For most industrial purposes, degrees of polymerization in the thousands or tens of thousands are desired. This number does not reflect the variation in molecule size of the polymer that typically occurs, it only represents the mean number of monomeric units. CO—, so that a chain of 1000 monomeric units corresponds to 500 repeat degree of polymerization pdf. Carothers’ equation does not apply.
Instead long chains are formed from the beginning of the reaction. Long reaction times increase the polymer yield, but have little effect on the average molecular weight. Relationship between degree of polymerization and melting temperature for polyethylene. Polymers with identical composition but different molecular weights may exhibit different physical properties. Synthetic polymers invariably consist of a mixture of macromolecular species with different degrees of polymerization and therefore of different molecular weights. There are different types of average polymer molecular weight, which can be measured in different experiments. Allcock, Lampe and Mark, p.
3548-3553 Melting Points of Linear-Chain Homologs. This page was last edited on 13 August 2017, at 15:11. Addition of each monomer unit regenerates the active site. This type of polymerization result in high molecular weight polymer being formed at low conversion. This final weight is determined by the rate of propagation compared to the rate of individual chain termination, which includes both chain transfer and chain termination steps. This can occur by reaction with the solvent, monomer, or another polymer molecule. Termination, in radical polymerization, is when the free radicals combine and is the end of the polymerization process.
This is most often seen with anionic polymerization as it can be easy to perform without termination steps. 1929, and refers to the type of product produced. Addition polymerization produces only a polymer molecule, while condensation polymerization produces a polymer as well as a molecule with a low molecular weight, usually water. Studies On Polymerization And Ring Formation. An Introduction To The General Theory Of Condensation Polymers”. Cornell University Press, 1953, p.