polymethylene

from The Century Dictionary.

• noun A cyclic compound containing three or more methylene groups. The most important are the naphthenes or derivatives of hexamethylene or hexahydrobenzene.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun obsolete (chemistry) Any organic compound having a general formula (CH2)n
• noun chemistry (in combination) Any of many organic compounds either having a polymeric structure of repeating -CH2- groups