Which statement describes network polymers?

• A. Multifunctional monomers forming three-dimensional networks
• B. Linear chains with no cross-linking
• C. Polymers composed only of monomers with two reactive sites
• D. Cross-links formed exclusively by reversible bonds

Answer: (A)

Network polymers arise when monomers have multiple reactive sites and link together to form a connected three-dimensional network. Because each multifunctional monomer can bond to several others, the chains become interlinked into a continuous network that spans the material. This crosslinked structure makes the polymer insoluble and infusible in most solvents and gives high rigidity and thermal resistance.

If monomers only have two reactive sites, you mainly get linear chains with little or no crosslinking, so the material wouldn’t be a true network. Describing cross-links as formed exclusively by reversible bonds is too restrictive, since many network polymers rely on permanent (or non-reversible) covalent crosslinks.