Polymer Molecular Mass Averages

These flashcards cover key concepts related to Polymer Molecular Mass Averages to aid in exam preparation.

Polymers are nearly always a mixture of macromolecules of different molar masses, represented as __.

Mi

The amount of macromolecules in a polymer is expressed by the number of molecules (Ni) or by the weight of the macromolecules (Wi = __).

NiMi

In a polymer sample, the molar mass of the repeating unit is __ g/mol.

100

The weight (Wi) of macromolecules is calculated using the formula __.

Wi = NiMi

The number of repeat units in the polymer can range from 1 to __.

5

For a polymer with 5 macromolecules, the total number of repeat units is __.

15

The number average molecular mass (Mn) is defined as __.

Mn = ΣNiMi / ΣNi

The weight average molecular mass (Mw) is calculated using __.

Mw = ΣWiMi / ΣWi

When all macromolecules are the same mass, Mn = Mw; however, for polymers, it is generally true that __.

Mn < Mw

The ratio of Mw/Mn is known as __ and characterizes the breadth of the molecular mass distribution.

dispersity (Ð)

Polymers are nearly always a mixture of macromolecules of different molar masses, represented as __.

Mi

The amount of macromolecules in a polymer is expressed by the number of molecules (Ni) or by the weight of the macromolecules (Wi = __).

NiMi

In a polymer sample, the molar mass of the repeating unit is __ g/mol.

100

The weight (Wi) of macromolecules is calculated using the formula __.

Wi = NiMi

The number of repeat units in the polymer can range from 1 to __.

5

For a polymer with 5 macromolecules, the total number of repeat units is __.

15

The number average molecular mass (Mn) is defined as __.

Mn = ΣNiMi / ΣNi

The weight average molecular mass (Mw) is calculated using __.

Mw = ΣWiMi / ΣWi

When all macromolecules are the same mass, Mn = Mw; however, for polymers, it is generally true that __.

Mn < Mw

The ratio of Mw/Mn is known as __ and characterizes the breadth of the molecular mass distribution.

dispersity (Ð)

What does a dispersity value equal to 1 (Ð = 1) indicate about a polymer sample?

It indicates that all macromolecules in the polymer sample have the exact same molar mass (monodisperse).

The statistical distribution of molecular masses in a polymer sample is primarily a result of __.

the inherent randomness and varying reaction rates during polymerization processes