Coordination-insertion Polymerization
Coordination-insertion Polymerization - Related Videos
06:45
Polymerization
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2023
Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA Polymers are made from macromolecules, which are composed of repeating units (the so called monomeric units). In our modern world, polymers play an important role. One of the first important polymers was nylon, which is a polyamide. It found widespread application in tooth brushes and stockings.
09:08
A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes
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Cited by 5 •
2017
We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.
02:57
Coordination Number and Geometry
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2020
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar. Coordination Number Molecular Geometry Example 2 linear [Ag(NH3)2]+ 3 trigonal planar [Cu(CN)3]2− 4 tetrahedral(d0 or d10), low oxidation...
07:28
Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
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2015
A protocol for the high-throughput analysis of polymerization catalyst, chain transfer polymerizations, polyethylene characterization, and reaction kinetic analysis is presented.
02:54
Coordination Compounds and Nomenclature
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2020
In most main group element compounds, the valence electrons of the isolated atoms combine to form chemical bonds that satisfy the octet rule. For instance, the four valence electrons of carbon overlap with electrons from four hydrogen atoms to form CH4. The one valence electron leaves sodium and adds to the seven valence electrons of chlorine to form the ionic formula unit NaCl (Figure 1a). Transition metals do not normally bond in this fashion. They primarily form coordinate covalent bonds, a...
FAQs
The metal catalyst’s structure determines more than whether polymerization occurs. It can alter the rate at which monomer is incorporated and influence the resulting molecular weight, branching, and stereochemistry. In practice, selecting a catalyst structure allows chemists to tune polymer architecture rather than treating the catalyst as merely a reaction initiator.
Each insertion preserves a reactive metal–carbon chain end, so the growing polymer can undergo another cycle of monomer coordination and insertion. Repetition accounts for chain growth and links molecular events at the catalyst center to macroscopic polymer properties. The balance of these cycles helps determine how far chains extend and what architecture they develop.
Temperature, pressure, and solvent are important process variables because they can change polymerization rate and the properties of the product. Their effects are not independent of monomer identity or catalyst structure. Adjusting these conditions therefore provides a way to influence molecular weight, branching, and stereochemistry while maintaining the same general coordination-insertion sequence.
A typical experimental workflow combines a suitable unsaturated monomer with a transition-metal catalyst under selected temperature, pressure, and solvent conditions. The monomer first coordinates at the metal center, then inserts into the metal–carbon bond. Repeating this sequence extends the chain, after which the resulting polymer can be considered through its molecular weight, branching, stereochemistry, and related properties.
Polyolefin production is a major application, particularly for polyethylene and polypropylene formed from suitable unsaturated monomers. The method is valuable when researchers need to connect catalyst and process choices with polymer architecture, including molecular weight, branching, and stereochemistry. Those structural features can then be used to target mechanical, thermal, and chemical behavior.
In chemistry, stereochemistry is an important outcome to monitor because catalyst structure and operating conditions can influence it along with rate, molecular weight, and branching. Comparing stereochemical differences helps relate changes in the catalytic system or polymerization environment to the resulting polymer. This is relevant when tailoring materials for specific mechanical, thermal, or chemical properties.