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951.
952.
Chien‐Chung Han Ku‐Feng Yang Shih‐Ping Hong Arumugam Balasubramanian Yi‐Te Lee 《Journal of polymer science. Part A, Polymer chemistry》2005,43(9):1767-1777
New highly solution‐processable aniline/butylthioaniline copolymers were prepared via oxidative copolymerization (OCP) and by concurrent reduction and substitution (CRS). Butylthio‐substituted polyaniline obtained via the CRS route (Pan‐SBu), being in line with the expected property changes after the addition of an electron‐donating substituent to an aromatic ring, displayed a lowered redox potential (E0) and a redshifted maximum wavelength (λmax; ultraviolet–visible) in comparison with its parent unsubstituted polyaniline (Pan). However, copolymers CP1–CP4 (obtained via the OCP method) displayed opposite behaviors, showing higher E0 values and blueshifts in λmax than the unsubstituted Pan. The results suggested that CP1–CP4 had shorter conjugation lengths than the unsubstituted Pan, possibly because of their chain conjugation defects (e.g., 1,3‐ring linkage structures), as evidenced by IR studies. The results of 1H NMR studies also indicated that Pan‐SBu had much higher structural homogeneity than copolymer CP4. Because the CRS synthetic route involved no backbone alternations, the resultant copolymer (Pan‐SBu) should have maintained the same backbone structure and hence the high conductivity of the parent unsubstituted Pan. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1767–1777, 2005 相似文献
953.
Yeng‐Fong Shih 《Journal of Polymer Science.Polymer Physics》2009,47(13):1231-1239
In this study, carbon nanotubes (CNTs) were first modified using N,N′‐ dicyclohexylcarbodiimide (DCC) dehydrating agents. Subsequently, the poly(butylene succinate)/multiwalled carbon nanotube (PBS/MWNTs) nanocomposites were prepared through facile melt blending. Thermal degradation of these PBS/MWNT nanocomposites was investigated; the kinetic parameters of degradation were calculated using the Coats and Redfern, Ozawa, and Horowitz and Metzger methods, respectively. It was found that the degradation reaction mechanism of PBS and the CNT‐C18 containing nanocomposites at lower temperature was likely to produce an F1 model through reaction of random chain cleavage (cis‐elimination). However, the reaction mechanism at higher temperature was likely to be a D1 model because of the dominant diffusion control effect. Moreover, it was found that the activation energies of CNT‐C18‐containing PBS nanocomposites were first increased with the content of CNT‐C18, but then decreased after the content was larger than 0.5 wt % for all models at differing heating rates. This may be due to the formation of a conductive network of CNTs in the polymer matrix at higher content of CNTs, which lead to better heat and electrical conductivity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1231–1239, 2009 相似文献
954.
Chen‐Han Chien Ping‐I Shih Ching‐Fong Shu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2938-2946
We have developed efficient white‐light‐emitting polymers through the incorporation of low‐bandgap orange‐light‐emitting benzoselenadiazole ( BSeD ) moieties into the backbone of a blue‐light‐emitting bipolar polyfluorene (PF) copolymer, which contains hole‐transporting triphenylamine and electron‐transporting oxadiazole pendent groups. By carefully controlling the concentrations of the low‐energy‐emitting species in the resulting copolymers, partial energy transfer from the blue‐fluorescent PF backbone to the orange‐fluorescent segments led to a single polymer emitting white light and exhibiting two balanced blue and orange emissions simultaneously. Efficient polymer light‐emitting devices prepared using this copolymer exhibited luminance efficiencies as high as 4.1 cd/A with color coordinates (0.30, 0.36) located in the white‐light region. Moreover, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study revealed that energy transfer from the PF backbone to the low‐bandgap segments, rather than charge trapping, was the main operating process involved in the electroluminescence process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2938–2946, 2007 相似文献
955.
We use the three-dimensional finite-difference time-domain method to investigate surface plasmon polariton coupling between
two nano-recording marks which are of different shapes. The different coupling characteristics and the influence of these
coupling effects on the read-out reflection signal will be discussed. 相似文献
956.
The paper describes a wet process for modifying the surface of polydimethylsiloxane (PDMS) using H2SO4/HNO3 solutions. The oxidation on the surface of PDMS was confirmed by the examinations of Fourier transform infrared spectrometry (FTIR), contact angle of water drop and X-ray photoelectron spectroscopy (XPS). The hydrophobic surface of pristine PDMS was not only changed to hydrophilic, but also formed wrinkles on it after chemical modification. Bilayer systems, stiff oxidized PDMS layers were capped on soft PDMS foundations, would generate easily compressive stresses due to the large difference in volumetric contraction rates and led to form wrinkles on the surface. Experimental results demonstrated the periodicity of wrinkles was controllable by controlling the duration of oxidation. Therefore, wrinkles could be arranged orderly by the guidance of external forces before oxidization. The potential technology for generating and ordering wrinkles on the PDMS surface is valuable in the applications of pressure sensors, biology, micro-optics and nano-/micro-fabrication in the future. 相似文献
957.
Hsu-Wei Fang Meng-Lin Shih Huei-Ting Huang Hsuan-Liang Liu Charng-Bin Yang 《Applied Surface Science》2007,253(16):6896-6904
Under the articulation of artificial joints, ultra-high molecular weight polyethylene (UHMWPE) acts as a bearing surface under the lubrication of synovial fluid containing various proteins. Albumin is the most abundant composition and acts as the interfacial molecule in the boundary lubrication regime. The dissipated energy including thermal energy from the tribological process may lead to the conformational change of albumin molecules.In this study, a series of experiments were designed and carried out to investigate the association of thermal unfolding albumin and the frictional characteristics of highly-crosslinked UHMWPE (x-UHMWPE). An accelerated oxidation experiment was used to prepare x-UHMWPE with an oxidized surface. Analysis of the albumin protein by circular dichroism (CD) spectroscopy was performed to detect the conformational changes during a thermal process. In addition, a molecular simulation was performed to understand the structural change of albumin at various temperatures and the exposed hydrophobic contact areas. Linear reciprocating frictional tests were carried out to obtain the start-up friction coefficients. The results indicate that a decrease of α-helix content and an unfolding of the secondary structure of albumin were observed with increasing temperatures which may come from the frictional heat of joint articulation process. The conformational change of albumin differentiates the frictional characteristics for x-UHMWPE with different oxidation levels. A model, describing that the properties of the lubricating molecules and articulating surfaces may affect the adsorption of the boundary lubrication thin film which is critical to the tribological behavior, is proposed. 相似文献
958.
Jyh‐Myng Zen Ting‐Hao Yang Annamalai Senthil Kumar Yu‐Ju Chen Jaw‐Cherng Hsu Ying Shih 《Electroanalysis》2009,21(20):2272-2276
Aluminum chlorohydrate (Al2(OH)5Cl?2H2O, ACH) is an active ingredient in many antiperspirants and deodorants formulation to reduce the body odors (mainly sweat) through interaction with apocrine sweat glands to produce insoluble aluminum hydroxide and free chloride, which then plugs the sweat gland that stops the flow of sweat to the skin's surface. We demonstrated here an one drop (50 μL) electrochemical sensing of the ACH using an in‐built three screen‐printed electrodes assembly containing Ag as working and pseudo reference and carbon as counter electrode system (AgSPE). The free Cl? ion librated from ACH/H2O reaction was detected at AgSPE surface at 0.072 V vs. pseudo Ag reference electrode system in pH 2 phosphate solution by Cyclic voltammetric Technique. Under optimal working condition the AgSPE shows a linear calibration plot in the window of 30–2000 ppm of ACH with sensitivity and regression values of 0.104 μA/ppm and 0.998 respectively. Calculated detection limit is 3.03 ppm. RSD values of intra‐ and interassays were 0.19% and 2.79% respectively. Finally, real sample (antiperspirant deodorant lotions) assays were successfully demonstrated with results comparable to the predicted values. 相似文献
959.
C. R. Mendonca M. Kandyla T. Shih R. F. Aroca C. J. L. Constantino E. Mazur 《Applied Physics A: Materials Science & Processing》2009,96(2):369-372
We report a pump-probe study of the two-photon induced reflectivity changes in bis (n-butylimido) perylene thin films. To enhance the two-photon excitation we deposited bis (n-butylimido) perylene films on top of gold nanoislands. The observed transient response in the reflectivity spectrum of bis
(n-butylimido) perylene is due to a depletion of the molecule’s ground state and excited state absorption. 相似文献
960.
T. Shih M. T. Winkler T. Voss E. Mazur 《Applied Physics A: Materials Science & Processing》2009,96(2):363-367
Using a broad band dual-angle pump-probe reflectometry technique, we obtained the ultrafast dielectric function dynamics of
bulk ZnO under femtosecond laser excitation. We determined that multiphoton absorption of the 800-nm femtosecond laser excitation
creates a large population of excited carriers with excess energy. Screening of the Coulomb interaction by the excited free
carriers causes damping of the exciton resonance and renormalization of the band gap causing broadband (2.3–3.5 eV) changes
in the dielectric function of ZnO. From the dielectric function, many transient material properties, such as the index of
refraction of ZnO under excitation, can be determined to optimize ZnO-based devices. 相似文献