Chemical Properties :
The intermolecular forces could affect by dipoles in the monomer units. Polymers including amide or carbonyl groups can form hydrogen bonds between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to the partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, result in the high tensile strength and melting point of polymers containing urethane or urea linkages. Polyesters have dipole-dipole bonding between hydrogen atoms in H-C groups the oxygen atoms in C=O groups . Dipole bonding is weaker than hydrogen bonding, so a polyester's melting point and strength are lower than Kevlar's (Twaron), flexibility is one of the polyesters characteristics .
Ethane, has no permanent dipole. The attractive forces between polyethylene chains arise from weak van der Waals forces. Molecules could imagine as being surrounded by a cloud of negative electrons. As two polymer chains get closer, their electron clouds reject one another. This may cause of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to attract the second polymer chain.