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] n in the presence of excess NaOCH2CF3 emerged as an explanation for problems with the synthesis of [NP(OCH2CF3)2] n and [NP(OCH2CF3) x (OCH2(CF2) m CF2H)2–x ] n , polymers that have attracted wide fundamental and practical interest. However, substituent exchange reactions do appear to be an alternative synthetic approach for the synthesis of some polyphosphazenes, especially mixed-substituted elastomers and the recently reported trichloroethoxy/trifluoroethoxy-containing cosubstituted polyphosphazenes.

Limits to expanding the PN‐F series of polyphosphazene elastomers

“…The modest molecular weights and yields of Polymers 2, 3, and 5 are a consequence of the excess amounts of sodium trifluoroethoxide required in the last step. It is known that this condition leads to backbone cleavage [20]. Polymers 2, 3, and 5 are adhesive gums rather than rubbery elastomers.…”

Phosphazene High Polymers and Models with Cyclic Aliphatic Side Groups: New Structure–Property Relationships

“…The sequence utilized in this work yielded a side group ratio close to the targeted value and also gave higher molecular weight polymers. 26 Another important aspect of this synthetic technique is that at the solution concentrations chosen for substitution reactions gelation of the reaction mixture can occur during the initial stage of a reaction. This is due to the highly polar nature of the sodium trifluoroethoxide reagent, which raises the overall polarity of the reaction medium to the point that less polar polymers begin to precipitate at an early stage of the process.…”

Polyphosphazenes with Immobilized Dyes as Potential Color Filter Materials

“…The amount of the sodium salt of the dye was in excess of the target amount to compensate for the displacement of some dye by C 6 H 5 O − or CH 3 OC 6 H 4 O − . 15 In the following molecular formula of polymers 9−11, OPR represents the deprotonated compound 1 as the side chain, OTPP represents the deprotonated compound 2 as the side chain, OPh represents the deprotonated C 6 H 5 OH as the side chain, OPhOCH 3 represents the deprotonated CH 3 OC 6 H 4 OH as the side chain, and OTFE represents the deprotonated HOCH 2 CF 3 as the side chain.…”

“…The amount of the sodium salt of the dye was in excess of the target loading to compensate for the subsequent displacement of some dye by cyclopenanoxide. 15 A total of 0.29 g of red polymer was collected as the product. Yield 26%.…”