Basic Types Of Polymerization Flashcards
A process through which a large number of monomer molecules react together to form a polymer.
Polymerization
IUPAC Definition: A chain reaction in which the growth of a polymer chain proceeds exclusively by reactions between monomer and reactive site on the polymer chain with regeneration of the reactive sites at the end of each growth step.
Chain-growth Polymerization or Addition Polymerization
Chain-growth polymerization involves the addition of ____________ molecules to a rapidly growing chain.
Unsaturated
Enumeration.
Three fundamental steps of Chain-growth Polymerization.
- Initiation
- Propagation
- Termination
Enumeration:
Classification of Chain-growth Polymerization.
- Free radical Polymerization
- Cationic Polymerization
- Anionic Polymerization
- Coordination or Stereoregular Polymerization
IUPAC Definition: A chain polymerization in which the kinetic-chain carriers are free radicals.
Free Radical Polymerization
Most frequently, initiation of free radical polymerization is brought about by the addition of small quantities of compounds called __________.
Initiators
Usually a weak organic compound that can be decomposed thermally or by irradiation to produce free radicals, which are molecules containing atoms with unpaired electrons.
Initiators
Enumeration.
Initiation in a free-radical polymerization consists of two-steps.
- Dissociation
- Addition
It involves the dissociation of a radical initiator molecule which is easily dissociated by heat or light into two free radicals.
Chain Initiation.
Involves the linear growth of the polymer chain by the sequential addition of monomer units to this active growing chain molecule.
Propagation
IUPAC Definition: A reaction of an active center on the growing polymer molecule, which adds one monomer molecule to form a new polymer molecule one repeat unit longer.
Chain Propagation
The sequence of propagation reactions is terminated at some point due to annihilation of the radical center of the propagating chain.
Termination
Enumeration.
Two termination step that involves the reaction of any two free radicals with each other.
- Combination
- Disproportionation
Two propagating chains are terminated when two radicals combine to form an electron-pair (covalent) bond
Combination (Coupling)
The reaction of the unpaired electrons of two chains to form a covalent bond between them.
Combination
This termination step involves two growing molecules that react to from two “dead chains”.
Disproportionation
The transfer of a hydrogen atom from one chain to the other so that the two product chain molecules are unchanged in length but are no longer free radicals.
Disproportionation
A growing polymer chain is deactivated or terminated by transferring its growth activity to a previously inactive species.
Chain Transfer
Involve chain carriers or reactive centers that are organic ions or charged organic groups.
Ionic Polymerization
IUPAC Definition: An ionic polymerization in which the kinetic-chain carriers are cations.
Cationic Polymerization
A type of chain growth polymerization in which a cationic initiator transfers charge to a monomer, which then becomes reactive.
Cationic Polymerization
The catalysts generally require the presence of a Lewis base such as water, alcohol, or acetic acid
Cocatalyst
IUPAC Definition: An ionic polymerization in which the kinetic-chain carriers are anion.
Anionic Polymerization
A form of chain-growth polymerization or addition polymerization that involves polymerization of monomers initiated with anions.
Anionic Polymerization
Enumeration.
Commonly used initiator systems for anionic polymerization.
- Alkali Metals and Alkali Metal Complexes
- Organometallic Compounds
- Lewis Bases
- High-energy Radiation
Initiate polymerization by transfer of an electron to the double bond of the monomer.
Alkali Metals and Alkali Metal Complexes
Initiation by _________ and __________ occurs by a direct attack of these compounds on the double bond of the monomer molecule.
Organometallic Compounds, Lewis Bases
Complexing of the monomer to the initiator frequently precedes the insertion process and this polymerization is therefore often called _______________.
Coordination Polymerization
The range of type of this catalysts was subsequently extended to produce polymers exhibiting a wide range of stereoregular structures including those derived from dienes and cycloalkenes.
Ziegler-Natta Catalysts
It refers to a type of polymerization mechanism which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers.
Step-growth Polymerization
It refers to the molecule’s interlinking capacity or the number of sites it has available for bonding with other molecules under the specific polymerization conditions.
Functionality
In step-growth polymerization, the stepwise reaction occurs between pairs of chemically ____________ on the reacting molecules.
Reactive or Functional Groups
Enumeration.
Categories of Step-growth Polymerization.
- Polycondensation
- Polyaddition
Small molecule is eliminated at each step.
Polycondensation
Monomers react without the elimination of a small molecule.
Polyaddition
It is used as film (mylar) and in bottle applications.
Polyester
Special class of polyesters derived from carbonic acid.
Polycarbonates
Characterized by the presence of amide linkages (-CONH-) on the polymer main chain.
Polyamides
Condensation polymers obtained from the reaction of dianhydrides with diamines.
Polyimides
Families of synthetic heterocycles with a wide range of applications due to their physical and chemical properties.
Polybenzimidazoles and Polybenzoxazoles
A type of polymer that consists of repeating units connected by aromatic linkers, such as benzene rings.
Aromatic Ladder Polymers, Ladder Polymers or Linker Polymers
Employed in the production of aminoplasts and phenoplasts, which are two different but related classes of thermoset polymers.
Formaldehyde Resins
Polymers consisting of monomers joined together by ether linkages (two carbon atoms bonded to an oxygen atom).
Polyethers
Closely related to polyethers in structure and properties and is typically used as electrical insulators and structural parts in the building of engines and vehicles.
Polysulfides
Another family of linear aromatic polymers that are tough, high temperature-resistant engineering thermoplastics.
Polysulfones
True or False.
1. In step-growth, monomers bearing functional groups such as -OH, -COOH, -NH2, -NCO, etc. undergo step polymerization.
2. In chain-growth, monomers with carbon-carbon unsaturation undergo polymerization when an active center is formed.
Both statements are true.
True or False.
1. In step-growth, the growth of polymer molecules proceeds by a stepwise intermolecular reaction, normally with the elimination of small molecules as by-products of condensation. The molecule never stops growing during polymerization.
2. In chain-growth, each polymer molecule/chain increases in size at a rapid rate once it growth has been started by formation of an active center. When the macromolecules stop growing, it can generally not react with more monomers.
Both statements are true.
True or False.
1. In step-growth, any two molecular species present can react.
2. In chain-growth, only growth reaction adds repeating unit two at a time of the chain.
Statement 1 is true.
Statement 2 is false. “Two” -> “One”
True or False.
1. Step-growth: Monomer units can react with each other or with polymers of any size. Growth occurs in a series of fits and starts as the reactive species of a monomer or polymer encounters other species with which it can form a link.
2. Chain-growth: Growth of a polymer molecule is caused by a kinetic chain of reactions involving rapid addition of monomer to an active center that may be a free radical, ion, or polymer-catalyst bond.
Both statements are true.
True or False.
1. Step-growth: This can occur even in the absence of an added catalyst.
2. Chain-growth: The active center is produced by some external source (energy, highly reactive compound, or catalyst)
Both statements are true.
True or False.
1. Step-growth: The average size increases with conversion.
2. Chain-growth: Consists of growing chains of intermediate sizes.
Both statements are true.
True or False.
1. Step-growth: Backbone polymer chains contains heteroatoms such as N, O, S, etc. at a regular intervals due to condensed interunit links.
2. Chain-growth: Usually the backbone of polymer chains consists of -C-C- linkages and other kinds of atoms such as O, N, S, etc. may appear in the side groups.
Both statements are true.
IUPAC Definition: A polymerization in which a cyclic monomer yields a monomeric unit which is acyclic or contains fewer cycles than the monomer.
Ring-opening Polymerization
A form of chain-growth polymerization in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer. The reactive center can be radical, anionic, or cationic.
Ring-opening Polymerization
