scholarly journals Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

2015 ◽  
Vol 11 ◽  
pp. 1796-1808 ◽  
Author(s):  
Yulia I Denisova ◽  
Maria L Gringolts ◽  
Alexander S Peregudov ◽  
Liya B Krentsel ◽  
Ekaterina A Litmanovich ◽  
...  
Keyword(s):  
Random Copolymer ◽  
Polymer Chains ◽  
Ex Situ ◽  
Polymer Mixture ◽  
Second Stage ◽  
Cross Metathesis ◽  
Whole Process ◽  
Low Concentrations ◽  
Kinetics Of

The cross-metathesis of polynorbornene and polyoctenamer in d-chloroform mediated by the 1st generation Grubbs’ catalyst Cl2(PCy3)2Ru=CHPh is studied by monitoring the kinetics of carbene transformation and evolution of the dyad composition of polymer chains with in situ 1H and ex situ 13C NMR spectroscopy. The results are interpreted in terms of a simple kinetic two-stage model. At the first stage of the reaction all Ru-benzylidene carbenes are transformed into Ru-polyoctenamers within an hour, while the polymer molar mass is considerably decreased. The second stage actually including interpolymeric reactions proceeds much slower and takes one day or more to achieve a random copolymer of norbornene and cyclooctene. Its rate is limited by the interaction of polyoctenamer-bound carbenes with polynorbornene units, which is hampered, presumably due to steric reasons. Polynorbornene-bound carbenes are detected in very low concentrations throughout the whole process thus indicating their higher reactivity, as compared with the polyoctenamer-bound ones. Macroscopic homogeneity of the reacting media is proved by dynamic light scattering from solutions containing the polymer mixture and its components. In general, the studied process can be considered as a new way to unsaturated multiblock statistical copolymers. Their structure can be controlled by the amount of catalyst, mixture composition, and reaction time. It is remarkable that this goal can be achieved with a catalyst that is not suitable for ring-opening metathesis copolymerization of norbornene and cis-cyclooctene because of their substantially different monomer reactivities.

Advantage of In-situ over Ex-situ techniques as reliability tool: Aging kinetics of Imec’s MCM-D discrete passives devices.

2003 ◽  
Vol 43 (9-11) ◽  
pp. 1785-1790
Author(s):  
P. Soussan ◽  
G. Lekens ◽  
R. Dreesen ◽  
W. De Ceuninck ◽  
E. Beyne
Keyword(s):  
Ex Situ ◽  
Aging Kinetics ◽  
Kinetics Of

Highly explosive basaltic eruptions: magma fragmentation induced by rapid crystallisation

2020 ◽  
Author(s):  
Fabio Arzilli ◽  
Giuseppe La Spina ◽  
Mike R. Burton ◽  
Margherita Polacci ◽  
Nolwenn Le Gall ◽  
...  
Keyword(s):  
Ex Situ ◽  
Explosive Eruptions ◽  
In Situ Observation ◽  
Sudden Increase ◽  
Crystallisation Kinetics ◽  
Magma Fragmentation ◽  
Crystallization Experiments ◽  
Basaltic Magmas ◽  
Kinetics Of

<p>Basaltic eruptions are the most common form of volcanism on Earth and planetary bodies. The low viscosity of basaltic magmas generally favours effusive and mildly explosive volcanic activity. Highly explosive basaltic eruptions occur less frequently and their eruption mechanism still remains subject to debate, with implications for the significant hazard associated with explosive basaltic volcanism. Particularly, highly explosive eruptions require magma fragmentation, yet it is unclear how basaltic magmas can reach the fragmentation threshold.</p><p>In volcanic conduits, the crystallisation kinetics of an ascending magma are driven by degassing and cooling. So far, the crystallisation kinetics of magmas have been estimated through ex situ crystallization experiments. However, this experimental approach induces underestimation of crystallization kinetics in silicate melts. The   crystallization experiments reported in this study were performed in situ at Diamond Light Source (experiment EE12392 at the I12 beamline), Harwell, UK, using basalt from the 2001 Etna eruption as the starting material. We combined a bespoke high-temperature environmental cell with fast synchrotron X-ray microtomography to image the evolution of crystallization in real time. After 4 hours at sub-liquidus conditions (1170 °C and 1150 °C) the system was perturbed through a rapid cooling (0.4 °C/s), inducing a sudden increase of undercooling. Our study reports the first in situ observation of exceptionally rapid plagioclase and clinopyroxene crystallisation in trachybasaltic magmas. We combine these constraints on crystallisation kinetics and viscosity evolution with a numerical conduit model to show that exceptionally rapid syn-eruptive crystallisation is the fundamental process required to trigger basaltic magma fragmentation under high strain rates. Our in situ experimental and natural observations combined with a numerical conduit model allow us to conclude that pre-eruptive temperatures <1,100°C can promote highly explosive basaltic eruptions, such as Plinian volcanism, in which fragmentation is induced by fast syn-eruptive crystal growth under high undercooling and high decompression rates. This implies that all basaltic systems on Earth have the potential to produce powerful explosive eruptions.</p>

Direct Observation of Single Displacement Cascade in Pyrochlore by Tv-Rate In-Situ TEM and Ex-Situ HRTEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 408-409
Author(s):  
J. Lian ◽  
L. M. Wang ◽  
S. X. Wang ◽  
R. C. Ewing
Keyword(s):  
Ion Irradiation ◽  
Heavy Ion ◽  
Ex Situ ◽  
In Situ Tem ◽  
Direct Impact ◽  
Displacement Cascade ◽  
Amorphous Domain ◽  
Rapid Kinetics ◽  
Kinetics Of

The ion irradiation-induced crystalline-to-amorphous transformation has been studied in many complex ceramics. Direct impact amorphization has been considered to be one of the fundamental amorphization mechanisms for complex ceramics under heavy ion irradiation . Based on the directimpact model, a highly energetic incident ion transfers its kinetic energy to the target as a thermal spike within 10“13 sec creating a “molten-like” displacement cascade, typically nanometer-scaled in diameter (as indicated by the result of a computer simulation in Fig. 1). This “molten” zone quickly quenches to a small amorphous domain within a few pico-seconds. Epitaxial recrystallization occurs around the amorphous/crystalline interface, so that the size of amorphous domains decrease with time. The accumulation and overlap of small amorphous domains eventually leads to complete amorphization of the irradiated material. Although the in-situTEM technique with the setup shown in Fig. 2 has been extensively applied to the study of the amorphization process in complex ceramics, most of the previous studies relied on in-situobservation of the electron diffraction pattern, and there has been a lack of solid evidence of direct impact amorphization due to the small nature of the cascades and the rapid kinetics of its evolution.

Degradation kinetics of ultrathin HfO2 layers on Si(100) during vacuum annealing monitored with in situ XPS/LEIS and ex situ AFM

2007 ◽  
Vol 47 (4-5) ◽  
pp. 657-659 ◽  
Author(s):  
A. Zenkevich ◽  
Yu. Lebedinskii ◽  
G. Scarel ◽  
M. Fanciulli ◽  
A. Baturin ◽  
...  
Keyword(s):  
Vacuum Annealing ◽  
Degradation Kinetics ◽  
Ex Situ ◽  
In Situ Xps ◽  
Kinetics Of

EFFECT OF PHBV CONTENT ON THE TRANSPARENCY AND SWELLING BEHAVIOR OF POLYMER/HECTORITE NANOCOMPOSITE HYDROGEL

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1365-1370 ◽  
Author(s):  
QINGSONG ZHANG ◽  
YIPING ZHAO ◽  
LI CHEN
Keyword(s):  
Gravimetric Method ◽  
Polymer Chains ◽  
Swelling Kinetics ◽  
Swelling Ratio ◽  
Nanocomposite Hydrogels ◽  
Cross Linker ◽  
Kinetics Of ◽  
Inorganic Network ◽  
Pure Poly

As a kind of novel biopolymer material with good biodegradability and biocompatibility, poly(β-hydroxybutyrate-co-valerate)(PHBV) was introduced into organic/inorganic network structure of nanocomposite hydrogels prepared by in-situ free-radical polymerization based on monomer N-isopropylacrylamide(NIPAM) and physical cross-linker hectorite. As viewed from appearance of the hydrogels, obvious change occurred from transparent to white with the increase of PHBV content, which reflects the structural shift from homogeneity to inhomogeneity. The swelling ratio and swelling kinetics of thermo-sensitive poly( NIPAM / PHBV /Hectorite) hydrogels with different PHBV content was investigated by gravimetric method. It was found that the incorporation of PHBV decreases the swelling ratio of pure poly( NIPAM /Hectorite) hydrogels on account of hydrophobicity of PHBV . Furthermore, in the case of swelling kinetics, the result of linear regression shows that relaxation of polymer chains of the hydrogels controls the swelling process.

Combustion reaction kinetics of char from in-situ or ex-situ pyrolysis of oil shale

Oil Shale ◽  
2019 ◽  
Vol 36 (3) ◽  
pp. 392
Author(s):  
Q Hong ◽  
Z Lei ◽  
Z Lidong ◽  
L Hongpeng ◽  
J Chunxia ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Oil Shale ◽  
Combustion Reaction ◽  
Ex Situ ◽  
Kinetics Of

X-ray diffraction diagnostic paired with gas gun driven compression of polyethylene

2019 ◽  
Author(s):  
Rachel C. Huber ◽  
Erik B. Watkins ◽  
Dana M. Dattelbaum ◽  
Richard L. Gustavsen
Keyword(s):  
Dynamic Compression ◽  
Polymer Chains ◽  
Extreme Condition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gas Gun ◽  
Gas Guns ◽  
Crystalline Domains ◽  
Kinetics Of

Abstract Understanding the kinetics of phase transitions, including decomposition from reactants to products under extreme condition events is challenging. Capturing these processes require: 1) diagnostics that probe on the timescales and at energies capable of interacting with the dynamically evolving products, penetrating the opaqueness of the changing system; and 2) detectors sensitive enough to observe these events. Synchrotrons and free electron lasers provide ke-V-energy x-ray beams capable of penetrating the optical-opaqueness of the temporally evolving products. At the Dynamic Compression Sector at the Advanced Photon Source, the x-ray beam is coupled to single and two-stage gas guns capable of producing planar shocks at a range of projectile velocities while capturing in situ x-ray diffraction/scattering of the evolving material under dynamic compression. In this work, we demonstrate the utility of this approach in measuring the evolution of crystalline domains in shocked high-density polyethylene to P = 7.45 GPa, and have observed the compression and orientation of the polymer chains in real time.

The mechanism and kinetics of the transformation from marcasite to pyrite: in situ and ex situ experiments and geological implications

2020 ◽  
Vol 175 (3) ◽  
Author(s):  
Xizhi Yao ◽  
Fang Xia ◽  
Artur P. Deditius ◽  
Joël Brugger ◽  
Barbara E. Etschmann ◽  
...  
Keyword(s):  
Ex Situ ◽  
Mechanism And Kinetics ◽  
Geological Implications ◽  
Kinetics Of
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