Generally

polymer is an insulator due to that polymer chain connected by the covalent single bond does not contain free electrons (carriers). In addition

macromolecular chains are coherent with each other through Van der Waals forces

and hence have large distance between them resulting in poor electron clouds overlapping

so that it is much difficult for carriers’ delocalization. Likewise

polymer even with

π

-bond and conductive electrons

such as polyacetylene

is nonconductive as well. The reason is the one-dimensional chain structure in which Peierls instability occurs.