Organoboron compounds as Lewis acid receptors of fluoride ions in polymeric membranes

2012 ◽  
Vol 733 ◽  
pp. 71-77 ◽  
Author(s):  
Martyna Jańczyk ◽  
Agnieszka Adamczyk-Woźniak ◽  
Andrzej Sporzyński ◽  
Wojciech Wróblewski
Keyword(s):  
Lewis Acid ◽  
Polymeric Membranes ◽  
Fluoride Ions ◽  
Organoboron Compounds

scholarly journals P2.1.11 Fluoride sensing by polymeric membranes based on organoboron Lewis acid receptors

2012 ◽  
Author(s):  
Martyna Janczyk ◽  
Wojciech Wróblewski ◽  
Agnieszka Adamczyk-Wózniak ◽  
Andrzej Sporzynski
Keyword(s):  
Lewis Acid ◽  
Polymeric Membranes ◽  
Fluoride Sensing

Organoboron compounds as mild nucleophiles in Lewis acid- and transition metal-catalyzed C­C bond-forming reactions

2002 ◽  
Vol 74 (1) ◽  
pp. 43-55 ◽  
Author(s):  
Robert A. Batey ◽  
Tan D. Quach ◽  
Ming Shen ◽  
Avinash N. Thadani ◽  
David V. Smil ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Coupling Reactions ◽  
Rhodium Catalysis ◽  
Organoboron Compounds ◽  
Bond Forming ◽  
Acyliminium Ions ◽  
Cross Coupling Reactions ◽  
Bond Forming Reactions ◽  
Palladium Catalyzed ◽  
Metal Catalyzed

The use of air- and water-stable organoboron compounds for C­C bond-forming reactions are reported. These studies include the Lewis acid-promoted additions of boronic esters to N-acyliminium ions and allyl and crotyltrifluoroborate salts to aldehydes. Aryl and alkenyltrifluoroborate salts will add to aldehydes under the influence of rhodium catalysis or in the presence of zinc metal. These salts also participate in palladium-catalyzed Suzuki­Miyaura and other cross-coupling reactions. Finally, a new type of N-heterocyclic carbene ligand is reported and used for Pd-catalyzed Suzuki­Miyaura couplings.

scholarly journals Metal-free glycosylation with glycosyl fluorides in liquid SO2

2021 ◽  
Vol 17 ◽  
pp. 964-976
Author(s):  
Krista Gulbe ◽  
Jevgeņija Lugiņina ◽  
Edijs Jansons ◽  
Artis Kinens ◽  
Māris Turks
Keyword(s):  
Nmr Spectroscopy ◽  
Sulfur Dioxide ◽  
Lewis Acid ◽  
Polar Solvent ◽  
Ion Pairs ◽  
Fluoride Ions ◽  
Acid Properties ◽  
Metal Free ◽  
Temperature Regimes ◽  
Ionic Compounds

Liquid SO2 is a polar solvent that dissolves both covalent and ionic compounds. Sulfur dioxide possesses also Lewis acid properties, including the ability to covalently bind Lewis basic fluoride ions in a relatively stable fluorosulfite anion (FSO2 −). Herein we report the application of liquid SO2 as a promoting solvent for glycosylation with glycosyl fluorides without any external additive. By using various temperature regimes, the method is applied for both armed and disarmed glucose and mannose-derived glycosyl fluorides in moderate to excellent yields. A series of pivaloyl-protected O- and S-mannosides, as well as one example of a C-mannoside, are synthesized to demonstrate the scope of the glycosyl acceptors. The formation of the fluorosulfite species during the glycosylation with glycosyl fluorides in liquid SO2 is proved by 19F NMR spectroscopy. A sulfur dioxide-assisted glycosylation mechanism that proceeds via solvent separated ion pairs is proposed, whereas the observed α,β-selectivity is substrate-controlled and depends on the thermodynamic equilibrium.

SEM/FESEM imaging of lamellar structures in melt extruded polyethylene films

1992 ◽  
Vol 50 (2) ◽  
pp. 1142-1143
Author(s):  
R.T. Chen ◽  
M.G. Jamieson ◽  
R. Callahan
Keyword(s):  
Imaging Techniques ◽  
Membrane Surface ◽  
High Stress ◽  
Extrusion Direction ◽  
Polymeric Membranes ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Crystalline Polymers ◽  
Lamellar Structures ◽  
Resolution Imaging

“Row lamellar” structures have previously been observed when highly crystalline polymers are melt-extruded and recrystallized under high stress. With annealing to perfect the stacked lamellar superstructure and subsequent stretching in the machine (extrusion) direction, slit-like micropores form between the stacked lamellae. This process has been adopted to produce polymeric membranes on a commercial scale with controlled microporous structures. In order to produce the desired pore morphology, row lamellar structures must be established in the membrane precursors, i.e., as-extruded and annealed polymer films or hollow fibers. Due to the lack of pronounced surface topography, the lamellar structures have typically been investigated by replica-TEM, an indirect and time consuming procedure. Recently, with the availability of high resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM), the microporous structures on the membrane surface as well as lamellar structures in the precursors can be directly examined.The materials investigated are Celgard® polyethylene (PE) flat sheet membranes and their film precursors, both as-extruded and annealed, made at different extrusion rates (E.R.).

Low-voltage field-emission SEM of polymeric membranes for glucose biosensors

1990 ◽  
Vol 48 (3) ◽  
pp. 860-861
Author(s):  
Lorna K. Mayo ◽  
Kenneth C. Moore ◽  
Mark A. Arnold
Keyword(s):  
Glucose Sensor ◽  
Low Voltage ◽  
Glucose Sensors ◽  
Polymeric Membranes ◽  
Artificial Endocrine Pancreas ◽  
Self Monitoring ◽  
Conducting Materials ◽  
Insulin Dependent ◽  
Living Tissues ◽  
Voltage Scanning

An implantable artificial endocrine pancreas consisting of a glucose sensor and a closed-loop insulin delivery system could potentially replace the need for glucose self-monitoring and regulation among insulin dependent diabetics. Achieving such a break through largely depends on the development of an appropriate, biocompatible membrane for the sensor. Biocompatibility is crucial since changes in the glucose sensors membrane resulting from attack by orinter action with living tissues can interfere with sensor reliability and accuracy. If such interactions can be understood, however, compensations can be made for their effects. Current polymer technology offers several possible membranes that meet the unique chemical dynamics required of a glucose sensor. Two of the most promising polymer membranes are polytetrafluoroethylene (PTFE) and silicone (Si). Low-voltage scanning electron microscopy, which is an excellent technique for characterizing a variety of polymeric and non-conducting materials, 27 was applied to the examination of experimental sensor membranes.

Column: Polymeric Membranes

Polymer News ◽  
2004 ◽  
Vol 29 (8) ◽  
pp. 253-257
Author(s):  
Tejraj Aminabhavi ◽  
Udaya Toti ◽  
Mahaveer Kurkuri ◽  
Nadagouda Mallikarjuna ◽  
Lakshmi Shetti
Keyword(s):  
Polymeric Membranes

Solutocapillary-convection-driven macrovoid defect formation in polymeric membranes

2001 ◽  
Author(s):  
J. Zartman ◽  
V. Khare ◽  
A. Greenberg ◽  
M. Pekny ◽  
P. Todd ◽  
...  
Keyword(s):  
Defect Formation ◽  
Polymeric Membranes
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