Oligo(3,4-ethylenedioxythiophene).

Activated zinc (0.67 g; 10.3 mmol) then 6.6 ml of DMA were mixed with NiBr2bipy (0.063 g; 0.166 mmol), triphenylphosphine (0.52 g; 2 mmol) and 2,5-dibromo-3,4-ethylenedioxythiophene (1 g; 3.3 mmol) under argon atmosphere. The color of the mixture became immediately red and remained unchanged after 2.5 hours under stirring at 95 ‡C. The reaction was allowed to continue for a further hour, then the mixture was poured into 200 ml of sulfuric acid (5%). A black product precipitated and was filtered, washed with distilled water down to neutral pH, 3 times with 50 ml of ether and 3 times with 50 ml of methanol. After drying under vacuum, a black purple powder was obtained in 72% yield. On the contrary to Yamamoto who obtained no residual halogen atom in the polymer, we determined 1.84% of residual bromine in the material from elemental analyses. This value is quite low and indicates that these chains do not bear systematically one bromine atom per chain end. So, this would have probably little influence on the different properties studied.

In this method, what is the effect of adding sulfuric acid?

And when I do this experiment, there is no precipitated in the process of pouring the mixture into the sulfuric acid and the product floats on the sulfuric acid. And the product sticks to the beaker. What's wrong?