What is an advantage of a cross-linked polymer?

A cross-linked polymer is a polymer in which the long chains of molecules are interconnected or "cross-linked" with one another. This cross-linking offers several advantages, one of which is improving fluid resistance. When polymers are cross-linked, their structure becomes more rigid and stable, making them less permeable to liquids. This characteristic is particularly beneficial in various applications where resistance to solvents, oils, and other fluids is necessary, for instance, in coatings, adhesives, and seals.

The increased rigidity associated with cross-linking helps maintain the integrity of the material in the presence of fluids, preventing degradation or breakdown over time. In contrast, other options present drawbacks associated with polymers that are not cross-linked, such as increased brittleness, decreased strength, or reduced extensibility, which are not advantages of cross-linking.