Phosphonic acid-functionalized polymers
are receiving
much attention
in proton-exchange materials, while phosphonic acid-bearing fluorinated
copolymers are difficult to access for high ion-exchange capacity
(IEC) resins. To overcome the limitation of the lower reactivity ratio
of perfluorinated vinyl ethers, herein, the emulsion copolymerization
of perfluorophosphonate vinyl ether and vinyl acetate was screened
and performed using NaHSO3–Na2S2O8 redox catalysts at 30 °C to produce fluorinated
phosphonate copolymers with a high molecular weight of 220 kDa. These
fluorinated phosphonate copolymers and their alcoholyzed ones with
phosphonic acids exhibit good thermostability of T
d > 270 °C, relative hydrophobicity with water
contact
angle >90°, and a high Young’s modulus >340 MPa
with a
fracture elongation of >40%. Noteworthy is that the fluorinated
copolymer
with 34.7 mol % phosphonate had an IEC of 3.19 mmol/g, which was ∼3-
fold higher than that of commercial Nafion@117. Importantly, this
work provides an efficient, safe, and low-pollution method for the
preparation of phosphonic acid-bearing fluorinated copolymers with
good thermal, mechanical, and high IEC properties, holding potential
applications in solid polymer electrolytes or proton-exchange membranes.