Which of the following polymers is known for its low density?

Low density poly(ethene) is known for its low density due to its highly branched molecular structure. This structure leads to a less compact arrangement of polymer chains compared to high density polyethylene, which has a more linear structure that allows for tighter packing of molecules. The increased degree of branching in low density poly(ethene) creates spaces between the chains, resulting in a lower overall density. This characteristic contributes to its flexibility and makes it suitable for a variety of applications such as plastic bags, packaging films, and various containers.

In contrast, high density poly(ethene) is denser because of its greater molecular alignment and packing efficiency. Polyvinyl chloride and polypropylene also possess different structural characteristics that do not align with the low density attribute.