Understanding rate‐limiting processes for the sublimation of small molecule organic semiconductors

Organic small molecules continue to gain attention for application in light‐emitting devices in displays and solid‐state lighting. The purification of these materials by sublimation represents a critical obstacle for their high throughput processing. In this work, we find that the purification of the archetypical hole‐transporting material N,N′‐bis(naphthalen‐1‐yl)‐N,N′‐bis(phenyl)‐benzidine (α‐NPD) is controlled by a combination of viscous flow, Knudsen diffusion, and physical vapor deposition. In contrast with other commercially practiced sublimations, steps like diffusion within the solid feed, desorption from the feed particle surface, and mass transfer within the bed of feed particles, do not significantly affect the sublimation rate. This work provides guidelines for the large‐scale purification of organic semiconductor materials, and possibly for a broader range of high value small molecule specialty materials. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1347–1354, 2014     

Organic materials for organic electronic devices

In recent years, organic electronic devices which use organic materials as an active layer have gained considerable interest as light-emitting devices, energy converting devices and switching devices in many applications. In these organic electronic devices, the organic materials play a key role of managing the device performances and various organic materials have been developed to improve the device performances of organic electronic devices. In this paper, recent developments of organic electronic materials for organic light-emitting diodes and organic solar cells were reviewed.     

Orientation control of regioregular‐poly(3‐dodecylthiophene) films formed by the friction‐transfer method and the performance of organic photovoltaic devices based on these films

Control of the molecular orientation of regioregular poly(3‐alkylthiophene)s (RR‐P3ATs) improves the performance of field‐effect transistors and organic photovoltaic devices (OPVs). However, most thiophene ring planes of the RR‐P3AT molecules (except RR‐poly(3‐butylthiophene)) in films formed by the conventional spin‐coating method stand on the substrate, that is, edge‐on orientation. Orientation control of RR‐poly(3‐dodecylthiophene) (RR‐P3DDT) molecules in films formed by the friction transfer method is reported and the performance of OPVs based on friction‐transferred RR‐P3DDT films is compared to that of OPVs based on spin‐coated films. The films are investigated by polarized ultraviolet–visible light absorption spectroscopy, Fourier transform infrared spectroscopy, and grazing‐incidence X‐ray diffraction measurement. For friction‐transferred films, the RR‐P3DDT molecular chain is uniaxially aligned parallel to the substrate plane. In addition, the thiophene ring planes of the RR‐P3DDT molecules are also oriented parallel to the substrate plane, that is, face‐on orientation. The power conversion efficiency (PCE) and fill factor of the RR‐P3DDT/C₆₀ bilayer OPVs based on the friction‐transferred RR‐P3DDT films are higher than those of devices based on spin‐coated films. The PCE and photocurrent of the device based on the friction‐transferred film are larger under irradiation with polarized light parallel to the RR‐P3DDT molecular chain direction than with polarized light orthogonal to the chain direction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40136.     

Thermal stability and chemical durability of PVC‐based biomedical devices

Poly(vinyl chloride) (PVC)‐based blood circuits for extracorporeal hemodialysis were investigated for the assessment of their thermal stability as well as their chemical durability towards ionizing radiation sterilization and environmental conditions of storage and transportation. Thermal degradation was monitored by measuring the amount of hydrochloric acid (HCl) evolved as a function of different thermal stresses. HCl was extracted from the internal lumen of the blood circuits, and then quantitatively evaluated under the corresponding form of chloride ions by chromatographic technique (HPLC‐IC). Behavior of PVC heat stabilizers was evaluated as well, determining also the concentration of calcium and zinc released by the investigated materials, by flame atomic absorption spectroscopy (FAAS) technique. Electron beam irradiation revealed an impact on blood tubing higher than that of environmental storage conditions. Nevertheless, real operative cases of sterilization and storage conditions turned out to be quite safe, and all blood circuits displayed good performances in terms of thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5378–5387, 2006     

Theoretical investigations of electronic structure and charge transport properties in polythiophene‐based organic field‐effect transistors

Regioregular poly(3‐hexylthiophene) (P3HT) is a hole transport polymer material used in organic field‐effect transistors (OFETs) and can reach mobilities as high as 0.1 cm² V^?1 s^?1. Factors that affect the charge mobility and the transport mechanisms of P3HT‐based OFET systems are therefore of great importance. We use quantum mechanical methods to interpret the charge mobility and the transport properties of self‐assembled P3HT molecules along the intra‐chain and inter‐chain directions. Our approach is illustrated by a hopping transport model, in which we examine the variation of charge mobility with torsional angle and the intermolecular distance between two adjacent thiophene segments. We also simulate packed P3HT structures via molecular dynamics (MD) simulations. The MD results indicate that the resultant mobility along the π?π inter‐chain direction is significantly less than that along the intra‐chain direction. Accordingly, the main charge‐transfer route within the P3HT ordered domains is an intra‐chain rather than an inter‐chain one. The calculation result for the inter‐chain hole mobility is around 10^?2 cm² V^?1 s^?1, which is consistent with experimental data from P3HT single fibril. Copyright © 2009 Society of Chemical Industry     

Conjugated polyelectrolytes: A new class of semiconducting material for organic electronic devices

This feature article presents a short review of the recent developments in the synthesis of conjugated polyelectrolytes (CPEs) along with their applications in organic optoelectronic devices with particular focus on the molecular structures of CPEs with ionic functionality, synthetic approaches, and their utilization as an interfacial layer. The orthogonal solubility of the CPEs allows the simple preparation of multilayer organic devices by solution casting on top of a nonpolar organic photoactive layer without disturbing the interfaces, showing their effectiveness in tuning the electronic structures at the interfaces for improving the charge carrier transport and resulting device properties. These achievements highlight the dynamic nature of CPEs and their applicability to a wide range of optoelectronic devices.     

Towards self‐sterilizing medical devices: controlling infection

Medical devices are an important component of modern medicine. In many cases, medical devices are used to improve the ‘quality of life’ for the patient, and their use is increasing dramatically. At the same time, the emergence of multi‐drug‐resistant bacteria, or ‘super‐bugs’, is a global crisis. At least in part, biomedical devices proliferate the growth of resistant bacteria. This has spurred new research aimed at the development of medical devices that prevent or control bacterial colonization, and this perspective discusses the current efforts in this area. Copyright © 2008 Society of Chemical Industry     

Integrated energy storage system based on triboelectric nanogenerator in electronic devices

The emergence of electronic devices has brought earth-shaking changes to people's life.However,an extemal power source may become indispensable to the electronie devices due to the limited capacity of batteries.As one of the possible solutions for the extermal power sources,the triboelectric nanogenerator(TENG)provides a novel idea to the increasing mumber of personal electronic devices.TENG is a new type of energy ollector,which has become a hot spot in the field of nanotechnology.It is widely used at the acquisition and conversion of mechan-ical enegy to electrice energy through the principle of electrostatic induction.On this basis,the TENG could be integrated with the energy stonage system into a self-powered system,W hich can supply power to the electronic devices and make them work continuously.In this review,TENG's basic structure as well as its working process and working mode are firstly discussed.The integration method of TENGs with enegy storage systems and the related research status are then introduced in detail.At the end of this paper,we put forward some problems and discuss the prospect in the future.     

有机小分子电致发光材料及器件的研究进展

综述了以有机小分子发光材料为基础的红绿蓝和白光有机发光二极管的结构、发光性质,简要介绍了其应用前景和发展趋势。     

Polyaniline/Poly(acrylamide‐co‐sodium acrylate) Porous Conductive Hydrogels with High Stretchability by Freeze‐Thaw‐Shrink Treatment for Flexible Electrodes

With the development of alternatives to traditional fossil energy and the rise of wearable technology, flexible energy storage devices have attracted great attention. In this paper, a polyaniline/poly(acrylamide‐sodium acrylate copolymer) hydrogel (PASH) with high flexibility and excellent electrochemical properties for flexible electrodes is fabricated by freeze‐thaw‐shrink treatment of a highly water‐absorptive hydrogel, together with in‐situ polymerization of aniline at a low aniline concentration (0.1 mol L^?1). The PASH exhibits a conductivity of 4.05 S m^?1 and an elongation at break of 1245%. The freeze‐thaw‐shrink treatment greatly improves the electrochemical performance and stability of the conductive PASH. The area specific capacitance of PASH reaches 849 mF cm^?2 and the capacitance maintains 89% after 1000 galvanostatic charge–discharge cycles. All the raw materials are conventional industrialized materials and no additional templating agent is needed during the entire synthesis process. This study provides a cost‐efficient approach for the fabrication of conductive polymer hydrogels, which has a broad application prospect in flexible energy storage electronic devices.     

Moving ion fronts in mixed ionic‐electronic conducting polymer films

The aim of this paper is to analyze moving front dynamics of ions and holes in a planar, mixed ionic‐electronic conducting polymer film. As cations invade the film, holes evacuate; thus, an ionic current is converted to an electronic signal. Recent experiments show that the location of the advancing ion front increases as the square‐root of time, a scaling typically associated with diffusive transport, which is surprising given the large driving voltages utilized. Ionic and electronic transport is modeled via the drift‐diffusion equations. A similarity transformation reduces the governing partial differential equations to ordinary differential equations that are solved numerically. The similarity transformation elucidates the origin of the square‐root‐of‐time front scaling. The similarity solution is then compared to the numerical solution of the full drift‐diffusion equations, finding excellent agreement. When compared with experimental data, our model captures the front location; however, qualitative differences between the ion profiles are observed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1447–1454, 2015     

Surfactant‐free microdispersion process of gas in organic solvents in microfluidic devices

The scaling of bubble/slug formation in organic solvents at microscale without surfactant was initially investigated by using T‐junction and symmetrically cross‐shaped microfluidic devices. Four unique organic solvents and three dispersion methods were used, forming different flow patterns and dispersion size. The flow pattern of uniform slug flow was investigated. Both the gas–liquid flow and dispersion size, which ranged from 400 to 1400 μm in length and 270 to 430 μm in diameter, depended on several factors including dispersion method, two‐phase flow rates, physical properties of the liquid phase, and structure of microchannels. A general equation L/w = k(Q_G/Q_L)^αCa^β was used to characterize the dispersion size with modification of Q_G/Q_L for different dispersion methods, considering the influences of breakup rate and transformation of the interface shape on the dispersion process. Three models were developed to predict the dispersion size for different dispersion methods, and calculated data were in good agreement with the experimental results. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Interface‐tailored and nanoengineered polymeric materials for (opto)electronic devices

For plastic (opto)electronic devices such as light‐emitting diodes (LEDs), photovoltaic (PV) cells and field‐effect transistors (FETs), the processes of charge (hole/electron) injection, charge transport, charge recombination (exciton formation), charge separation (exciton diffusion and dissociation) and charge collection are critical to enhance their performance. Most of these processes are relevant to nanoscale and interfacial phenomena. In this review, we highlight the state‐of‐the‐art developments of interface‐tailored and nanoengineered polymeric materials to optimize the performance of (opto)electronic devices. These include (1) interfacial engineering of anode and cathode for polymer LEDs; (2) nanoengineered (C₆₀ and inorganic semiconductor nanoparticles) π‐conjugated polymeric materials for PV cells; and (3) polymer and monolayer dielectrics/interfaces for FETs and light‐emitting and nano‐FETs. Copyright © 2009 Society of Chemical Industry     

Rice‐husk‐ash‐based silica as a filler for embedding composites in electronic devices

We carried out a feasibility study of the use of black rice husk ash (RHA) as a filler in epoxy resin for embedding material in electrical and electronic applications. We made a comparison by mixing RHA and two commercial fillers, fused and crystalline silica, with epoxy resin at weight fractions ranging from 20–60%. RHA‐filled epoxy resin had higher mixing viscosity, coefficient of thermal expansion, and water absorption percentage than commercial‐silica‐filled epoxy composite. However, the impact strength of all composites was comparable, but the tensile strength and elongation at break of silica‐filled epoxy were slightly superior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3013–3020, 2002     

pH‐sensitive keratin‐based polymer hydrogel and its controllable drug‐release behavior

Using feather keratin as biocompatible and inexpensive natural biopolymer and methacrylic acid as a functional monomer, we prepared a pH‐sensitive feather‐keratin‐based polymer hydrogel (FKPGel) with grafted copolymerization. The obtained FKPGel was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The swelling behavior and pH sensitivity of the FKPGel were investigated. When the small molecule (rhodamine B) and macromolecule (bovine serum albumin) were used as model drug molecules, the FKPGel exhibited controllable release behavior in vitro, and the hydrogels had pH sensitivity. For a small molecular drug, the cumulative release rate was 97% in 24 h at pH 8.4. For macromolecular drug, the cumulative release rate reached 89% at pH 7.4. Its release behavior could be controlled by the pH value. In summary, a simple method was found to reuse disused feathers. It is a kind of pH‐sensitive hydrogels to be applied in drug‐delivery systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41572.     

Carbazole‐based electroluminescent devices obtained by vacuum evaporation

Transparent conductive oxide (SnO₂)/organic layers/aluminum thin film sandwich structures were obtained by vacuum evaporation. The organic component was either a thin carbazole film or a bilayer. In that case, the carbazole film was deposited onto a thin insulating polymer film. The polymer used was the poly(tetrabromo‐p‐phenyleneselenide) (PBrPDSe). Photoluminescence measurements have shown that the carbazole thin films emit blue light. (I‐V) measurements have shown that the structures exhibit diode characteristics. The forward direction is obtained when the transparent conductive oxide (TCO) is positively biased. However, the reproducibility of the results obtained with a single carbazole layer is poor. It appears that the stability of the sample is improved when a thin PBrPDSe film (40 nm) is introduced between the carbazole and the SnO₂. The polymer film avoids the short circuit effect. In that case, the turn‐on voltage of the diode is about 3 V, when the thickness of the carbazole film is around 250 nm and the electroluminescence appears at a voltage of about 5 V. It is shown that the thermionic effect cannot be used to explain the I‐V characteristics, which are interpreted with the help of the Fowler–Nordheim tunnel effect. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2042–2055, 2001     

Synthesis and degradation of sorbitol‐based polymers

A new class of biodegradable copolyesters was synthesized by the catalyst‐free melt condensation of sorbitol with citric acid, tartaric acid, and sebacic acid. The resulting polymers were designated as poly(sorbitol citric sebacate) [p(SCS)] and poly(sorbitol tartaric sebacate) [p(STS)]. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and differential scanning calorimetry analysis. Porous spongelike scaffolds were prepared with a salt‐leaching technique and characterized with scanning electron microscopy. Tensile testing of the p(SCS) and p(STS) polymers showed that they exhibited a wide range of mechanical properties. The Young's modulus and tensile strengths of the polymers ranged from 1.06 ± 0.12 to 462.65 ± 34.21 MPa and from 0.45 ± 0.04 to 20.32 ± 2.54 MPa, respectively. In vitro degradation studies were performed on disc‐shaped polymer samples. The half‐life of the polymers ranged from 0.54 to 38.52 days. The percentage hydration of the polymers was in the range 9.36 ± 1.26 to 78.25 ± 1.91, with sol contents of 2–14%. At any given polymer composition, the Young's modulus and tensile strength of p(SCS) was higher than that of p(STS), whereas the degradation rates of p(SCS) was lower than that of p(STS). This was attributed to the structural difference between the citric and tartaric monomers and to the degree of crosslinking. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Lecithin‐acrylamido‐2‐methylpropane sulfonate based crosslinked phospholipid nanoparticles as drug carrier

In this study, a novel paclitaxel (PTX) loaded and a crosslinked solid phospholipid nanoparticles (SLN‐PTX) with negative surface charge was prepared by UV polymerization for drug delivery. Capping of positive charge of zwitterionic lecithin with negative charge of sodium 2‐acrylamido‐2‐methyl‐1‐propanesulfonate (AMPS‐Na) through cation exchange interaction produced a lecithin‐AMPS (L‐AMPS) complex. The amphiphilic and negative charged lipid complex was emulsified in the presence of emulsifier, paclitaxel, initiator, and methacrylated poly ε‐caprolacton‐diol (PCL‐MAC) as a spacer. The colloidal system was subjected to UV‐irradiation to obtain crosslinked nanoparticles. Completion of the UV‐polymerization was monitored with differential scanning calorimetry (DSC), which indicated the disappearance of exothermic peaks of vinyl groups. The nanoparticle system, having an average size of 200 nm, exhibited high drug encapsulation (96%) with negatively charged surface (zeta potential had an average of ?70 mV). PTX release profiles of the crosslinked and uncrosslinked SLN‐PTXs were studied and their pharmacological properties were compared. The crosslinked nanoparticles exhibited more controlled release behavior with longer release time compared to the uncrosslinked ones. In vitro cytotoxicity test was conducted on MCF‐7 human breast adenocarcinoma cell line, which indicated that the crosslinked SLN‐PTXs have a potential therapeutic effect for breast cancer treatments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44105.     

Tung oil‐based thermosetting polymers for self‐healing applications

Several bio‐renewable thermosetting polymers were successfully prepared from tung oil through cationic polymerization for the use as the healing agent in self‐healing microencapsulated applications. The tung oil triglyceride was blended with its methyl ester, which was produced by saponification followed by esterification. The changes in storage modulus, loss modulus, and glass transition temperature as functions of the methyl ester content were measured using dynamic mechanical analysis. In addition, the fraction of cross‐linked material in the polymer was calculated by Soxhlet extraction, while proton nuclear magnetic resonance, Fourier transform infrared spectroscopy and TEM were used to investigate the structure of the copolymer networks. The thermal stability of the thermosets as a function of their methyl ester blend contents was determined by thermogravimetric analysis. Finally, the adhesive properties of the thermosets were studied using compressive lap shear and the fracture surfaces were analyzed using SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40406.     

Stretchable and self-healing polymers and devices for electronic skin

This review covers some of the most recent advances in stretchable and self-healing polymers and devices for Electronic skin (E-skin) applications. Applications for both stretchable and self-healing materials include, but are not limited to, electronics, displays, energy, the environment, and medicine. While the majority of organic materials can generally be rendered flexible, such materials are not stretchable, which is a key mechanical property necessary to realize applications of E-skin for prosthetics, artificial intelligence, systems for robotics, personal health monitoring, biocompatibility, and communication devices. In our effort to survey materials utilized in various components of an electronic device, we report herein recent advances in stretchable and self-healing conductors, semiconductors, and substrates. We highlight some key technologies recently developed in stretchable organic-based sensors, solar cells, light-emitting diodes, and self-healing electronic devices.