CHEM 4214 Lecture Notes - Lecture 3: Molar Mass Distribution, Molecular Mass, Repeat Unit
Document Summary
Pi probability ex: i = 10000 i = # repeat units in polymer. Total # molecules = mole fraction of i-mer: (number) weight fraction of i-mer. Generally, n = 1 --> mn n = 2 --> mw n = 3 --> mz these are 1st-3rd moments of distribution knowing all moments is equivalent to knowing entire distribution of sample. Dispersity (polydispersity index) only equal to 1 when we have 1 m. How to measure mn and mw: absolute measurement. Does not rely on calibration against other techniques: colligative properties: depends on # of solute molecules in the solvent ex: osmotic pressure. End group of polymers have different chemical structures. Chem4212 polymers page 3 laser ga sphase polymer (ion, comes from salt) Biased towards small molecules (easier to ionize smaller polymers) Unknown how much charge got into polymermight not distribute as well. Hard to compare samples (can"t compare one batch with another)
