Preparation and characterization of organosoluble copolyimides based on a pair of commercial aromatic dianhydride and one aromatic diamine, 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene,series

A series of copolyimides (co‐PIs) with high molecular weights, excellent mechanical properties, heat‐resistant properties, and good solubilities in organic solvents were synthesized from six kinds of commercial dianhydrides (IIa–f) and 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene (I). Monomers (IIa–d) for synthesizing insoluble PIs and monomers (IIe,f) for synthesizing soluble PIs were used to synthesize co‐PIs with arbitrary solubilities. Nine kinds of soluble co‐PIs (IIIa–e and IVa–d) were synthesized through chemical or thermal cyclodehydration. These co‐PIs were found to be easily soluble as well as able to be processed by casting from their solutions such as NMP, DMAc, m‐cresol, pyridine, THF, and CH₂Cl₂. The easily dissolved characteristics of this series of co‐PIs stemmed from the t‐butyl group and ether group within I. Besides, when the used dianhydride molecules contained the organosoluble groups, the solubilities in organic solvents could be greatly enhanced. The co‐PIs could improve the processability of polymers, while increasing their flexible mechanical properties and maintaining their excellent heat‐resistant properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 87–95, 2000     

Surface and Interfacial Studies of Plasma-Modified Composite Surfaces

Model epoxy and bismaleimide compounds in thin film form were used to simulate epoxy and bismaleimide composite surfaces, in order to study compositional changes and interfacial reactions induced by oxygen plasma treatment. X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IR-RAS) were used to probe chemical changes which occurred. XPS and IR-RAS were found to be complementary techniques in determining the nature of functional groups incorporated into surfaces by plasma treatment. IR-RAS analysis of the model surfaces following exposure to a liquid epoxy resin revealed that while adsorption of the liquid epoxy occurred on both plasma-treated and nonplasma-treated surfaces, the oxygen plasma-treated surface alone was capable of initiating ring-opening reactions in the epoxy. However, this effect was not observed unless immediate contact was made between the plasma-treated surface and the liquid epoxy resin, illustrating the short-lived reactivity of the functional groups on the plasma-treated surface.     

Pr3+/Er3+ Codoped Ge-As-Ga-S Glasses as Dual-Wavelength Fiber-optic Amplifiers for 1.31 and 1.55 μm Windows

Fluorescence emissions at both 1.31 and 1.55 μm communication windows were observed from Pr³⁺/Er³⁺ codoped Ge-As-Ga-S glasses with a single wavelength pumping at 986 nm. The lifetime of the Er³⁺:⁴ I _11/2 level decreased as the Pr³⁺ concentration increased, and that of the Pr³⁺:¹ G ₄ level increased as the Er³⁺ concentration increased. Energy transfer from the Er³⁺:⁴ I _11/2 level to the Pr³⁺:¹ G ₄ level was responsible for emission of the 1.31 μm fluorescence from the Pr³⁺:¹ G ₄ level. Ge-As-Ga-S glasses that have been doped with Pr³⁺ and Er³⁺ cations are promising amplifier materials for both 1.31 and 1.55 μm communication windows.     

Reactive compatibilization of the poly(ethylene terephthalate)/liquid crystalline polymer blends by solid epoxy resin as a coupling agent

A selected reactive coupling agent can be served as an effective compatibilizer for certain immiscible and incompatible blends should both blend constituents possess the necessary functional groups that can react with the coupling agent at comparable rates. Solid epoxy resin with two epoxide endgroups per molecule was demonstrated to be an efficient reactive compatibilizer for the incompatible blends of poly(ethylene terephthalate) (PET) and copolyester liquid crystalline polymer (LCP) by functioning as a coupling agent. The main chain structure of the epoxy resin is neither identical not miscible with PET and LCP and tends to reside at interface during melt mixing. This preferential residence gives the epoxy compatibilizer greater opportunity to react with both PET and LCP simultaneously to produce the in situ–formed epoxy-b-LCP mixed copolymer. This in situ–formed mixed copolymer is highly effective in compatibilizing the PET/LCP blends. This reactive epoxy compatibilizer enhances the LCP fibril formation and results in substantial improvements on stiffness and toughness of the PET/LCP blends. © 1996 John Wiley & Sons, Inc.