Substituent Exchange Reactions with High Polymeric Organophosphazenes

Abstract

Side group exchange reactions have been studied for linear high polymeric organophosphazenes, [N═P(OR2)]n (n ∼ 15 000). Specifically, the exchange behavior of polymers was examined where OR = OCH2CF3, OCH2CF2CF2CF2CF2H, OCH2Cl3, OC6H4CHO-p, OC6H4CN-p, and OC6H4NO2-p with sodium trifluoroethoxide. No aryloxy group replacement by trifluoroethoxy was detected, probably due to the well-protected reactive sites of the polyphosphazenes shielded by aryloxy side groups. For the exchange behavior of [N═P(OCH2CF3)2]n and [N═P(OCH2CF2CF2CF2CF2H)2]n with NaOCH2CF2CF2CF2CF2H and NaOCH2CF3, partial substituent exchange was achieved for both reactions. Furthermore, under conditions with excess nucleophile these side group exchange reactions are followed by reactions that introduce sodium–oxo groups attached to phosphorus in place of organic substituents, and this is a mechanism for subsequent hydrolysis and molecular weight decline in the presence of water. Thus, the relative instability of high polymeric [N═P(OCH2CF3)2...