Okay, so that history Imipolex G really confused me. I had to ask my science major roommate to explain a lot of the terms Pynchon threw out there. One of the first things I immediately looked up was the word "aromatic." On page 252, Pynchon writes that the Imipolex G is "an aromatic heterocyclic polymer." I didn't know why a type of plastic would produce a fragrant odor, so I looked it up on the OED. Here it is (shortened considerably, since it was very long):

2. Chem. Epithet of an extensive group of organic compounds, consisting of benzene and its homologues In mod. use, pertaining to or designating a compound with one or more planar conjugated rings of the form typified by the benzene molecule; a group of six pi-electrons in the ring of an aromatic molecule regarded as responsible for its aromaticity.