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Polyphosphazene membranes. III. Solid‐state characterization and properties of sulfonated poly[bis(3‐methylphenoxy)phosphazene]
Author(s) -
Tang Hao,
Pintauro Peter N.,
Guo Qunhui,
O'Connor Sally
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19990118)71:3<387::aid-app4>3.0.co;2-y
Subject(s) - phosphazene , polyphosphazene , crystallinity , membrane , polymer chemistry , polymer , differential scanning calorimetry , materials science , polyelectrolyte , chemical engineering , chemistry , composite material , biochemistry , physics , engineering , thermodynamics
Poly[bis(3‐methylphenoxy)phosphazene] was sulfonated in a solution with SO 3 and solution‐cast into 100–200‐μm‐thick membranes from N,N ‐dimethylacetamide. The degree of polymer sulfonation was easily controlled and water‐insoluble membranes were fabricated with an ion‐exchange capacity (IEC) as high as 2.1 mmol/g. For water‐insoluble polymers, there was no evidence of polyphosphazene degradation during sulfonation. The glass transition temperature varied from −28°C for the base polymer to −10°C for a sulfonated polymer with an IEC of 2.1 mmol/g. The equilibrium water swelling of membranes at 25°C increased from near zero for a 0.04‐mmol/g IEC membrane to 900 % when the IEC was 2.1 mmol/g. When the IEC was < 1.0 mmol/g, SO 3 attacked the methylphenoxy side chains at the para position, whereas sulfonation occurred at all available aromatic carbons for higher ion‐exchange capacities. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized microscopy showed that the base polymer, poly[bis(3‐methylphenoxy)phosphazene], was semicrystalline. For sulfonated polymers with a measurable IEC, the 3‐dimensional crystal structure vanished but a 2‐dimensional ordered phase was retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 387–399, 1999