How is the strength of a polymer determined?

The strength of a polymer is determined by its molecular structure and the type of intermolecular forces present.

The strength of a polymer is fundamentally determined by its molecular structure, which includes the arrangement of its atoms and the type of bonds between them. Polymers are large molecules made up of repeating subunits called monomers. The way these monomers are arranged and bonded together can greatly influence the strength of the polymer.

Polymers can be classified into two main types based on their structure: addition polymers and condensation polymers. Addition polymers are formed by the addition of monomers with unsaturated bonds, resulting in a long chain molecule. These polymers tend to be strong and rigid due to the strong covalent bonds between the atoms. On the other hand, condensation polymers are formed by the elimination of a small molecule, such as water, during polymerisation. These polymers are usually less strong and more flexible.

The type of intermolecular forces present in a polymer also plays a crucial role in determining its strength. There are three main types of intermolecular forces: dispersion forces, dipole-dipole interactions, and hydrogen bonding. Dispersion forces are the weakest and are present in all polymers. Dipole-dipole interactions are stronger and occur in polymers where the monomers have a permanent dipole moment. Hydrogen bonding is the strongest and occurs in polymers containing hydrogen bonded to a highly electronegative atom, such as oxygen or nitrogen.

In general, the stronger the intermolecular forces, the stronger the polymer. This is because stronger intermolecular forces require more energy to break, making the polymer more resistant to deformation and breakage. Therefore, polymers with hydrogen bonding are typically stronger than those with only dispersion forces or dipole-dipole interactions. However, other factors, such as the degree of polymerisation and the presence of cross-linking, can also affect the strength of a polymer.