The Controlled and Regioselective Macromolecular Nitration of Poly(2,2′-dioxy-1,1′-biphenylphosphazene) in Concentrated Sulfuric Acid

• Published in: Macromolecules 2008-10, Vol.41 (19), p.6972-6976
• Main Authors: Carriedo, Gabino A, Presa-Soto, Alejandro, Valenzuela, Maria L
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical modifications; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma801150u

The polyphosphazene [NP(O2C12H8)] n (1) [(O2C12H8) = 2,2′-dioxy-1,1′-biphenyl] was reacted with different molar ratios of 65% aqueous HNO3 (or with LiNO3) in concentrated (98%) sulfuric acid under different experimental conditions to give the nitrated polymers 5,5′-3,3′-{NP[O2C12H8−x (NO2) x ]} n (2) (x = 0.2 to 2) opening the route to further functionalization of (1) directly in the dioxy-biphenyl-phosphorus cyclic units. The reaction was not perfectly randomized and was not regiospecific but showed high regioselectivity in favor of the 5,5′ positions. The glass transitions of the products (in the range 161−238 °C) showed a linear dependence with the NO2 contents evidencing the lack of chemical regularity along the chains. The TGA thermograms of the nitrated polymers showed that the decompositions were faster the higher the NO2 contents leaving less final residue at 800 °C, demonstrating the destabilizing effects of the NO2 on the polyphosphazene. Various attempts to reduce the NO2 groups to NH2 are also described.