If the PDI of a polymer is 1 it means all the polymer chains are of same molecular weight. an ideal case. What does it mean if the PDI of the polymer is 2? is it possible?
PDI means polydispersity index. In polymer language this usually refers to ratio of weight average molecular weight (Mw) to number average (Mn) sometimes also called as molecular weight distribution. PDI is used to indicate distribution of polymer chain molecular weights in a given polymer. PDI can be obtained by various means: GPC, Rheology , solution viscosity, membrane osmosis (van't Hoff eq.), light scattering (Zimm plot) etc. Keep in mind that there may not be an agreement of PDI values obtained by various techniques as they all use different principles to measure them. A PDI =1 indicates polymer chain to be monodisperse. But, normally it is difficult to synthesizes polymer chains of identical Mw or Mn. therefore, all polymers will have PDI > 1. Usually radical polymerized systems have very narrow mol wt. distribution and will have PDI ~ 1.2 to 1.5. Most polymers have broad distribution which helps in processing a polymer in extruder. narrow PDI polymers are difficult to process as shear thinning is nominal.
Hope this helps...
Dear Narasimha,
If PDI is more than 1 i.e. polymer has extra chains as compare to actual molecular chain. It may be transesterification (like cyclic oligomers) or chain transfer products.
If PDI is 2 means polymer growth is not in a controlled manner and oligomers concentration are more.
it means that your weight averaged molecular mass has two times the value of the number averaged molecular mass.
PDI=Mw/Mn
This implies that you have some high weight polymer chains in the overall mixture which have a big influence on Mw.
Simply, as the PDI value increases the heterogeneity in cross-linking, network formation, chain length, branching, hyper branching will be more with more random arrangement..........
It means that monomers are fully used in the formation of polymers with different size distribution.
PDI means polydispersity index. In polymer language this usually refers to ratio of weight average molecular weight (Mw) to number average (Mn) sometimes also called as molecular weight distribution. PDI is used to indicate distribution of polymer chain molecular weights in a given polymer. PDI can be obtained by various means: GPC, Rheology , solution viscosity, membrane osmosis (van't Hoff eq.), light scattering (Zimm plot) etc. Keep in mind that there may not be an agreement of PDI values obtained by various techniques as they all use different principles to measure them. A PDI =1 indicates polymer chain to be monodisperse. But, normally it is difficult to synthesizes polymer chains of identical Mw or Mn. therefore, all polymers will have PDI > 1. Usually radical polymerized systems have very narrow mol wt. distribution and will have PDI ~ 1.2 to 1.5. Most polymers have broad distribution which helps in processing a polymer in extruder. narrow PDI polymers are difficult to process as shear thinning is nominal.
Hope this helps...
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