31.5 Olefin Metathesis Polymerization
2 min read•may 7, 2024
is a powerful tool for making complex polymers. It works by rearranging using metal catalysts, allowing for the creation of diverse polymer structures with useful properties.
This method comes in two main flavors: and . Both use similar catalysts but differ in their starting materials and products. The resulting polymers can be further modified, making them versatile building blocks for various applications.
Olefin Metathesis Polymerization Mechanism and Types
Mechanism of olefin metathesis polymerization
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- Involves rearrangement of carbon-carbon double bonds catalyzed by
- Proceeds through intermediate formed by reaction of metal-alkylidene with olefin monomer
- Metallacyclobutane undergoes retro [2+2] cycloaddition yielding new metal-alkylidene and olefin
- Newly formed metal-alkylidene reacts with another olefin monomer continuing polymerization cycle
- Results in redistribution of carbon-carbon double bonds and formation of polymeric product
ROMP vs ADMET polymerization methods
- ROMP ()
- Polymerizes cyclic olefins (, )
- Driven by release of ring strain
- Produces polymers with double bond in backbone of each repeat unit
- Synthesizes high molecular weight polymers with well-defined structures
- ADMET ()
- Polymerizes linear -dienes
- Produces polymers with double bond at end of each repeat unit
- Requires continuous removal of to drive equilibrium towards polymerization
- Typically yields lower molecular weight polymers compared to ROMP
- Both ROMP and ADMET use same metal-alkylidene catalysts and proceed through metallacyclobutane intermediate
Advantages of olefin metathesis polymerization
- Compatible with wide range of functional groups (esters, ethers, amides)
- Allows incorporation of diverse functionalities into polymer structure
- Resulting polymers contain carbon-carbon double bonds for post-polymerization modification
- Double bonds can be hydrogenated to improve thermal and oxidative stability
- Double bonds can be functionalized via , ,
- Synthesizes various polymer architectures
- Linear polymers, , prepared by controlling monomer feed and catalyst selection
- Conducted under mild conditions
- Many reactions carried out at room temperature or slightly elevated temperatures
- Tolerant to air and moisture depending on specific catalyst used
Catalysts and Polymerization Control
- are essential for
- : ruthenium-based, highly active and tolerant to functional groups
- : molybdenum or tungsten-based, highly active but sensitive to air and moisture
- can be achieved with certain catalyst systems
- Allows for precise control over molecular weight and polymer architecture
- can occur, affecting molecular weight distribution
- Can be controlled through choice of catalyst and reaction conditions
Key Terms to Review (30)
$eta,
u$-dienes: $eta,
u$-dienes are organic compounds that contain two carbon-carbon double bonds, with one at each end of the carbon chain. These types of dienes are particularly important in the context of olefin metathesis polymerization, as they can undergo this reaction to form polymeric structures.
Acyclic Diene Metathesis: Acyclic diene metathesis (ADMET) is a type of olefin metathesis reaction that involves the formation of linear polymers from acyclic dienes. It is a powerful tool in organic synthesis and polymer chemistry, allowing for the efficient construction of complex molecules and the synthesis of specialty polymers.
Acyclic diene metathesis (ADMET): Acyclic Diene Metathesis (ADMET) is a polymerization technique in organic chemistry that involves the reaction of acyclic diene precursors to form polymers through a metathesis mechanism. This process enables the construction of long polymer chains by sequentially adding double bonds between carbon atoms.
ADMET: ADMET is a set of pharmacokinetic properties that describe the absorption, distribution, metabolism, and excretion of a drug molecule in the body. It is a crucial consideration in the development and evaluation of new drug candidates.
Block copolymers: Block copolymers are a type of copolymer where two or more homopolymer subunits are linked together in a linear sequence. They exhibit unique physical properties due to the distinct segments that can microphase separate, leading to materials with diverse functionalities.
Block Copolymers: Block copolymers are a type of copolymer composed of two or more chemically distinct polymer blocks linked together in a linear fashion. They exhibit unique properties and self-assembly behaviors that make them useful in a variety of applications, particularly in the context of copolymerization and olefin metathesis polymerization.
Carbon-Carbon Double Bonds: A carbon-carbon double bond is a covalent chemical bond in which two carbon atoms are connected by two shared pairs of electrons. This type of bond is found in many organic compounds and is particularly important in the context of olefin metathesis polymerization.
Chain Transfer: Chain transfer is a process that can occur during chain-growth polymerization or olefin metathesis polymerization, where the growing polymer chain is terminated and a new chain is initiated. This process involves the transfer of the active center from one polymer chain to another, leading to the formation of polymer chains with varying lengths.
Cyclopentene: Cyclopentene is a cyclic alkene with the molecular formula C₅H₈. It is a key structural component in organic chemistry, with important applications in the context of calculating the degree of unsaturation, olefin metathesis polymerization, and intramolecular olefin metathesis.
Epoxidation: Epoxidation is a chemical reaction that converts alkenes (carbon-carbon double bonds) into cyclic ethers called epoxides. This process involves the addition of an oxygen atom across the double bond, creating a three-membered ring structure. Epoxidation is an important transformation in organic chemistry, with applications in the synthesis of various compounds and the production of polymers.
Ethylene Gas: Ethylene gas, also known as ethene, is a simple unsaturated hydrocarbon with the chemical formula C2H4. It is a colorless, flammable gas that is naturally produced by many plants and plays a crucial role in olefin metathesis polymerization.
Graft copolymers: Graft copolymers are a type of copolymer where one or more species of monomers (side chains) are chemically bonded to the main polymer chain, creating a branched molecular structure. These structures allow for the combination of different polymer properties in a single material.
Graft Copolymers: Graft copolymers are a type of copolymer where one or more polymeric side chains, known as 'grafts', are attached to the main polymer backbone, or 'trunk'. This unique molecular architecture allows for the combination of properties from the different polymer components, making graft copolymers versatile materials with a wide range of applications.
Grubbs Catalysts: Grubbs catalysts are a class of ruthenium-based organometallic complexes that are widely used in olefin metathesis reactions, including olefin metathesis polymerization. These catalysts facilitate the rearrangement of carbon-carbon double bonds, enabling the synthesis of a variety of organic compounds and polymers.
Hydroboration: Hydroboration is a chemical reaction in which a borane compound (BH3) is added to an alkene, resulting in the formation of an organoborane intermediate. This reaction is a key step in the hydroboration-oxidation process, which is widely used in organic synthesis for the selective anti-Markovnikov addition of alcohols to alkenes.
Living Polymerization: Living polymerization is a type of chain-growth polymerization where the active center of the polymer chain remains intact and continues to propagate the chain growth, resulting in the formation of well-defined polymeric structures with controlled molecular weight and narrow molecular weight distribution.
Metal-Alkylidene Complex: A metal-alkylidene complex is a type of organometallic compound where a metal center is bonded to a carbon-based ligand known as an alkylidene. These complexes play a crucial role in olefin metathesis polymerization reactions, which involve the rearrangement of carbon-carbon double bonds.
Metallacycle: A metallacycle is a cyclic compound that features a metal atom incorporated into the ring structure. It plays a crucial role in olefin metathesis polymerization by facilitating the exchange of substituents between olefins, leading to the formation of polymers.
Metallacyclobutane: A metallacyclobutane is a cyclic organic compound containing a metal atom as part of the ring structure. It is a key intermediate in olefin metathesis reactions, which are important for the synthesis of new carbon-carbon bonds and the formation of polymers.
Norbornene: Norbornene, also known as bicyclo[2.2.1]hept-2-ene, is a cyclic alkene compound that is commonly used in organic chemistry, particularly in the context of the Diels-Alder reaction and olefin metathesis polymerization. It is a strained, bicyclic hydrocarbon with a rigid structure that exhibits unique reactivity and applications.
Olefin metathesis polymerization: Olefin metathesis polymerization is a chemical reaction that transforms olefins, which are unsaturated hydrocarbons containing carbon-carbon double bonds, into polymers through the exchange of alkylene groups. This process relies on catalysts to break and reform the double bonds in a way that creates long polymer chains.
Olefin Metathesis Polymerization: Olefin metathesis polymerization is a type of step-growth polymerization reaction where cyclic or acyclic alkene (olefin) monomers undergo a catalytic rearrangement to form new carbon-carbon double bonds, leading to the formation of polymeric chains.
Olefin metathesis reaction: An olefin metathesis reaction is a chemical process that involves the exchange of alkene (olefin) fragments by the breaking and reformation of carbon-carbon double bonds. It is widely used in the synthesis of polymers, pharmaceuticals, and petrochemicals.
Ring-Opening Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP) is a type of olefin metathesis reaction that involves the polymerization of cyclic olefins. This process opens up the cyclic structure and forms a linear polymer chain through the rearrangement of carbon-carbon double bonds.
Ring-opening metathesis polymerization (ROMP): Ring-opening metathesis polymerization (ROMP) is a type of polymerization process that involves the opening of cyclic olefins (ring molecules) and their transformation into linear polymers through the use of specific catalysts. This method allows for the creation of polymers with tailored properties by controlling the structure of the starting material.
ROMP: ROMP, or Ring-Opening Metathesis Polymerization, is a type of olefin metathesis reaction used to create polymeric materials. It involves the opening of cyclic olefins to form linear polymers through the rearrangement of carbon-carbon double bonds.
Schrock Catalysts: Schrock catalysts are a class of molybdenum-based organometallic compounds used as catalysts in olefin metathesis reactions. They are known for their high activity and selectivity in these transformations, making them valuable tools in organic synthesis.
Sharpless epoxidation: Sharpless epoxidation is a chemical reaction that selectively transforms primary and secondary allylic alcohols into their corresponding epoxy alcohols using titanium tetraisopropoxide, tert-butyl hydroperoxide, and diethyl tartrate. It is noteworthy for its stereospecificity, predominantly producing molecules with a specific three-dimensional arrangement.
Thiol-Ene Addition: Thiol-ene addition is a type of click chemistry reaction that involves the addition of a thiol (R-SH) to an alkene or olefin (R'-CH=CH2) to form a new carbon-sulfur bond. This reaction is widely used in organic synthesis, polymer chemistry, and materials science due to its high efficiency, selectivity, and tolerance to various functional groups.
Transition Metal Catalysts: Transition metal catalysts are a class of organometallic compounds that facilitate chemical reactions by providing an alternative pathway with lower activation energy. They are widely used in various organic transformations, including olefin metathesis polymerization.