An Electron Microscopic Study Of Some Solid-State Polymerization Reactions

1977 ◽  
Vol 35 ◽  
pp. 170-171
Author(s):  
William Jones ◽  
John M. Thomas ◽  
David A. Livesley
Keyword(s):  
Molecular Weight ◽  
Solid State ◽  
Perfect Crystal ◽  
Degree Of Crystallinity ◽  
Electron Microscopic ◽  
Crystalline Polymers ◽  
Transmission Electron ◽  
Organic Solid ◽  
High Degree ◽  
Molecular Weight Product

There is interest at present amongst organic solid-state chemists in producing, through topochemical reaction, stereoregular and crystalline polymers of high molecular weight. In certain reactions the geometry of the polymer product and the high degree of crystallinity are completely determined by the molecular packing in the monomer crystal (1). In others, however, low molecular weight product or products not predicted from a knowledge of the monomer packing have lead to suggestions that dislocations or other regions of imperfection may be important as sites of initiation of reaction or possibly of nucleation of the formed polymer (2). Defects will also control the length of the formed polymer (2).We have utilized transmission electron microscopy for investigating defects in anthracene and some of its derivatives, which also undergo chemical and photo-induced reactions, occasionally in a manner not determined by the perfect crystal lattice (3). Consequently we felt it appropriate to observe by TEM foils of monomer before, during and after polymerization.

scholarly journals Solid-State Polymerization of Poly(Ethylene Furanoate) Biobased Polyester, III: Extended Study on Effect of Catalyst Type on Molecular Weight Increase

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 438 ◽  
Author(s):  
Yosra Chebbi ◽  
Nejib Kasmi ◽  
Mustapha Majdoub ◽  
George Papageorgiou ◽  
Dimitris Achilias ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Solid State ◽  
Intrinsic Viscosity ◽  
Weight Increase ◽  
Degree Of Crystallinity ◽  
Solid State Polymerization ◽  
End Groups ◽  
Poly Ethylene ◽  
Molecular Weight Increase

In this study, the synthesis of poly(ethylene furanoate) (PEF), catalyzed by five different catalysts—antimony acetate (III) (Sb Ac), zirconium (IV) isopropoxide isopropanal (Zr Is Ip), antimony (III) oxide (Sb Ox), zirconium (IV) 2,4-pentanedionate (Zr Pe) and germanium (IV) oxide (Ge Ox)—via an industrially common combination of melt polymerization and subsequent solid-state polymerization (SSP) is presented. In all reactions, proper amounts of 2,5-dimethylfuran-dicarboxylate (DMFD) and ethylene glycol (EG) in a molar ratio of DMFD/EG= 1/2 and 400 ppm of catalyst were used. Polyester samples were subjected to SSP procedure, under vacuum application, at different reaction times (1, 2, 3.5, and 5 h) and temperatures of 190, 200, and 205 °C. Carboxyl end-groups concentration (–COOH), intrinsic viscosity (IV), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polymers to study the effect of the used catalysts on the molecular weight increase of PEF during SSP process. As was expected, it was found that with increasing the SSP time and temperature, the intrinsic viscosity and the average molecular weight of PEF steadily increased. In contrast, the number of carboxyl end-groups content showed the opposite trend as intrinsic viscosity, that is, gradually decreasing during SSP time and temperature increase. It is worthy to note that thanks to the SSP process an obvious and continuous enhancement in the thermal properties of the prepared PEF samples was attained, in which their melting temperatures (Tm) and degree of crystallinity (Xc) increase progressively with increasing of reaction time and temperature. To predict the time evolution of polymers IV, as well as the hydroxyl and carboxyl content of PEF polyesters during the SSP, a simple kinetic model was developed. From both the theoretical simulation results and the experimental measurements, it was demonstrated that surely the Zr Is Ip catalyst shows the best catalytic characteristics compared to all other used catalysts herein, that is, leading in reducing—in a spectacular way—the activation energy of the involved both transesterification and esterification reactions during SSP.

Transmission Electron Microscopic Study Of Heteroepitaxial Mechanism Of Cvd-Dlamond Grown On Pt(Lll) Substrate.

1999 ◽  
Vol 5 (S2) ◽  
pp. 170-171
Author(s):  
Guofu Zhou ◽  
Yoshizo Takai ◽  
Ryuichi Shimizu
Keyword(s):  
Diamond Film ◽  
Electronic Devices ◽  
Chemical Properties ◽  
Atomic Scale ◽  
Diamond Growth ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Single Crystal Diamond ◽  
High Degree ◽  
Novel Devices

Owing to its unique and outstanding physical-chemical properties, diamond is considered to be one of the most important potential materials for applications such as in mechanical, optical, thermal, and electronic devices. Among them, the most attractive application of diamond would be a semiconductor for high temperature and high power electronic devices. To realize such novel devices, a high quality of defect-free single-crystal diamond film is required. Recently, continuous diamond films are found to be able to grow on Pt(lll) substrate. Since the diamond film synthesized on Pt shows a high degree of epitaxy, this approach has drawn the attention of reseafchers in this field and some research results have been reported. However, the heteroepitaxial mechanism is still to be elucidated; in particular, why does diamond grow heteroepitaxially on the Pt substrate and how do the atoms align in the interface between diamond and the Pt substrate? In order to solve those problems, it is very necessary to study the diamond growth mechanism on an atomic scale.

Heteroepitaxial Growth of Ba0.5Sr0.5TiO3/SrRuO3 on YSZ/Si by Off-Axis Sputtering

1994 ◽  
Vol 361 ◽  
Author(s):  
S.Y. Hou ◽  
J. Kwo ◽  
R.K. Watts ◽  
J.-Y. Cheng ◽  
R.J. Cava ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Degree Of Crystallinity ◽  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Dielectric Constant And Loss ◽  
Bst Films ◽  
High Degree ◽  
Room Temperature Dielectric Constant

ABSTRACTWe demonstrate an epitaxial heterostructure of Ba0.5Sr0.5 TiO3/SrRuO3/YSZ on Si for potential charge storage applications. The dielectric Ba0.5Sr0.5TiO3 (BST) and conductive oxide SrRuO3 are both grown (110) oriented on YSZ (100) buffered Si by 90° off-axis sputtering. These films showed a high degree of crystallinity with minimal interdiffusion at the interfaces as examined by X-ray diffraction, Rutherford backscattering spectroscopy, and cross-section transmission electron microscopy. The in-plane epitaxial alignment of the films is BST/SRO 〈111〉 // YSZ 〈110〉 with a four-fold degeneracy. The dielectric constant and loss tangent of the epi-BST films are 360 and 0.01 at 10 kHz. The leakage current density is < 4×10∼−7 A/cm2 at 1 V. The room temperature dielectric constant (ε) of the BST films shows a roll-off in the 1–10 MHz range. This is attributed to the existence of a series resistance in the measurement circuit, which likely arises from the SrRuO3 electrode.

Clay mineral mixtures as alteration products in pillow basalts from the eastern flank of Juan de Fuca Ridge: a TEM-AEM study

Clay Minerals ◽  
2001 ◽  
Vol 36 (1) ◽  
pp. 75-91 ◽  
Author(s):  
G. Giorgetti ◽  
P. Marescotti ◽  
R. Cabella ◽  
G. Lucchetti
Keyword(s):  
Electron Microscope ◽  
Juan De Fuca Ridge ◽  
Degree Of Crystallinity ◽  
Electron Microscopic ◽  
Fuca Ridge ◽  
Altered Sample ◽  
Transmission Electron ◽  
Juan De Fuca ◽  
Electron Microscopic Data ◽  
Fe Oxyhydroxides

AbstractTransmission electron microscope-analytical electron microscope analyses have been carried out on secondary minerals from pillow basalts with various degrees of alteration from the Juan de Fuca Ridge (ODP Leg 168). The electron microscopic data indicate that the alteration products consist mainly of phyllosilicate mixtures. The least altered sample shows poorly crystalline phyllosilicates occurrring as flakes with 10 Å -spaced lattice fringes. They have compositions of celadonite mixed with smectite and/or Fe oxyhydroxides and Mg-rich smectite. Proceeding towards older, more altered basalts, the alteration products consist of: (1) poorly crystalline celadonite mixtures and Mg-rich smectite; and (2) phyllosilicates with a higher degree of crystallinity, showing lattice fringes with 9.1 Å -spacing and with a talc-like composition. Changes in phyllosilicate association occur as the type of alteration changes from an oxidizing, water-dominated system (occurrence of celadonite mixtures with Fe hydroxides) to a reducing, rock-dominated system (occurrence of Fe-smectite and talc-like mixtures).

SYNTHESIS OF YTTRIA-STABILIZED CUBIC ZIRCONIA NANOCRYSTALS BY ULTRASONIC–MICROWAVE ROUTE

NANO ◽  
2010 ◽  
Vol 05 (05) ◽  
pp. 271-277 ◽  
Author(s):  
JIAN-DONG WANG ◽  
CHONG-XIAO LUO ◽  
JIN-KU LIU ◽  
YI LU ◽  
GUANG-MING LI
Keyword(s):  
Average Particle Size ◽  
Degree Of Crystallinity ◽  
Average Particle ◽  
Stabilized Zirconia ◽  
Uniform Size ◽  
X Ray ◽  
Microwave Assisted ◽  
Transmission Electron ◽  
High Degree ◽  
Microwave Assisted Method

The yttria-stabilized zirconia (YSZ) nanocrystals with uniform size, high purity, and high degree of crystallinity, were prepared by ultrasonic–microwave-assisted method. The structure, optical properties and morphologies of YSZ nanocrystals were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, UV–vis absorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The SEM and TEM images of the YSZ nanocrystals indicate that the product is a mono-dispersion structure with an average particle size of about 25 nm.

Preparation and Microwave Absorption Properties of CNTs/HAp Composites for Use in Tumor Hyperthermia

2011 ◽  
Vol 345 ◽  
pp. 280-286
Author(s):  
Ai Hong Liu
Keyword(s):  
Hydrothermal Treatment ◽  
Treatment Method ◽  
Pure Component ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Microwave Absorption Properties ◽  
Seed Material ◽  
Transmission Electron ◽  
Tumor Hyperthermia ◽  
High Degree

CNTs/HAp thermo-seed material were prepared by a simple and effective coprecipitation and hydrothermal treatment method. The phase structure, composition and morphology of CNTs/HAp composites were examined by X-ray diffraction (XRD), transmission electron microscope (TEM). The results showed that When CNTs content was 10wt%, after hydrothermal treatment, a certain high degree of crystallinity, pure component single HAp layer was obtained on the surface of CNTs successfully. The electromagnetic parameters of CNTs/HAp composites were measured in the range from 0 GHz to 5.0 GHz. The results showed that CNTs/HAp composite had better absorbing properties in the 0-5.0 GHz range. With increasing of CNTs content, the microwave absorbing capacity of CNTs/HAp composite had been gradually strengthened, the absorption peak moved towards high frequency, the bandwidth was increased. When CNTs content was 8wt%, a maximum reflection loss value of -26 dB had been obtained at 3.0 GHz. Therefore, CNTs/HAp composite material is expected as thermo-seed material for tumor hyperthermia.

scholarly journals First evidence of high-molecular-weight bacteriocin (tailocin) produced by Antarctic Pseudomonas spp.

2018 ◽  
Vol 8 (2) ◽  
pp. 178-185
Author(s):  
Kateřina Snopková ◽  
Ivo Sedláček ◽  
David Šmajs
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polar Regions ◽  
Electron Microscopic ◽  
Pseudomonas Spp ◽  
Transmission Electron ◽  
Soil Ecosystems ◽  
James Ross Island ◽  
Inhibitory Agents ◽  
Dynamic Communities

Cold-adapted soil ecosystems represent dynamic communities varying in a structure, microbial abundance and metabolic activity. To antagonize competitors, soil bacteria produce a variety of inhibitory agents. We tested production of antimicrobials in Pseudomonas spp. isolated in James Ross Island, Antarctica, and performed transmission electron microscopic analyses of selected high-molecular-weight bacteriocin particles. The dimensions of R-tailocins produced by Pseudomonas sp. P2422 were 168 ± 2.0nm (length) and 16 ± 0.8nm (width) thus representing one of the largest tailocins secreted by Pseudomonas spp. To our knowledge, this is the first evidence of tailocin production by bacteria originated from polar regions.

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