A new triphenylamine-containing diamine monomer, 4,4′-diamino-3′′,4′′-dimethyltriphenylamine (DADT), was successfully synthesized by the cesium fluoride-mediated condensation of 3,4dimethylaniline with 4-fluoronitrobenzene, followed by reduction. The monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce a series of novel polyamides and polyimides, respectively. A new triphenylamine-containing dicarboxylic acid monomer, 4,4′-trimellitimido-3′′,4′′-dimethyltriphenylamine (TDT), was successfully synthesized by refluxing the diamine, DADT, with trimellitic anhydride in glacial acetic anhydride. A series of new poly(amide-imide)s were prepared from TDT with various diamines by the direct polycondensation. The polymers were obtained in quantitative yields with inherent viscosities of 0.61-2.28 dL g -1 . Most of the polymers dissolved in N-methyl-2pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, pyridine, and cyclohexanone. These polymers, especially poly(amide-imide)s, showed high glass transition temperatures between 254 and 326 °C. These polymers were fairly stable up to a temperature around or above 400 °C and lost 10% weight in the range of 430-566 and 462-574 °C in nitrogen and air, respectively. These tough and flexible polymer films had a tensile strength of 82-145 MPa, an elongation at break of 5-11%, and a tensile modulus of 1.7-3.3 GPa. The UV-vis absorption spectra revealed that most of the polymers had absorption maxima around 303 nm. Cyclic voltammograms of the polyamides, polyimides, and poly-(amide-imide)s showed an oxidation wave with a peak around 0.9, 1.1, and 1.3 V, respectively.
A new bulky pendent bis(ether anhydride), 1,1‐bis[4‐(4‐dicarboxyphenoxy)phenyl]‐4‐phenylcyclohexane dianhydride, was prepared in three steps, starting from the nitrodisplacement of 1,1‐bis(4‐hydroxyphenyl)‐4‐phenylcyclohexane with 4‐nitrophthalonitrile to form bis(ether dinitrile), followed by alkaline hydrolysis of the bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). A series of new poly(ether imide)s were prepared from the bis(ether anhydride) with various diamines by a conventional two‐stage synthesis including polyaddition and subsequent chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.50–0.73 dL g−1. The gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 57,000 and 130,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility in comparison with the other polyimides derived from adamantane, norbornane, cyclododecane, and methanohexahydroindane and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. These polymers had glass‐transition temperatures of 226–255 °C. Most of the polymers could be dissolved in chloroform in as high as a 30 wt % concentration. Thermogravimetric analysis showed that all polymers were stable up to 450 °C, with 10% weight losses recorded from 458 to 497 °C in nitrogen. These transparent, tough, and flexible polymer films could be obtained by solution casting from DMAc solutions. These polymer films had tensile strengths of 79–103 MPa and tensile moduli of 1.5–2.1 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2066–2074, 2002
A new bis(ether anhydride), 3,3′,5,5′‐tetramethyl‐2,2‐bis[4‐(4‐dicarboxyphenoxy)phenyl]propane dianhydride (3), was prepared in three steps: the nitro displacement of 4‐nitrophthalonitrile with 2,2‐bis(4‐hydroxy‐3,5‐dimethylphenyl)propane, the alkaline hydrolysis of the intermediate bis(ether dinitrile), and the subsequent dehydration of the resulting bis(ether diacid). A series of new highly soluble poly(ether imide)s with tetramethyl and isopropylidene groups were prepared from the bis(ether anhydride) 3 with various diamines by a conventional two‐stage synthesis including polyaddition and chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.54–0.73 dL g−1. Gel permeation chromatography measurements revealed that the polymers had number‐average and weight‐average molecular weights of up to 54,000 and 124,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility and were readily dissolved in various solvents such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. Most of the polymers could be dissolved with chloroform concentrations as high as 30 wt %. These polymers had glass‐transition temperatures of 244–282 °C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight losses recorded above 463 °C in nitrogen. These transparent, tough, and flexible polymer films were obtained through solution casting from N,N‐dimethylacetamide solutions. These polymer films had tensile strengths of 81–102 MPa and tensile moduli of 1.8–2.0 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2556–2563, 2002
Hybrid scrambling technique is proposed for NROM-based ROMs in order to enhance the fabrication yield and reliability. Besides the traditional hardware redundancy techniques, fault masking features are also exploited to further improve the fabrication yield and reduce the amount of extra spare rows/columns. The hybrid scrambling technique basically consists of the row scrambling and the column scrambling techniques. Therefore, instead of scrambling a memory row/column, a logical memory cell can be scrambled into any of the logical memory cell address. This greatly improves the flexibility of scrambling. A hybrid scrambling control word is used for the control of the scrambling. Since the codes to be programmed into the NROM chips are known before programming, selecting a suitable code for programming a faulty NROM chip is helpful to further mask the faulty effects. Based on the proposed technique, possibilities of fault masking can be maximized. The proposed test and repair techniques can be easily incorporated into the ROM BIST architectures. According to experimental results, the fabrication yield can be improved significantly. Moreover, the incurred hardware overhead is almost negligible.
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