Of these three, Van der Waals forces, often called electrostatic forces, are the weakest, approximately 6kJ/mol. These occur between all molecules, and since polymer molecules are huge, these forces are significant.

Dipole interactions happen when polar molecules are involved. They tend to be stronger than Van der Waals forces, approximately 10 kJ.mol. In polymers, we find dipoles when a highly electronegative atom is bonded to carbon. Examples are:

C-Cl

C-F

C=O or C-O-C

Hydrogen bonding is a type of dipole interaction. It involves hydrogen and strongly electronegative elements like oxygen, fluorine and nitrogen. These are the strongest type of secondary bonding forces. Examples are

C-OH N-H