Interpretation of chromatogram

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SUMMARY

This discussion focuses on the determination of Number Average Molecular Weight (Mn) and Weight Average Molecular Weight (Mw) of polystyrene samples using Gel Permeation Chromatography (GPC). The first sample, prepared by radical polymerization, exhibits a broad weight distribution, while the second sample, a polystyrene-block-isoprene copolymer synthesized via anionic polymerization, shows an additional peak indicative of copolymer presence. The Polydispersity Index (PDI) is calculated using the equation PDI = Mw/Mn. The discussion highlights the interpretation challenges associated with the GPC elugram, particularly regarding the small peak related to copolymer synthesis.

PREREQUISITES
  • Understanding of Gel Permeation Chromatography (GPC)
  • Knowledge of polymer synthesis methods, specifically radical and anionic polymerization
  • Familiarity with molecular weight calculations and the significance of PDI
  • Ability to interpret chromatograms and elugrams
NEXT STEPS
  • Research the principles of Gel Permeation Chromatography (GPC) in detail
  • Explore the effects of polymerization methods on molecular weight distribution
  • Learn about the significance of peaks in GPC elugrams and their relation to copolymerization
  • Investigate advanced techniques for analyzing polymer molecular weights
USEFUL FOR

This discussion is beneficial for polymer chemists, laboratory technicians, and researchers involved in polymer synthesis and characterization, particularly those working with GPC analysis and molecular weight determination.

selseg
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In my polychemistry laboratory , the task was to determine the Number Average Molecular Weight and the Weight Average Molecular weight of two samples , one a polystyrene sample prepared by radical polymerization , and the other a polystyrene-block-isoprene polymer prepared by anionic polymerization.Using Gel Permeation Chromatography . The GPC software generated an elugram and a weight distribution for each sample.

Homework Equations


PDI = Mw/Mn[/B]
This is the link to the plot https://docs.google.com/file/d/0Bw0SjzcEyj3GeTBIZ1NLanJuOWs/edit?pli=1 https://docs.google.com/file/d/0Bw0SjzcEyj3GeTBIZ1NLanJuOWs/edit?pli=1

The Attempt at a Solution


The plot for the first sample is easy to inteprete since it has a broad distribution .The plot for the second has another small peak to the right of the main peak , which I understand is the Copolymer .However I don't understand how that peak came about in relation to synthesis and Molecular Weight [/B]
 
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Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?