How is poly(vinylphosphonic acid) (PVPA) prepared from vinylphosphonic acid (VPA)?

The polymerizations were performed, if not other wise indicated, with 40 wt.-% solutions of VPA in ethyl acetate or in acetic anhydride containing 2 mol-% AIBN as initiator. The glass ampoules (diameter 18 mm, volume 13 mL) were filled with 4–7mL of reaction solution. After degassingby freeze-pump-thaw cycles, the ampoules were sealed off and stored at -15℃ until the beginning of the experiment. The reaction mixture was reacted at 60℃ for different reaction times up to 8 h and at 35℃ up to 63h. The precipitated polymer was washed with acetic acid and filtered. For reprecipitations, a 20 wt.-% polymer solution in water was titrated with acetic acid until the cloud point (water:acetic acid 1:1, v/v). Then, few drops of water were added to obtain a clear solution again. Subsequently, the polymer was precipitated in a fourfold volume of acetic acid. The solid was isolated by filtration or centrifugation (24000 g) and dried at 608C in a vacuum oven.

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