All of the atoms in a polymer are joined by strong covalent bonds
The intermolecular forces between polymer molecules are larger than simple covalent molecules, so more energy is needed to break them.
The intermolecular forces between polymer molecules are relatively strong, making them solid at room temperatures.
The intermolecular forces in Polymers are weaker than ionic or covalent bonds, making them have lower boiling points than ionic or giant molecular compounds.