A polymer is a structure composed of macromolecules. For common names of polymers, the prefix poly is set in roman type, lower case, and solid with the rest of the name, which may or may not be in brackets:
polyacrylamide poly(vinyl chloride) [Poly(vinyl chloride) at the start of a sentence]
Other descriptors are given in lower case and italics (eg graft, blend, co, per):
poly(3-hexylthiophene)-blend-polystyrene poly(styrene-co-isoprene)
IUPAC has a good guide: A brief guide to polymer nomenclature.