Van der Waals forces only.

There are no permanent dipoles or hydrogen bonds because the polymer chains consist only of non-polar C–C and C–H bonds. Therefore, only weak induced dipole-dipole interactions (Van der Waals forces) exist between the chains.

Hydrogen bonds are the strongest force.

Kevlar contains amide linkages (-CO-NH-). Hydrogen bonds form between the lone pair on the oxygen of one chain and the hydrogen attached to the nitrogen on an adjacent chain. Van der Waals forces are also present but are weaker than the hydrogen bonds.

Hydrogen bonds are the strongest force.

The polymer chain contains hydroxyl (-OH) groups. Hydrogen bonds form between the lone pair on an oxygen atom of one chain and the hydrogen atom of an -OH group on a neighbouring chain. Van der Waals forces are also present.

Hydrogen bonds are the strongest force.

Like Kevlar, Nylon-6,6 is a polyamide. Hydrogen bonds form between the oxygen of the carbonyl group (C=O) and the hydrogen of the amine group (N-H) on adjacent chains. Van der Waals forces also act along the hydrocarbon sections of the chain.

Permanent dipole-dipole interactions.

Terylene is a polyester containing polar C=O and C-O bonds, creating permanent dipoles. However, there are no hydrogen atoms directly bonded to highly electronegative atoms (like N, O, or F) capable of hydrogen bonding. Therefore, no hydrogen bonds form.

Permanent dipole-dipole interactions.

Polylactic acid (PLA) is a polyester. While the monomer (lactic acid) contains an -OH group, this group is lost during the condensation polymerisation process to form the ester link. Consequently, the polymer chain lacks the O-H groups required for hydrogen bonding, relying instead on permanent dipole-dipole attractions between the polar ester groups.