What is initiator efficiency?
Initiator efficiency f is defined as the fraction of primary (initiator-derived) free-radical species that add to monomer molecules. The primary fragments from DTBP decomposition cannot undergo cross-disproportionation, as hydrogen atoms in β-position to the oxygen-centered free-radical site are not available.
What is initiator used for?
initiator, a source of any chemical species that reacts with a monomer (single molecule that can form chemical bonds) to form an intermediate compound capable of linking successively with a large number of other monomers into a polymeric compound.
What is initiator efficiency in chain initiation step of free radical polymerization?
2. What is the initiator efficiency in chain initiation step of free radical polymerization? Explanation: the initiator efficiency is the fraction of free radicals actually contributing in chain initiation and is less than unity.
Which is the most useful approach for evaluating initiator efficiency?
Which is the most useful approach for evaluating initiator efficiency? Explanation: This technique allows treating the kinetic data obtained under dead-end conditions to evaluate both kd, the rate constant of initiator decomposition reaction and f, the initiator efficiency, which is most useful of all the approaches.
What is the role of initiator in chain growth polymerization?
Usually an initiator compound reacts with the monomer to start the reaction, and the mechanism of chain polymerization consists of three phases, called initiation, propagation, and termination.
Which of the following factors does initiator efficiency depends on?
Which of the following factors does initiator efficiency depend on? Explanation: The initiator efficiency not only depends on initiator molecules but is also affected by condition of polymerization and the solvent used.
Which of the following can be used as an initiator for the formation of low density polyethylene?
4. Which of the following can be used as an initiator for the formation of low density polyethylene (LDPE)? Explanation: The initiators than can be used for formation of LDPE are peroxides , oxygen or azo-compounds. 5.
What is polymerization initiator?
Polymerization initiators are a source of any chemical species that reacts with a monomer to form an intermediate compound which is capable of linking successively with a large number of other monomers into a polymeric compound.
Why is initiator necessary in free radical polymerization?
Initiation. Initiation is the first step of the polymerization process. Not all monomers are susceptible to all types of initiators. Radical initiation works best on the carbon–carbon double bond of vinyl monomers and the carbon–oxygen double bond in aldehydes and ketones.
What is the initiator in ATRP polymerization?
In all of the published literature on ATRP this R-X molecule has been called the initiator, even though in contrast to standard free radical polymerization initiators, this molecule is an inherently thermally stable entity and is incorporated in its entirety into the final polymer.
What are the catalysts used in ATRP?
Various initiators and catalysts have been used in carrying out ATRP. p -Toluenesulfonyl chloride (TsCl) has been widely used since it is a ‘universal’ initiator capable of initiating a variety of different monomers [10].
What are the advantages of a normal ATRP initiation?
The primary advantage of a ” normal ATRP initiation ” procedure is that it provides great freedom for the choice of both initiator and catalyst complex. The most active catalyst can be selected (provided all reagents are pure and oxygen free) resulting in lower levels of transition metal and other impurities in the final product.
What does ATRP stand for?
Atom Transfer Radical Polymerization (ATRP) ATRP is mechanistically related to transition metal mediated atom transfer radical addition (ATRA) reactions(1) and indeed this relationship was the reason this transition metal mediated controlled radical polymerization process was named ATRP.(2) ATRP can be viewed as a very special case of ATRA.
