDOT:PSS films. In this work, water-soluble vitamins that are biomaterials needed for organisms are used to treat PEDOT:PSS. They can significantly enhance the conductivity of PEDOT:PSS from 0.3 S cm⁻¹ up to higher than 1000 S cm⁻¹. The conductivity enhancement depends on the structure of vitamins. The highest conductivity enhancement was observed for PEDOT:PSS treated with vitamin B3. The vitamin-induced changes in the structure and properties of PEDOT:PSS were studied by UV–Vis absorption spectroscopy, temperature-dependence of resistance measurements, atomic force microscopy and cyclic voltammetry. The characterizations indicate that vitamins can induce phase segregation between PEDOT and PSS and the conformational change of the PEDOT chains. These discoveries are important to understand the application of PEDOT:PSS in biology and the development of new biological application of PEDOT:PSS.     

Novel electrochromic and infrared emissivity modulation films based on poly(carbazoyltriphenylamine) and poly(carbazoyltriphenylamine-thiophene)

Synthesis and characterizations of novel conducting polymer film based on poly(carbazoyltriphenylamine) (poly(CBZ-TPA)) were studied. Additionally, copolymer film based on CBZ-TPA and thiophene (Th) was also obtained by electrochemical polymerization. Electrochromic properties of poly(CBZ-TPA) and poly(CBZ-TPA-Th) films were investigated by cyclic voltammetry and double step potential chronoamperometry. Optical properties of the two films were characterized by UV–vis spectrophotometer and FT-IR spectrometer. Different colors of poly(CBZ-TPA) film were achieved, which exhibits as camel gray (at −0.5 V), light gray (at 0 V) and army green (at 1.6 V). The maximum UV–vis absorption difference of poly(CBZ-TPA) film is about 15.83% in the visible region when applied with the voltage between 0 V and 1.6 V, and the coloring and bleaching time are 1.8 s and 1.0 s, respectively. The biggest different average IR-emissivity modulation of poly(CBZ-TPA) film is 0.37 in the wavelength regions of 8–14 μm. The copolymerization film of thiophene with CBZ-TPA has a distinct effect on the electrochromic performance of poly(CBZ-TPA) film. Compared with poly(CBZ-TPA) film, poly(CBZ-TPA-Th) film shows different colors, which exhibits as maize-yellow (at −0.5 V), milk white (at 0 V) and dark green (at 1.4 V). The maximum UV–vis absorption difference of poly(CBZ-TPA-Th) film is about 23.30% in the visible region between 0 V and 1.4 V, but it has a slower response speed (coloring and bleaching time are 3.0 s and 4.0 s, respectively). However, the biggest different average IR-emissivity modulation of poly(CBZ-TPA-Th) film reaches up to 0.41 in the wavelength regions of 8–14 μm compared to that of poly(CBZ-TPA) film.     

Preparation of lateral spin-valve structure using doped conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)

To perform four-terminal nonlocal spin-valve measurements on organic spin-valves, we fabricated lateral spin-valve devices consisting of doped conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) [PEDOT:PSS] and ferromagnetic Ni₈₀Fe₂₀ narrow line (width: 530 nm) electrodes. Although the formula of the nonlocal magnetoresistance with the parameters of doped conducting polymers predicts sufficient nonlocal magnetoresistance, we could not observe any spin signal. The spin diffusion length in the doped PEDOT:PSS device does not appear to be as long as those predicted by both the Elliott–Yafet mechanism and the theory of spin relaxation in organic disordered solids.     

Indium zinc oxide ohmic contact to poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) induced by UV light

In this research, we investigated the I–V characteristics of ITO/PEDOT:PSS/InZnO devices for two sets of samples. The first set is composed of PEDOT:PSS as-prepared, while the second set is composed of PEDOT:PSS irradiated by UV light source. We found that UV irradiation improves the electrical conductivity of the fabricated devices and yields to ohmic contact. Based on the UPS measurements, it was found that UV irradiation leads to an increase in the work function and the enhancement of electrical conductivity of PEDOT:PSS films. XPS and AFM measurements indicate that conformational changes of the PEDOT:PSS films are responsible for this behavior. We also studied the effect of storage on the electrical properties of our devices. No significant changes of electrical characteristics have been found after storing the devices for a period of 30 days.     

Determination of the electroaffinity and potential barrier heights at polymer/ metal interfaces of poly(4,7-benzothiophene vinylene) (PBTV)

In this paper we determine the LUMO level position of poly(4,7-benzothiophene vinylene) (PBTV), a heterocyclic poly(phenylene vinylene) (PPV) analogue, using tunnelling current measurements. We compare the energy level positions with those measured for PPV and determine their shifts. The experimental results are compared with theoretical predictions and good agreement is observed. © 1998 John Wiley & Sons, Ltd.     

Electrical characterization of inorganic-on-organic diode based InP and poly(3,4-ethylenedioxithiophene)/poly(styrenesulfonate) (PEDOT:PSS)

The electronic properties of metal–organic semiconductor-inorganic semiconductor diode between InP and poly(3,4-ethylenedioxithiophene)/poly(styrenesulfonate) (PEDOT:PSS) polymeric organic semiconductor film have been investigated via current–voltage and capacitance–voltage methods. The Al/PEDOT:PSS/p-InP contact exhibits a rectification behavior with the barrier height value of 0.98 eV and with the ideality factor value of 2.6 obtained from their forward bias current voltage (I–V) characteristics at the room temperature greater than the conventional Al/p-InP (0.83 eV, n = 1.13). This increase in barrier height and ideality factor can be attributed to PEDOT:PSS film formed at Al/p-InP interface.     

P(VDF-TrFE)/Ag复合薄膜的铁电以及介电性能研究

利用旋涂法制备并采用氢气退火处理得到P(VDF-TrFE)/Ag复合薄膜,在XRD图像上可以观察到在2θ=38.1°的Ag(111)相的衍射峰,同样在SEM图像上观察到银纳米粒子的存在.在薄膜的红外透射光谱上可以观察到β相特征峰的蓝移,这可归结为银纳米粒子与偶极子的相互作用.银纳米粒子的掺杂增强了薄膜的铁电和介电性能.与传统退火方式处理的纯P(VDF-TrFE)薄膜相比,纳米银掺杂比例为10％的P(VDF-TrFE)/Ag复合薄膜的铁电剩余极化强度和介电常数分别提高了32.5％和13.3％.介电损耗不随纳米银掺杂比例的增加而变化的现象不符合渗流理论.     

P(VDF-TrFE)/Ag复合薄膜的铁电以及介电性能研究

利用旋涂法制备并采用氢气退火处理得到P(VDF-TrFE)/Ag复合薄膜,在XRD图像上可以观察在2θ=38.1?的Ag(111)相得衍射峰,同样在SEM图像上观察到银纳米粒子的存在。在薄膜的红外透射光谱上可以观察到β相特征峰的蓝移可归结为银纳米粒子与偶极子的相互作用。银纳米粒子的掺杂增强了薄膜的铁电和介电性能。介电损耗随着掺杂比例的增加而降低的趋势不符合渗流理论。     

Synthesis and characterization of poly (linoleic acid)-g-poly(methyl methacrylate) graft copolymer with applying in Au/PLiMMA/n-Si diode

Poly (linoleic acid)-g-poly(methyl methacrylate) (PLiMMA) graft copolymer was synthesized and characterized. PLiMMA graft copolymer was synthesized from polymeric linoleic acid peroxide (PLina) possessing peroxide groups in the main chain by free radical polymerization of methyl methacrylate. Later, PLiMMA was characterized by proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Furthermore, Au/PLiMMA/n-Si diode was fabricated for the purpose of investigating PLiMMA׳s conformity in diodes. The main electrical characteristics of this diode were investigated using experimental current–voltage (I–V) measurements in dark and at room temperature. Obtained results, such as sufficiently high rectifying ratio of 4.5×10⁴, indicate that PLiMMA is a promising organic material for electronic device applications.     

Dielectric function and degradation process of poly(triarylamine) (PTAA)

We investigated the optical properties and the degradation process of the organic p-type semiconductor poly(triarylamine) (PTAA) in the mid infrared region. The dielectric function of PTAA was determined in the spectral region of 700 up to 6000 cm⁻¹ by modeling ellipsometric measurements. Due to degradation at 65 °C, PTAA thin films developed carbonyl and hydroxyl features in the infrared spectra. Degradation under 85% RH additionally led to absorption signals of water. A degradation of the bare gold substrates was also observed. For bare gold films, morphology changed upon degradation and adsorption of hydrocarbons from the ambience took place.     

pn+ junction in an implanted electroactive polymer:poly(paraphenylene)

The authors have recently shown that specific and stable n or p doping may be obtained on poly(paraphenylene), providing moderate implantation conditions with appropriate ions are used. Here they describe a pn⁺-junction made in intrinsic insulating poly(paraphenylene) (α<10^-12 Ω^-1 cm^-1) by implantation (E≃50 keV) of alkali metal ions (essentially caesium for n doping) and halogen (iodine for p doping)     

Photosensitive poly(dimethylsiloxane) materials for microfluidic applications

Poly(dimethylsiloxane) (PDMS) is used as a thermally crosslinked material in microfluidics and Bio-MEMS. Recently photo-patternable materials show increasing interest, as the demand for easy alignment arises for multilayered structures. We present a photopatterning process for PDMS in microfluidics, for two main uses: (a) as a thin (approximately 10 μm) structural layer, and (b) as a very thin (approximately 1 μm) hard mask for oxygen plasma etching of microfluidic polymeric substrates down to several tens of microns. We study the deep-UV and I-line photocrosslinking properties of siloxane copolymers containing vinyl-methyl-siloxane groups as polymerizable units. These materials are sensitive to DUV and can be sensitized to 300–400 nm using free radical initiators. We prove that even thermally curable PDMS (Sylgard 184, base) can become photosensitive in DUV, although its practical use is limited to very thin films, due to its small molecular weight.     

Facile and rapid production of conductive flexible films by deposition of polythiophene nanoparticles on transparent poly(ethyleneterephthalate): Electrical and morphological properties

In this work, polythiophene (PTh) nanoparticles were successfully deposited on poly(ethyleneterephthalate) (PET) substrate as thin film by a facile and rapid chemical oxidative deposition method using a binary organic solvent system in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTAB) as cationic surfactant. The electrical conductivity of PTh nanoparticles deposited on PET was optimized by adjusting the surfactant/oxidant/monomer molar ratio, monomer concentration and time of polymerization. Resulted film was conductive, transparent and flexible which can be used in electronic devices such as OLEDs. Electrical conductivity for the un-doped deposited PTh nanoparticles at oxidant/monomer molar ratio of 5:1 at 0 °C polymerized for 12 min was measured to be 1.18×10⁻² S/cm. The effect of oxidant and monomer concentration on polymerization yield was also investigated. The structural confirmation and transparency of the PTh nanoparticle coated PET films were characterized by FTIR and UV–vis spectroscopy, respectively. Field emission scanning electron microscopy (FESEM), laser particle size analysis and transmission electron microscopy (TEM) were employed for surface morphology and size distribution measurements of PTh nanoparticles. The results showed that the PTh nanoparticles are deposited as globular aggregates with average size of about 50 nm on PET.     

（英）界面极化层引起P(VDF-TrFE)电容器的电容-电压的不对称

通过研究Au/P(VDF-TrFE)/Al 电容器的变温(200 K 到310 K)电容-电压曲线,室温下观察到两个极化方向下的电容不对称,这个现象可以应用于非挥发性存储器.电容不对称程度随着温度的降低而变小,当温度低于230 K,电容不对称现象消失.P(VDF-TrFE)与Al电极之间的界面极化层可以解释观察到的电容不对称现象.