Facile synthesis of high‐performance poly(pyrrolone imide)s from an unsymmetric phosphinated triamine

High‐performance and flexible poly(pyrrolone imide)s (PPyIs) were firstly prepared by the reaction of dianhydrides with an unsymmetric phosphinated triamine, 1‐(3,4‐diaminophenyl)‐1‐(4‐aminophenyl)‐1‐(6‐oxido‐6H ‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (1), which was prepared by a facile, one‐pot procedure from the reaction DOPO, 4‐aminoacetophenone in excess o‐phenylenediamine in the presence of p‐toluenesulfonic acid. Thermal properties of the resulting PPyIs were evaluated and compared with those of phosphinated polyimides with a similar structure. All of the prepared PPyIs films are tough and creasable. They display higher T_g (374–412 °C), lower coefficient of thermal expansion (34–46 ppm/°C), and better thermal stability (T_d 5 wt %: 456–477 °C, 800 °C char yield: 59–63%) than analogous phosphinated polyimides. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2709–2715     

Practical issues for two-light-sources model of phosphor-based white light-emitting diode

We report an intuitive approach to simulating the performance of the phosphor-based light emitting diode (LED) by using the two-light-sources model for an optimized LED lens. The optimized secondary lens shape is achieved by approaching a uniform energy distribution on the detecting plane. Both the spectrum and spatial apodization of the LED structure are discussed, and the results indicate that the two-light-sources model can solve the misleading design on the phosphor-based LED due to imperfect color mixing of light source, that one can satisfy the highly uniformity requirement for specific applications, such as display backlight or optogenetic.     

Effects of Cr doping on physical properties of amorphous In-Ga-Zn-O films

Amorphous thin films of InGaZnO₄ (a-IGZO) doped with Cr have been fabricated by using pulsed-laser deposition (PLD). The electrical, optical and magnetic properties of Cr-doped a-IGZO films grown at 25 °C and 150 °C were investigated. The conductivity, optical transmission and band gap of films are remarkably enhanced by increasing the growth temperature. Conductivity, carrier concentration and mobility decrease with increasing the Cr content. However, the optical transmission and band gap are not significantly affected by Cr doping. Moreover, all Cr-doped films exhibit room-temperature ferromagnetism.     

Closed-form recursive formula for an optimal tracker with terminal constraints

Feedback control laws are derived for a class of optimal finite time tracking problems with terminal constraints. Analytical solutions are obtained for the feedback gain and the closed-loop response trajectory. Such formulations are expressed in recursive forms so that a real-time computer implementation becomes feasible. An example involving the feedback slewing of a flexible spacecraft is given to illustrate the validity and usefulness of the formulations.     

Adsorption of basic dyes onto montmorillonite

Ca-montmorillonite (Ca-Mont) was exchanged with titanium cations and the adsorption equilibrium and kinetics of Basic Green 5 (BG5) and Basic Violet 10 (BV10) on these montmorillonites were measured to examine the ion-exchange effects on the basic dyes adsorption. The relationship between the dye adsorption and the alteration of pore structures of montmorillonite induced by ion-exchange processes was discussed. Moreover, the changes in the surface and pore structure of montmorillonites during adsorption were characterized based on classical and fractal analyses of the nitrogen adsorption isotherms as well as the XRD patterns. The decrease in BET surface area of montmorillonites after adsorption of dyes was interpreted in terms of both the coverage of some surface roughness (surface screening effect) and the inhibition of the movement of nitrogen molecule into some pores (pore blocking effect). The surface fractal dimension D was used to examine whether or not the surface screening effect exists and the pore blocking effect was examined with the changes of mean pore size before and after adsorbing basic dyes.     

Synthesis of thermosetting polyetherimide‐containing allyl groups

An allyl‐containing diphenol, 1‐(3‐allyl‐4‐hydroxyphenyl)‐1‐(4‐hydoxyphenyl)‐1‐(6‐oxido‐6H ‐dibenz[c,e][1,2]oxaphosphorin‐6‐yl)ethane (1) , was prepared from a one‐pot reaction of 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide, 4‐hydroxyacetophenone, and 2‐allylphenol in the presence of p‐toluenesulfonic acid monohydrate. Then, an allyl‐containing dietheramine, 1‐(4‐(4‐aminophenoxy)phenyl)‐1‐(3‐allyl 4‐(4‐aminophenoxy)‐phenyl)‐1‐(6‐oxido‐6H‐dibenz[c,e][1,2] oxaphosphorin‐6‐yl)ethane (3) , was prepared from the nucleophilic substitution of (1) with 4‐fluoronitrobenzene, followed by the reduction of the dinitro groups by Fe/HCl. A flexible polyetherimide (PEI) (4) with a curable characteristic was prepared from the condensation of (3) and 4,4′‐oxydiphthalic anhydride (ODPA) in m‐cresol in the presence of isoquinoline. Curing PEI (4) at 300 °C leads to PEI (5) , which exhibits much a higher T_g value (307 °C) and a lower coefficient of thermal expansion (CTE) (29 ppm/°C) than PEI (4) (T_g = 253 °C, CTE 52 ppm/°C). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Ultraviolet-assisted synthesis of organic/inorganic hybrid nanocomposites and their application for lifetime enhancement of light emitting diodes

Ultraviolet (UV) curable organic/inorganic hybrid nanocomposites with excellent gas barrier effect, good adhesion strength, high refractive indices, moderate hardness, and fast curing speed have been successfully quickly synthesized by UV irradiation and utilized for the encapsulation of light emitting diodes (LEDs). In addition, the experimental results reveal that lab-made nanocomposites effectively resist the penetration of oxygen and moisture in the air into the LEDs and thus enhance their lifetimes to achieve 18,300 h while those without encapsulation are only 2400 h.     

Berkovich nanoindentation and deformation mechanisms in GaN thin films

The deformation mechanisms of GaN thin films obtained by metal-organic chemical vapor deposition (MOCVD) method were studied using nanoindentation with a Berkovich diamond indenter, micro-Raman spectroscopy and the cross-sectional transmission electron microscopy (XTEM) techniques. Due to the sharpness of the tip of Berkovich indenter, the nanoindentation-induced deformation behaviors can be investigated at relatively lower load and, hence, may cover wider range of deformation-related phenomena over the same loading range. The load-displacement curves show the multiple “pop-ins” during nanoindentation loading. No evidence of nanoindentation-induced phase transformation and cracking patterns were found up to the maximum load of 300 mN, as revealed from the micro-Raman spectra and the scanning electron microscopy (SEM) observations within the mechanically deformed regions. In addition, XTEM observation performed near the cross-section of the indented area revealed that the primary deformation mechanism in GaN thin film is via propagation of dislocations on both basal and pyramidal planes. The continuous stiffness measurement (CSM) technique was used to determine the hardness and Young's modulus of GaN thin films. In addition, analysis of the load-displacement data reveals that the values of hardness and Young's modulus of GaN thin films are 19 ± 1 and 286 ± 25 GPa, respectively.