Radical Chain (Addition) Polymerization
The polymerization of unsaturated typically involves a chain reaction. It can be initiated by methods typical for simple gas phase chain reaction, including the action of ultraviolet light. It can susceptible to retardation and inhibition. In a typical chain polymerization, one act of initiation may lead to the polymerization of thousands of monomer molecules.
The characteristics of chain polymerization, suggest that the active center responsible for the growth of the chain is associated with a single polymer molecule through the addition of many monomer units. The polymer molecules are formed from the beginning, and almost no species intermediate between monomer and high molecule weight polymer are found. Of several postulated types of active center, three have been found experimentally, cation, anion, and free radical. Free radical polymerization are described then.
The concept of vinyl polymerization as a chain mechanism is not new, dating back to staudinger's work in 1920. In 1937 Flory showed conclusively the radical polymerization proceed by the requires the steps of initiation, propagation, and termination proceed by and requires the step of initiation, propagation, and termination typical of chain reactions in low molecular weight species.
The carbon carbon carbide double bond is, because of its relatively low stability, particularly susceptible to attack by a free radical. The reaction of the double bond with a radical proceed well for compounds of the type CH2=CHx+CXY, called as vinyl polymer. (Monomer in which flourine is substitute for hydrogen may be included in this class).
Not all vinyl monomers yield high polymer as a result of radical polymerization. Aliphatic hydrocarbons other than ethylene polymerize only to oils, and 1,2-disubstituted ethylenes not at all. Among compounds of type CH2=CXY, those in which both groups are larger than CH3 polymerized slowly, if at all, by radical mechanism.
The characteristics of chain polymerization, suggest that the active center responsible for the growth of the chain is associated with a single polymer molecule through the addition of many monomer units. The polymer molecules are formed from the beginning, and almost no species intermediate between monomer and high molecule weight polymer are found. Of several postulated types of active center, three have been found experimentally, cation, anion, and free radical. Free radical polymerization are described then.
The concept of vinyl polymerization as a chain mechanism is not new, dating back to staudinger's work in 1920. In 1937 Flory showed conclusively the radical polymerization proceed by the requires the steps of initiation, propagation, and termination proceed by and requires the step of initiation, propagation, and termination typical of chain reactions in low molecular weight species.
The carbon carbon carbide double bond is, because of its relatively low stability, particularly susceptible to attack by a free radical. The reaction of the double bond with a radical proceed well for compounds of the type CH2=CHx+CXY, called as vinyl polymer. (Monomer in which flourine is substitute for hydrogen may be included in this class).
Not all vinyl monomers yield high polymer as a result of radical polymerization. Aliphatic hydrocarbons other than ethylene polymerize only to oils, and 1,2-disubstituted ethylenes not at all. Among compounds of type CH2=CXY, those in which both groups are larger than CH3 polymerized slowly, if at all, by radical mechanism.
