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931.
Yousef Shafieyan Shahriar Sharifi Mohammad Imani Mohammad Ali Shokrgozar Neda Aboudzadeh Mohammad Atai 《先进技术聚合物》2011,22(12):2182-2190
Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and 1H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
932.
Jie He Chengli Yang Xiaohui Xiong Biwang Jiang 《Journal of polymer science. Part A, Polymer chemistry》2012,50(14):2889-2897
A novel method for the preparation of monodisperse porous silica microspheres with controllable morphology and structure is reported. The starting porous polymer microspheres were first functionalized with ethylenediamine (EDA) to generate amino groups. Subsequently, silica nanoparticles were deposited in the porous polymer microsphere to form polymer/silica hybrid microspheres via a modified sol‐gel process in the presence of tetra‐n‐butylammonium bromide (TBAB) or tetramethyl ammonium hydroxide (TMAH). Upon calcination of the polymer/silica hybrid microspheres, the porous silica microspheres were obtained. The morphology, inner structure, and properties of the porous silica microspheres were studied by field emission scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mercury intrusion method. The results show that the presence of TBAB or TMAH in the process not only prevents the agglomeration of the hybrid microspheres, but also governs the controllable morphology from a porous inner structure to a hollow‐cage structure. The obtained porous silica microspheres exhibit no shrinkage from the polymer microspheres with a yield of around 98%. These porous silica microspheres have potential applications in the fields of chromatography, catalyst, and biology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
933.
A convection–diffusion porous media model for moisture transport in polymer composites: Model development and validation 下载免费PDF全文
Liangbiao Chen Hsing‐Wei Chu Xuejun Fan 《Journal of Polymer Science.Polymer Physics》2015,53(20):1440-1449
Moisture may cause many detrimental effects to polymers and their composites, thus inhibiting the applications of polymeric materials in hot and humid environments. In this article, a convection–diffusion porous media model is derived to better characterize rapid moisture transport in polymer composites at high temperatures. The model considers both continuum diffusion in solid and high‐pressure convection taking place in the pore network. Coupling of convection and diffusion is achieved by combining the law of conservation of mass, Darcy's law, the liquid–vapor chemical equilibrium, and the ideal gas law. The presented model is validated by conducting experimental tests on an epoxy compound. It is found that the proposed convection–diffusion model is more effective than diffusion‐only and convection‐only models for interpreting rapid desorption tests at high temperatures. A numerical study is also performed to predict maximum vapor pressure during a rapid heating process. Vapor pressure is found to be as high as 6.5 MPa at a heating rate of 10 K/s. It is concluded that the convection–diffusion model is able to capture both vapor dynamics and diffusion mechanism in porous polymeric materials, and can be potentially used to further investigate polymer‐moisture interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1440–1449 相似文献
934.
Dr. Yun Qiao Dr. Keishiro Tahara Prof. Qian Zhang Prof. Xi‐Ming Song Prof. Jun‐ichi Kikuchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1340-1348
Anionic cerasomes, which consist of a liposomal lipid bilayer and a ceramic surface, were used as a soft interface for the construction of an integrated modified electrode to achieve the transmission of chemical information from a redox enzyme through electrical signals. The morphological properties of the cerasomes were systematically compared with those of two structural analogues, namely, liposomes and silica nanoparticles. The results indicated that the cerasomes combined the advantages of liposomes and silica nanoparticles. The lipid bilayer gave excellent biocompatibility, as in the case of liposomes, and high structural stability, similar to that of silica nanoparticles, was derived from the silicate framework on the cerasome surface. The performance at the electrochemical interface created by means of a combination of cerasomes and horseradish peroxidase on a glassy carbon electrode was much better than those achieved with liposomes or silica nanoparticles instead of cerasomes. The potential use of cerasomes in the construction of supramolecular devices for mediator‐free biosensing was evaluated. 相似文献
935.
Pineapple leaf fiber (PALF), used as a reinforcing agent, does not have good adhesion to natural rubber (NR) due to the difference in their polarities. As a result, the degree of reinforcement of NR imparted by PALF remains low compared to that in a polar rubber like acrylonitrile butadiene (NBR). One of the factors that determines the adhesion between the rubber and the reinforcement is the rubber molecular weight. Thus, the aim of this paper is to demonstrate that the stress at very low strains of short pineapple leaf fiber (PALF) reinforced natural rubber (NR) can be significantly increased by lowering the matrix molecular weight. This can be achieved by increasing the matrix mastication time. The composites studied here contain a fixed amount of PALF at 10 part (by weight) per hundred rubber (phr). The PALF fibers were both untreated (UPALF) and sodium hydroxide treated (TPALF). Mastication times of 2, 4, 8 and 16 min were used. Stress-strain curves of PALF reinforced NR prepared with different mastication times were then compared. The most affected region of the curve is in the low strain region. The slopes of the stress-strain curves (moduli) increase with increasing mastication time, indicating better fiber-rubber interaction. The maximum stress achieved at 10% strain is almost 370% that obtained with the usual short mastication time (2 min). The effect remains up to very high strains, although becoming smaller as the strain is increased. Hence, we demonstrate that, by using long enough mastication time, stress-strain curves and stress at low strain of PALF reinforced NR can be improved without the need of any other adhesion promoters. 相似文献
936.
Lewis B. Tunnicliffe Alan G. Thomas James J. C. Busfield 《Journal of Polymer Science.Polymer Physics》2011,49(15):1084-1092
The effect of silica nanofiller surface chemistry on compounded particle size and high strain particle dewetting in a semitransparent nanosilica‐filled elastomer composite was determined using backscattered visible light and transmitted light, respectively. The integrated intensities of backscattered light from the samples were collected at various visible wavelengths for thin‐film composites using ultraviolet–visible spectrometer with an integrating sphere. The data revealed strong Rayleigh‐type scattering from compounded filler particles. Size information was extracted and found to broadly correlate with scanning electron microscopy image analysis of fracture surface. Incorporation of a siloxane surface treatment chemical during compounding resulted in a reduced average filler particle size in the cured composite. On extension of the samples, an optical transition was observed only in the filled composites. At high strains, the semi transparent samples displayed an abrupt drop in transparency becoming opaque. This was quantified using a simple light transmission‐sample extension technique. Strain‐induced crystallization was discounted as the cause for the transition by X‐ray diffraction analysis. The onset yield stress for the optical transition was found to be filler surface‐chemistry‐dependent with the siloxane‐treated filler exhibiting a greatly increased onset stress value. These observations were discussed and rationalized in terms of filler particle–matrix dewetting and cavitation at high strains. Matrix–filler dewetting was distinguished from matrix cavitation by comparison with Beer–Lambert behavior derived from unstrained samples. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011. 相似文献
937.
Dae Kyom Kim Minsik Hwang Jan P. F. Lagerwall 《Journal of Polymer Science.Polymer Physics》2013,51(11):855-867
A recently introduced new branch of applied polymer science is the production of highly functional and responsive fiber mats by means of electrospinning polymers that include liquid crystals. The liquid crystal, which provides the responsiveness, is most often contained inside fibers of core‐sheath geometry, produced via coaxial electrospinning, but it may also be inherent to the polymer itself, for example, in case of liquid crystal elastomers. The first experiments served as proof of concept and to elucidate the basic behavior of the liquid crystal in the fibers, and the field is now ripe for more applied research targeting novel devices, in particular in the realm of wearable technology. In this perspective, we provide a bird's eye view of the current state of the art of liquid crystal electrospinning, as well as of some relevant recent developments in the general electrospinning and liquid crystal research areas, allowing us to sketch a picture of where this young research field and its applications may be heading in the next few years. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013, 51, 855–867 相似文献
938.
Nanocomposite Made of an Oligo(p‐phenylenevinylene)‐Based Trihybrid Thixotropic Metallo(organo)gel Comprising Nanoscale Metal–Organic Particles,Carbon Nanohorns,and Silver Nanoparticles 下载免费PDF全文
Subham Bhattacharjee Dr. Suman K. Samanta Parikshit Moitra K. Pramoda Ram Kumar Prof. Dr. Santanu Bhattacharya Prof. Dr. C. N. R. Rao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5467-5476
A silver ion (Ag+)‐triggered thixotropic metallo(organo)gel of p‐pyridyl‐appended oligo(p‐phenylenevinylene) derivatives (OPVs) is reported for the first time. Solubilization of single‐walled carbon nanohorns (SWCNHs) in solutions of the pure OPVs as well as in the metallogels mediated by π–π interactions has also been achieved. In situ fabrication of silver nanoparticles (AgNPs) in the SWCNH‐doped dihybrid gel leads to the formation of a trihybrid metallogel. The mechanical strength of the metallogels could be increased stepwise in the order: freshly prepared gel<dihybrid gel<trihybrid gel. Microscopic studies of the trihybrid gel indicate the formation of three distinct morphologies, that is, nanoscale metal–organic particles (NMOPs), flowerlike aggregates of SWCNHs and AgNPs, and also their integration with each other. Detailed studies suggest lamellar organizations of the linear metal–ligand complexes in the NMOPs, which upon association create a three‐dimensional network that eventually immobilizes the solvent molecules. 相似文献
939.
Short glass fiber reinforced polypropylene (sgf-PP) is increasingly used in the automotive industry with the impact properties as key parameter. Experimentally, the impact behavior strongly depends on the specimen design, test set-up as well as temperature, and thus the characterization method should always be attuned to the occurring impact conditions of the final part. However, in order to deduce some general design criteria for sgf-PP, in this study a wide range of experimental parameters were investigated, specially focusing also on the effect of the governing, local fiber orientation distribution (FOD). Therefore, the effects of stress state (tensile, puncture and bending test), amount of stress concentration (notch radius) and temperature are characterized and discussed. The results proved that, as expected, distinctly different levels of impact strength and different dependencies on notches and notch radii are obtained for the various test set-ups. However, similarities in the temperature dependence are observed for specimens with similar governing fiber orientation. 相似文献
940.
《Comptes Rendus Mecanique》2017,345(11):742-751
This article addresses the asymptotic response of viscoelastic heterogeneous media in the frequency domain, at high and low frequencies, for different types of elementary linear viscoelastic constituents. By resorting to stationary principles for complex viscoelasticity and adopting a classification of the viscoelastic behaviours based on the nature of their asymptotic regimes, either elastic or viscous, four exact relations are obtained on the overall viscoelastic complex moduli in each case. Two relations are related to the asymptotic uncoupled heterogeneous problems, while the two remaining ones result from the viscoelastic coupling that manifests itself in the transient regime. These results also provide exact conditions on certain integrals in time of the effective relaxation spectrum. This general setting encompasses the results obtained in preceding studies on mixtures of Maxwell constituents [1], [2]. 相似文献