Covalent bonds in polymers rupture due to

• A. Swelling and dissolution leading to bond rupture
• B. Oxidation at the surface
• C. Ion exchange
• D. Mechanical wear only

Answer: (A)

The key idea is that covalent bonds along a polymer backbone are broken when the material undergoes chemical degradation and dissolution processes prompted by solvent interaction. When a polymer swells or dissolves in a solvent, solvent molecules diffuse in and separate chains, increasing chain mobility and inducing internal stresses. This environment can promote scission of the covalent bonds because the backbone is exposed to chemical attack (for example, hydrolysis or oxidation) and the mechanical tension from swelling can push bonds beyond their strength. In dissolution, breaking covalent bonds is essentially required to convert long chains into soluble fragments, so bond rupture becomes a direct consequence of the process.

Oxidation at the surface can alter chemistry locally but does not by itself drive widespread rupture of the backbone throughout the material. Ion exchange changes bonded ions without breaking the polymer’s covalent framework. Mechanical wear removes material or reshapes the surface but typically acts on weaker interactions and surface layers rather than causing extensive covalent-bond scission in the bulk.