Question

Define the weight average molecular masses of a polymer.

Answer 1

If a polymer consists of mass m₁ of macromolecules of molecular mass M₁, mass m₂ of macromolecules of molecular mass M₂, mass m₃ of macromolecules of molecular mass M₃, ......... and so on, the weight average molecular mass, `bar M_W`, is defined as

`bar M_W = (m_1M_1 + m_2M_2 + m_3M_3 + .....)/(m_1 + m_2 + m_3 + .....)`

= `(sum m_i M_i)/(sum m_i)`

Where m_i is the mass of the macromolecules whose molecular mass is M_j.