Molecular weight and carboxyl end group for polyethylene terephthalate

4 Molecular weight (and carboxyl end group for polyethylene terephthalate) 

The Merriam-Webster dictionary defines molecular weight as the average mass of a molecule of a compound compared with one-twelfth the mass of carbon 12 and calculated as the sum of the atomic weights of the constiment atoms. The first known use of molecular weight was in 1869. 

Four types of molecular weight averages are commonly used (Koerner, 2012)  

the z-average molecular weight My, the viscosity average molecular weight 

The different types of molecular weights can be defined in terms of the number of molecules, Nu having molecular weights. A/,-, or their weights, w, with molecular weights Mi. 

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