Molar Masses, Molecular Weights, and SI Units

The dimensionless quantity relative molecular mass (molecular weight), defined as the average mass of the molecule divided by one twelfth the mass of an atom of the nuclide c, is often used in polymer chemistry and called the molecular weight. In this book, the quantity molar mass is also used and the appropriate SI units are given. 

Determination of the number-average molar mass M involves counting the total number of molecules, regardless of their shape or size, present in a unit mass of the polymer. The methods are converuently grouped into three categories end-group assay, thermodynamic, and transport methods. 

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