Which material type tends to deteriorate primarily due to dissolution or swelling when exposed to a liquid solvent?

• A. All of the above
• B. Ceramics
• C. Metals
• D. Polymers

Answer: (D)

When a liquid solvent meets a material, the way the material interacts with the solvent determines how it deteriorates. Polymers stand out because their long-chain molecules create free volume that readily allows solvent molecules to diffuse in. This diffusion causes swelling, where the polymer absorbs solvent and expands, softening the material and reducing its mechanical strength. If the solvent interacts strongly enough with the polymer chains, those chains can be pulled apart and the polymer can dissolve into the liquid, leading to loss of mass and integrity. Metals and ceramics, by contrast, tend to degrade mainly through corrosion or chemical attack that removes material or forms surface compounds, rather than swelling or dissolving. So the deterioration mechanism described—dissolving or swelling in a liquid solvent—is most characteristic of polymers.