what are the factors which will be effected by different solvents in free radical polymerization?
The links below show exemplarily the influence of solvents on radical polymerization. Polar monomers are often more reactive in polar solvents. Initiators, like azo initiators (AIBN) shows often a lower decoposition temperature in polar solvents. The main effect of the solvent is the chain transfer. From solvents with a high chain transfer rate radicals of the initiator or of the monomer can abstract hydrogen, so that a radical of the solvent is form. This radical leads to chain stopping reactions in polymerization and leads to a lower molecular weight of the resulting polymer. Sometimes this effect is desired, sometimes not. Solvents with a high chain transfer effect are alkylated benzenes, halogenated aliphatic hydrocarbons (especially tetrachloro methane or chloroform), THF, diisopropyl ether or isopropanol. Solvents with a low chain transfer effect are benzene, water, chlorobenzene, methyl-tert-butyl ether or tert-butanol (good if high molecular weight is desired).
http://pubs.rsc.org/en/content/articlepdf/1957/TF/TF9575300240
http://onlinelibrary.wiley.com/doi/10.1002/pi.2856/abstract
http://pubs.acs.org/doi/pdf/10.1021/ma00120a002
The links below show exemplarily the influence of solvents on radical polymerization. Polar monomers are often more reactive in polar solvents. Initiators, like azo initiators (AIBN) shows often a lower decoposition temperature in polar solvents. The main effect of the solvent is the chain transfer. From solvents with a high chain transfer rate radicals of the initiator or of the monomer can abstract hydrogen, so that a radical of the solvent is form. This radical leads to chain stopping reactions in polymerization and leads to a lower molecular weight of the resulting polymer. Sometimes this effect is desired, sometimes not. Solvents with a high chain transfer effect are alkylated benzenes, halogenated aliphatic hydrocarbons (especially tetrachloro methane or chloroform), THF, diisopropyl ether or isopropanol. Solvents with a low chain transfer effect are benzene, water, chlorobenzene, methyl-tert-butyl ether or tert-butanol (good if high molecular weight is desired).
http://pubs.rsc.org/en/content/articlepdf/1957/TF/TF9575300240
http://onlinelibrary.wiley.com/doi/10.1002/pi.2856/abstract
http://pubs.acs.org/doi/pdf/10.1021/ma00120a002
In general, the use of solvent in free radical polymerization is to increase the solubility formed polymer chain and 2) increase the heat transfer in the reaction system to make sure the polymerization is more "uniform" compared to the bulk polymerization regarding the molecular weight distribution. Normally, solvents used should be inert and not a part of the reaction.
Thank you for your reply Mr.Long...by using different solvents for polymerization does that effects the molecular weight?
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