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131.
《Journal of Polymer Science.Polymer Physics》2018,56(10):778-785
In this work, collapse of poly(N‐isopropyl‐acrylamide) (pNIPAM) grafted on the surface of the optical fiber taper is probed by measuring fluorescence of rhodamine B solution at various temperatures. It is observed that the fluorescence intensity through the taper shows a nonlinear response to temperature. According to the optical model for the special designed taper, it is realized that the nonlinear response results from changing in effective refractive index of interfacial layer between taper and solution. Analysis on relationship between signal change and collapse process reveals a springback process during the collapse of pNIPAM chains. Such a novel phenomenon is further investigated on method for fluorescence measurement and molecular weight of the polymer. These results have not only revealed details of the collapse, but also establish a novel technique for study the collapse of thermal sensitive polymers on the surface. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 778–785 相似文献
132.
Zhiqin Peng Yoichiro Yoshida Sachiko Sukigara 《Journal of Polymer Science.Polymer Physics》2010,48(1):1-14
A novel macro/nano blended nonwoven with excellent physical properties was prepared by electrospinning polyurethane (PU) nanofibers onto the surface of ramie webs under different weight ratios of N,N‐dimethylacetamide (DMAc)/acetone cosolvents. The ratio of cosolvents has a significant influence on the morphology, tensile properties, resilience, and thermal properties of the resultant samples. Bead‐free and fine interconnected nanofibers were obtained with an increase of acetone content up to 60 wt%. The total physical properties of the blended nonwovens were optimal for a DMAc/acetone ratio of 40/60, in which the tensile load at break, extension at break and Young's modulus were 441, 54, and 256% higher than that of pure ramie web, respectively. The resilience of the blended nonwovens was ~20% higher than that of nonblended ramie web. The significant improvement of physical properties may be due to the good connection between PU nanofiber membranes and ramie webs and the molecular chain structure differences, interconnected structural differences, and high extensibility of PU nanofibers, according to the results of crystallization by differential scanning calorimetry (DSC) and morphological observation by scanning electronic microscopy (SEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1–14, 2010 相似文献
133.
D. Monzon-Hernandez A. N. Starodumov A. R. Boyain y Goitia V. N. Filippov V. P. Minkovich P. Gavrilovic 《Optics Communications》1999,170(4-6):241-246
Modal birefringence and stress distribution measurements in a single-mode double-clad Nd+3-doped fiber are reported. The contribution of different mechanisms, such as stress-induced birefringence, bending and core ellipticity, to the total birefringence is determined for a fiber wound onto a drum. A stress distribution pattern in the cross-section of the fiber is presented. The stresses are shown to be applied to a fiber core along the cladding minor axis. 相似文献
134.
Zhongbing Huang Xiaoming Liao Yunqing Kang Guangfu Yin Yadong Yao 《Journal of colloid and interface science》2009,330(2):399-403
Why is it that drops do not slip down inclined thin fibers or spider silks? The possible explanation is based on the existence of fiber size, which causes a sustaining force that pins these drops. Following this explanation, the drop remains in equilibrium until a critical value of the sustaining force is reached. We suggest an alternative analyses, from the point of view of the inclined fiber at which the drop slips down is predicted. This result does not depend explicitly on silk surface roughness, but only on the drop size and surface tensions. 相似文献
135.
In this paper, an extended finite difference time domain (FDTD) algorithm for the full-vectorial analysis of photonic crystal
fibers has been derived. For achieving a good convergence and high accuracy, a kind of modified conformal FDTD method has
been applied. An anisotropic perfectly matched layer for truncation of boundary conditions has been introduced. Material and
chromatic dispersions are numerically investigated for the photonic crystal fibers with different dimensions and geometrical
parameters and different dispersion behaviors are exhibited. 相似文献
136.
Steve Lien‐Chung Hsu Kuen‐Shian Lin Chi Wang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(24):8159-8169
Polybenzoxazole (PBO) fibers with a submicron diameter were successfully prepared by electrospinning its precursor, polyhydroxyamide (PHA), solutions to obtain the PHA fibers first, followed by appropriate thermal treatments for cyclization reaction. BisAPAF‐IC PHA with two different molecular weights (MWs) were synthesized from a low temperature polymerization of 2,2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane (BisAPAF) and isophthaloyl chloride (IC). Using dimethylacetamide (DMAc) and tetrahydrofuran (THF), solvent effects on the electrospinnability of PHA solutions were investigated. For balancing the solution properties, it was found that DMAc/THF mixture with a weight ratio of 1/9 was the best cosolvent to prepare smooth PHA fibers; uniform PHA fibers with a diameter of 325–720 nm were obtained by using 20 wt % PHA/(DMAc/THF) solutions. For a fixed PHA concentration, solutions with a lower MW of PHA yielded thinner electrospun fibers under the same electrospinning condition. After obtaining the electrospun BisAPAF‐IC PHA fibers, subsequent thermal cyclization up to 350 °C produced the corresponding thermally stable BisAPAF‐IC PBO fibers with a diameter of 305–645 nm. The structure of the precursor fibers and the fully cyclized fibers were characterized by FTIR. For the cyclized BisAPAF‐IC PBO fibers, thermogravimetric analysis showed a 5% weight loss temperature at 523 °C in nitrogen atmosphere. The interconnected fiber structure in the BisAPAF‐IC PBO fiber mats was irrelevant to the curing process, but resulted from the jet merging during the whipping process as revealed by the high speed camera images. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8159–8169, 2008 相似文献
137.
138.
A new type of thermally conductive fibers based on silver coated wollastonite was prepared and characterized. The fibers were used for the preparation of elastic, highly thermally conductive polymeric composites based on ethylene-vinylacetate copolymer (EVA). It was shown that silver coated fibers significantly improved the thermal conductivity of composites despite the low silver volume content. The experimental results were discussed and compared to various theoretical models. The specific heat and the specific density of the composites were also characterized and reported. 相似文献
139.
A. Andres Leal Joseph M. Deitzel Steven H. McKnight John W. Gillespie Jr. 《Journal of Polymer Science.Polymer Physics》2009,47(18):1809-1824
Poly‐pyridobisimiazole (M5) single filaments subjected to varying degrees of heat treatment have been analyzed using Fourier Transform Infrared (FTIR) microspectroscopy in transmission mode to detect changes in the state of intermolecular hydrogen bonding as a function of fiber annealing conditions. The FTIR absorbance bands associated with hydrogen bonding in M5 fiber have been identified, and the integrated molar absorption coefficients for the bands of interest have been determined experimentally, which allows to quantify the concentration of N? H vibration groups hydrogen‐bonded (H‐bonded) to water molecules, and the concentration of N? H vibration groups H‐bonded to adjacent polymer chains in the fiber. A dual mechanism kinetic rate expression is used to describe intermolecular H‐bond formation in M5 fiber as a function of annealing conditions, from which an activation energy for H‐bond formation of 14.8 kJ/mol is obtained. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1809–1824, 2009 相似文献
140.
Pan Peng Yi‐Zhang Chen Yan‐Fang Gao Jian Yu Zhao‐Xia Guo 《Journal of Polymer Science.Polymer Physics》2009,47(19):1853-1859
Polyoxymethylene/thermoplastic polyurethane (POM/TPU) blends containing 10–30 wt % of TPU were electrospun using hexafluoroisopropanol as the solvent. The average fiber diameter increases with the increase in TPU content from 0.68 μm for neat POM fibers to 0.92 μm for POM/TPU 7:3 blend fibers due to the increase in solution viscosity. Core/sheath structure with the major component POM as the core and the minor component TPU as the sheath was observed by transmission electron microscopy and further confirmed by surface N contents of the blend fiber mats. The crystalline melting point and the degree of crystallinity of POM have no obvious change by coelectrospinning with TPU due to lack of interaction between POM and TPU as revealed by Fourier transform infrared spectroscopy. Tensile tests showed that the unusual high ductility of POM fiber mat could be further increased by coelectrospinning with 10 or 20 wt % TPU without significantly decreasing the stiffness and strength. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1853–1859, 2009 相似文献