scholarly journals Sterically hindered malonamide monomers for the step growth synthesis of polyesters and polyamides

2014 ◽  
Vol 50 (73) ◽  
pp. 10665-10668 ◽  
Author(s):  
S. N. G. Tyler ◽  
R. L. Webster
Keyword(s):  
Molecular Weight ◽  
Lewis Acid ◽  
Mild Conditions ◽  
Step Growth ◽  
Sterically Hindered

Exploiting the ready cleavage of bulky amides in the presence of a simple nucleophile, a new monomer for step growth polymerisation has been realised. A range of novel polyesters and polyamides have been prepared under mild conditions that allow for efficient recycling and reuse of the amine by-product. The use of a Lewis acid to increase polyester molecular weight is also explored.

Ether Synthesis through Reductive Cross-Coupling of Ketones with Alcohols Using Me2SiHCl as both Reductant and Lewis Acid

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2425-2428 ◽  
Author(s):  
Bill Morandi ◽  
Yong Lee
Keyword(s):  
Functional Groups ◽  
Lewis Acid ◽  
Carbonyl Compounds ◽  
Cross Coupling ◽  
Wide Range ◽  
Direct Cross ◽  
Sterically Hindered ◽  
Polar Functional Groups ◽  
Ether Synthesis ◽  
Dialkyl Ethers

We report that a Lewis acidic silane, Me2SiHCl, can mediate the direct cross-coupling of a wide range of carbonyl compounds with alcohols to form dialkyl ethers. The reaction is operationally simple, tolerates a range of polar functional groups, can be utilized to make sterically hindered ethers, and is extendable to sulfur and nitrogen nucleo­philes.

Synthesis of Various Branched Ultra-High-Molecular-Weight Polyethylenes Using Sterically Hindered Acenaphthene-Based α-Diimine Ni(II) Catalysts

2018 ◽  
Vol 37 (15) ◽  
pp. 2442-2449 ◽  
Author(s):  
Lihua Guo ◽  
Kunbo Lian ◽  
Wenyu Kong ◽  
Shuai Xu ◽  
Guorun Jiang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Sterically Hindered ◽  
Ultra High Molecular Weight

Metathetical Degradation and Depolymerization of Unsaturated Polymers

1997 ◽  
Vol 70 (3) ◽  
pp. 519-529 ◽  
Author(s):  
J. C. Marmo ◽  
K. B. Wagener
Keyword(s):  
Molecular Weight ◽  
Transition Metal ◽  
Catalytic System ◽  
Lewis Acid ◽  
Catalyst System ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Side Reactions

Abstract The employment of transition metal catalysts has been a viable route in the degradation and depolymerization of unsaturated polymers. Initially, unsaturated polymers were degraded with a catalytic system containing a transition metal and a Lewis acid cocatalyst (WCl6/SnBu4). Degradation chemistry was effective in reducing the molecular weight of the polymer, however, the classical catalyst system induces side reactions which generates ill-defined products. These side reactions were obviated by using a preformed alkylidene without a Lewis acid cocatalyst, and perfectly difunctional telechelics were synthesized.

Hypervalent Iodine-Mediated Beckmann Rearrangement of Ketoximes

Synlett ◽  
2018 ◽  
Vol 29 (11) ◽  
pp. 1465-1468 ◽  
Author(s):  
Tomohiro Maegawa ◽  
Yasuyoshi Miki ◽  
Ryohei Oishi ◽  
Kazutoshi Segi ◽  
Hiromi Hamamoto ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Beckmann Rearrangement ◽  
Hypervalent Iodine ◽  
Mild Conditions ◽  
High Yields

We developed a Beckmann rearrangement employing hypervalent iodine reagent under mild conditions. The reaction of ketoxime with hypervalent iodine afforded the corresponding ketone, but premixing of hypervalent iodine and a Lewis acid was effective for promoting Beckmann rearrangement. Aromatic and aliphatic ketoximes were converted into their corresponding amides in good to high yields.

Gram-scale Preparation of Acyl Fluorides and Their Reactions with Hindered Nucleophiles

Synthesis ◽  
2021 ◽  
Author(s):  
Michał Tryniszewski ◽  
Michal Barbasiewicz
Keyword(s):  
Phase Transfer ◽  
Lithium Amide ◽  
Acyl Chlorides ◽  
Mild Conditions ◽  
Convenient Procedure ◽  
Halogen Exchange ◽  
Scale Preparation ◽  
Biphasic Mixture ◽  
Sterically Hindered

A series of acyl fluorides was synthesized at 100 mmol scale using phase transfer catalyzed halogen exchange between acyl chlorides and aqueous bifluoride solution. The convenient procedure consists of vigorous stirring of the biphasic mixture at rt, followed by extraction and distillation. Isolated acyl fluorides (usually 7 g to 20 g) display excellent purity, and can be transformed into sterically hindered amides and esters, when treated with lithium amide bases and alkoxides under mild conditions.

Polymer characterization

2004 ◽  
Author(s):  
Ian L. Hosier ◽  
Alun S. Vaughan
Keyword(s):  
Molecular Weight ◽  
Electrode Materials ◽  
Polymeric Materials ◽  
Optical Nonlinearity ◽  
Polymer Science ◽  
New Materials ◽  
Wide Range ◽  
Step Growth ◽  
Step Growth Polymerization ◽  
Increasing Demand

Polymer science is, of course, driven by the desire to produce new materials for new applications. The success of materials such as polyethylene, polypropylene, and polystyrene is such that these materials are manufactured on a huge scale and are indeed ubiquitous. There is still a massive drive to understand these materials and improve their properties in order to meet material requirements; however, increasingly polymers are being applied to a wide range of problems, and certainly in terms of developing new materials there is much more emphasis on control. Such control can be control of molecular weight, for example, the production of polymers with a highly narrow molecular weight distribution by anionic polymerization. The control of polymer architecture extends from block copolymers to other novel architectures such as ladder polymers and dendrimers. Cyclic systems can also be prepared, usually these are lower molecular weight systems, although these also might be expected to be the natural consequence of step-growth polymerization at high conversion. Polymers are used in a wide range of applications, as coatings, as adhesives, as engineering and structural materials, for packaging, and for clothing to name a few. A key feature of the success and versatility of these materials is that it is possible to build in properties by careful design of the (largely) organic molecules from which the chains are built up. For example, rigid aromatic molecules can be used to make high-strength fibres, the most highprofile example of this being Kevlar®; rigid molecules of this type are often made by simple step-growth polymerization and offer particular synthetic challenges as outlined in Chapter 4. There is now an increasing demand for highly specialized materials for use in for example optical and electronic applications and polymers have been singled out as having particular potential in this regard. For example, there is considerable interest in the development of polymers with targeted optical properties such as second-order optical nonlinearity, and in conducting polymers as electrode materials, as a route towards supercapacitors and as electroluminescent materials. Polymeric materials can also be used as an electrolyte in the design of compact batteries.

scholarly journals An all solid-state Li ion battery composed of low molecular weight crystalline electrolyte

RSC Advances ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8780-8789 ◽  
Author(s):  
Prerna Joshi ◽  
Raman Vedarajan ◽  
Anjaiah Sheelam ◽  
Kothandaraman Ramanujam ◽  
Bernard Malaman ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Solid State ◽  
Lewis Acid ◽  
Low Molecular Weight ◽  
Li Ion Battery ◽  
Acid Base ◽  
Base Interaction ◽  
Li Ion ◽  
Acid Base Interaction

A non-polymer crystalline organoboron electrolyte results in the formation of nano-channels for directional conduction of Li ions, owing to presence of boron, allowing Lewis acid–base interaction.

scholarly journals Hyperbranched polymers with step-growth chemistries from transfer-dominated branching radical telomerisation (TBRT) of divinyl monomers

2020 ◽  
Vol 11 (48) ◽  
pp. 7637-7649
Author(s):  
Savannah R. Cassin ◽  
Pierre Chambon ◽  
Steve P. Rannard
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Hyperbranched Polymers ◽  
Branched Polymers ◽  
Novel Materials ◽  
Step Growth

The commercially relevant synthesis of novel materials with step-growth backbones has been achieved by applying conventional chemistries to the radical telomerisation of divinyl monomers leading to high molecular weight branched polymers.

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