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While this does create a radical on the affected monomer, resonance stabilization of this radical discourages further propagation (Figure 20). [2] Figure 20: Chain transfer from polypropylene to monomer. To initiator: a polymer chain reacts with an initiator, which terminates that polymer chain, but creates a new radical initiator (Figure 21 ...
In chemistry, chain propagation (sometimes just referred to as propagation) is a process in which a reactive intermediate is continuously regenerated during the course of a chemical chain reaction. For example, in the chlorination of methane , there is a two-step propagation cycle involving as chain carriers a chlorine atom and a methyl radical ...
Propagation: Propagating radical chains of length n in their active (radical) form, P n •, add to monomer, M, to form longer propagating radicals, P n+1 •. RAFT pre-equilibrium: A polymeric radical with n monomer units (P n ) reacts with the RAFT agent to form a RAFT adduct radical.
Chain propagation (two steps) A radical abstracts a hydrogen atom from methane, leaving a primary methyl radical. The methyl radical then abstracts Cl • from Cl 2 to give the desired product and another chlorine radical. Methane chlorination: propagation The radical will then participate in another propagation reaction: the radical chain.
Chain initiation is the initial generation of a chain carrier, which is an intermediate such as a radical or an ion which can continue the reaction by chain propagation. Initiation steps are classified according to the way that energy is provided: thermal initiation, high energy initiation, and chemical initiation, etc. Thermal initiation uses ...
Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed ...
The expression ‘controlled polymerization’ is sometimes used to describe a radical or ionic polymerization in which reversible-deactivation of the chain carriers is an essential component of the mechanism and interrupts the propagation that secures control of one or more kinetic features of the polymerization or one or more structural ...
RAFT is a degenerative chain transfer process and is free radical in nature. RAFT agents contain di- or tri-thiocarbonyl groups, and it is the reaction with an initiator, usually AIBN, that creates a propagating chain or polymer radical. This polymer chain then adds to the C=S and leads to the formation of a stabilized radical intermediate.