Dunno Rich ...it's seems a bit of an oddball really. It seems to be highly rated by US bass fishermen and the only negative comment I've found is from one reviewer who said it was 'a bit stretchy', which could lead you to believe that it's most probably not a pre-stretched mono. But maybe that guy usually used only braid and was comparing it to that. It's described 'merely' as a "co-polymer" so presumably it's not fluorocarbon coated.
For a mono it's mid-high priced at ~£36/900m, so the claims for it are either just bull (i.e. a line that only gets bought once as it's found to be "nothing special") or it is a really good blend of monomers and polymers. They say that the copolymer is "patented" so???. I did study polymer chemistry but only to diploma level, and I did spent years in and out of a polymer plant, but that was dealing mostly with acrylics. But from that I do know that in polymer chemistry there
are 'sweet spots' (basically really good 'recipes') e.g. the topcoat on Rolls Royce cars was the same as on Vauxhalls).
I do know for certain that since Dupont came out with Nylon 66 in 1927 there's been some excellent iterations of nylon as copolymers, including some of those used in copolymer fishing lines. That is, lines that stand out from the rest. For example Silstar Match Team line, which is quite an oddball (IMO) and makes a great hooklink, if you can get the know perfect
So there are 'sweet spots', and I guess there's only one sure way to find out whether or not they've found one in 'Polyflex'.
Dunno, I'll buy some eh, and get back to y'all.