Pendant cyclodicarbaphosphazatriene-containing monomers and polymers: synthesis, crystal structures and polymerization behavior of [NC(NMe₂)]₂[NP(O-C₆H₄-p-C₆H₄-p-CH=CH₂)(X)], X = Cl, OCH₂CF₃, OC₆H₅, OC₆H₄-m-CH₃, OC₆H₄-p-Br

Abstract

The reaction of the dicarbaphosphazene, [NC(NMe₂)]₂[NPCl₂] (2), with the sodium salt of 4-hydroxy-4'-vinylbiphenyl afforded the vinyl group containing monomer [NC(NMe₂)]₂[NP(Cl)(O-C₆H₄-p-C₆H₄-p-CH=CH₂)] (3). Replacement of the lone chlorine atom of 3 by oxygen nucleophiles gave [NC(NMe₂)]₂[NP(OR)(O-C₆H₄-p-C₆H₄-p-CH=CH₂)] [R = CH₂CF₃ (4); C₆H₅ (5); C₆H₄-m-CH₃ (6); C₆H₄-p-Br(7)]. The X-ray crystal structures of 3-7 reveal that all the cyclodicarbaphosphazenes have a planar N₃PC₂ ring; the ring carbons are completely planar, while the geometry around phosphorus is pseudotetrahedral. The presence of weak intermolecular hydrogen bonding {C-H---X(Cl or Br), C-H---N, or C-H---π } interactions in 3-7 leads to the formation of polymeric architectures in the solid-state. The monomers 4-7 can be polymerized by a free-radical initiator to afford the corresponding air-stable homopolymers 8-11. These have moderate molecular weights with polydispersity indices ranging from 1.33 to 1.58. All of these polymers have high glass transition temperatures and have excellent thermal stability.