In chemistry|lang=en terms the difference between polymeric and pentaphosphate

is that polymeric is (chemistry) of, relating to, or consisting of a polymer examples of such compounds include polyurethane foams, pvc foams, and styrofoam while pentaphosphate is (chemistry) a polymeric anion composed of five linked phosphate groups; any salt containing this anion.

As an adjective polymeric

is (chemistry) of, relating to, or consisting of a polymer examples of such compounds include polyurethane foams, pvc foams, and styrofoam.

As a noun pentaphosphate is

(chemistry) a compound having five phosphate groups.