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51.
Der-Jang Liaw Been-Yang Liaw Kuo-Liang Su 《Journal of polymer science. Part A, Polymer chemistry》1999,37(13):1997-2003
A series of new soluble polyamides having isopropylidene and methyl-substituted arylene ether moieties in the polymer chain were prepared by the direct polycondensation of 3,3′,5,5′-tetramethyl-2,2-bis[4-(4-carboxyphenoxy)phenyl]propane and various diamines in N-methyl-2-pyrrolidinone (NMP) containing CaCl2 using triphenyl phosphite and pyridine as condensing agents. Polymers were produced with moderate to high inherent viscosities of 0.85–1.47 dL g−1 while the weight-average molecular weight and number-average molecular weight were in the range of 86,700–259,000 and 43,300–119,000, respectively. All the polymers were readily dissolved in polar aprotic solvents such as NMP, N,N-dimethylacetamide, and N,N-dimethylformamide, as well as less polar solvents such as m-cresol and pyridine, and even soluble in tetrahydrofuran. These polymers were solution-cast into transparent, flexible and tough films. All of the polymers were amorphous and the polyamide films had a tensile strength range of 82–122 MPa, an elongation at break range of 6–18%, and a tensile modulus range of 2.0–2.8 GPa. These polyamides had glass transition temperatures between 233–260°C and 10% weight loss temperatures in the range of 450–489 and 459–493°C in nitrogen and air atmosphere, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1997–2003, 1999 相似文献
52.
Der-Jang Liaw Been-Yang Liaw Jeng-Ming Tseng 《Journal of polymer science. Part A, Polymer chemistry》1999,37(14):2629-2635
A series of novel soluble poly(amide-imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl]hexafluoropropane, with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl2 using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.78–1.63 dL g−1. The polymers were amorphous and readily soluble in aprotic polar solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide as well as in less polar solvents such as pyridine and γ-butyrolactone, and also in tetrahydrofuran. The polymer films had tensile strength of 84–129 MPa, an elongation at break range of 6–22%, and a tensile modulus range of 2.0–2.7 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 240–282°C. These polymers were fairly stable up to a temperature around or above 400°C, and lose 10% weight in the range of 450–514°C and 440–506°C in nitrogen and air, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2629–2635, 1999 相似文献
53.
Der-Jang Liaw Been-Yang Liaw Chao-Yi Chung 《Journal of polymer science. Part A, Polymer chemistry》1999,37(15):2815-2821
A new cardo diamine monomer, 5,5-bis[4-(4-aminophenoxy)phenyl]-4,7-methanohexahydroindane (II), was prepared in two steps with high yield. The monomer was reacted with six different aromatic tetracarboxylic dianhydrides in N,N-dimethylacetamide (DMAc) to obtain the corresponding cardo polyimides via the poly(amic acid) precursors and thermal or chemical imidization. All the poly(amic acid)s could be cast from their DMAc solutions and thermally converted into transparent, flexible, and tough polyimide films which were further characterized by x-ray and mechanical analysis. All of the polymers were amorphous and the polyimide films had a tensile strength range of 89–123 MPa, an elongation at break range of 6–10%, and a tensile modulus range of 1.9–2.5 GPa. Polymers Vc, Ve, and Vf exhibited good solubility in a variety of solvents such as N-methyl-2-pyrrolidinone (NMP), DMAc, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, γ-butyrolactone, and even in tetrahydrofuran and chloroform. These polyimides showed glass-transition temperatures between 274 and 299°C and decomposition temperatures at 10% mass loss temperatures ranging from 490 to 521°C and 499 to 532°C in nitrogen and air atmospheres, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2815–2821, 1999 相似文献
54.
This paper reports the effect of water vapour on particulate matter (PM) during the separate combustion of in situ volatiles and char generated from chromated-copper-arsenate-treated (CCAT) wood at 1300 °C. Combustion of in situ volatiles produces only PM with aerodynamic diameter?<1?µm (i.e., PM1), dominantly PM with aerodynamic diameter?<0.1?µm (i.e., PM0.1). Water vapour could significantly enhance the nucleation, coagulation and condensation of fine particles and reduce the capture of Na and K by the alumina reactor tube via reduced formation of alkali aluminates, leading to increases in both yield and modal diameter of PM0.1. Water vapour could also enhance char fragmentation hence increase the yield of PM with aerodynamic diameter between 1 and 10?µm (i.e., PM1–10) during char combustion. For trace elements, during in situ volatiles combustion, volatile elements (As, Cr, Ni, Cu and Pb) are only presented in PM1 and water vapour alters the particle size distributions (PSDs) but has little effect on the yields of these trace elements. During char combustion, As, Cr, Cu and Ni are present in both PM1 and PM1–10 while the non-volatile Mn and Ti are only present in PM1–10. Increasing water vapour content increases the yields of As, Cr, Cu, Ni, Mn and Ti in PM1-10 due to enhanced char fragmentation. During char combustion, water vapour also originates less oxidising conditions locally for enhancing As release, promotes the generation of gaseous chromium oxyhydroxides and inhabits the production of NiCl2 (g), leading to increased yields of As and Cr and decreased yield of Ni in PM0.1. 相似文献
55.
A. Povolotskiy T. Ivanova A. Manshina Y. Tver’yanovich Shien-Kuei Liaw Chu-Lin Chang 《Applied Physics A: Materials Science & Processing》2009,96(4):887-891
Er3+ clustering phenomenon in Ga–Ge–S chalcogenide system is studied using Raman spectroscopy. The Raman spectra from 10 to 500
cm−1 for glasses (100−y)[15Ga2S3–85GeS2]–yEr2S3 (y=0.08−5.00 mol. %) have been analyzed. To reveal the influence of the chemical composition on the glass structure the intensity
of the peak corresponding to Ge–Ge (Ga–Ga) homopolar bonds has been examined. The peak intensity increase with Er2S3 concentration change in the region 0<C(Er2S3)<2 mol. % has been interpreted in terms of the sulphur deficiency in the glass resulting in the formation of S3Ge–GeS3 (S3Ga-GaS3) structural units. The further increase in concentration beyond 2 mol. % reduces the sulphur deficiency, which can be attributed
to the formation of the ternary compound Er3GaS6. The structural units Er3GaS6 contain a large mol. fraction of Er3+ or, in other words, Er3+ clusters. The data obtained from the low-frequency Raman spectra (boson band) indicate strong variations of the medium-range
order (MRO) in the glasses induced by Er3+. The observed behavior of the MRO size (the correlation length) with increasing of Er2S3 concentration provides for additional evidence of the Er3+ clustering. 相似文献
56.
Abstract Stress intensity factors are evaluated for a singly or doubly cracked fastener hole with frictional traction in an anisotropic plate, using a special kernel boundary integral equation (BIE) approach. The integration kernel (Green's function) used in this BIE approach has already taken the presence of the crack (or cracks) into account, thus.avoiding the need for element discretization to model the stress singularity at the crack tip. The Green's function employed is that of an infinite anisotropic plate containing an elliptical hole or crack, and subjected to an arbitrarily positioned point force. Several types of normal and shear traction conditions at the pinhole interface are considered. Numerical results are obtained for various geometrical and loading conditions and are compared with known solutions, where available, for their isotropic counterparts. 相似文献
57.
58.
Wan-Fu LienPo-Chen Huang Shi-Chang TsengChia-Hsiang Cheng Shih-Ming LaiWen-Chang Liaw 《Applied Surface Science》2012,258(7):2246-2254
Tetraethoxy silane was used to functionalize the surface of fiber glass (FG) for adsorption with the electroless plated silver shell. The performance of electroless silver plated FG with tetraethoxy silane modification was compared to that of unmodified FG in terms of mechanical and electrical properties. The silane bridge provided more stability for binding with different concentrations of electroless plating silver ions. The characterization was investigated by using field emission scanning electron microscope (FESEM), X-ray diffraction patterns (XRD), energy-dispersion X-ray (EDX), metal microscope (MM) and electric resistance. The Ag coating on TEOS modified FG was more durable than that of unmodified FG in the ball milling test, as confirmed by the data of electric resistance and residue weight. The optimized conditions for producing the Ag coating FG were also investigated. The Ag-Si-FG-3-c product in this study has the lowest electrical resistance of 1.56 × 103 Ω/cm2 and good mechanical stability as exhibited in ball milling tests. 相似文献
59.
Huang HC Chiou CT Hsiao PC Liaw CC Zhang LJ Chang CL Chen IS Chen WC Lee KH Kuo YH 《Molecules (Basel, Switzerland)》2012,17(2):1837-1851
One new phenylpropanoid, turformosin A (1), and one new triterpene, turformosinic acid (2), together with 16 known compounds, were isolated from the stems of Turpinia formosana Nakai. All structures were elucidated on the basis of spectroscopic analysis, including 1D- and 2D-NMR techniques and MS analysis. Selected isolated compounds were evaluated for in vitro cytotoxicity against four human cancer cell lines and antioxidant scavenging effects on DPPH. (-)-(7'S,8'S)-threo-carolignan X (3) exhibited cytotoxicity against Hep2, WiDr, Daoy, and MCF-7 cell lines with ED(50) values of 3.60, 4.45, 6.07, and 13.7 μg/mL, respectively. Turformosin A (1), (-)-(7'S,8'S)- threo-carolignan X (3), methoxyhydroquinone-4-β-D-glucopyranoside (5), and methoxy-hydroquinone-1-β-D-glucopyranoside (6), exhibited similar anti-oxidative activity. Hep2 cells treated with 10 μg/mL of 3 showed elevation of sub-G1 population (from 20% at 8 h to 60% at 48 h), and activation of caspase-9/caspase-3/PARP cascade. Compound 3 induced intrinsic apoptotic pathway in Hep2 cells with dose and time dependence (10 μg/mL for 8 h). 相似文献
60.
Hui-Yu Fang Chih-Chuang Liaw Chih-Hua ChaoZhi-Hong Wen Yang-Chang WuChi-Hsin Hsu Chang-Feng DaiJyh-Horng Sheu 《Tetrahedron》2012,68(47):9694-9700
Nine new steroids, sclerosteroids A-I (1, 5, 6, 8-13), along with 18 known metabolites (2-4, 7, 14-27), were isolated from the soft coral Scleronephthya gracillimum. These structures were elucidated on the basis of detailed spectroscopic analysis. The absolute configurations of sugar moieties in steroidal glycosides 10-13 were determined by HPLC analysis of the o-tolylthiocarbamate derivatives of the liberated sugars from hydrolysis of these steroidal giycosides. Cytotoxic and anti-inflammatory activities of these compounds were measured in vitro. 相似文献