Because the reduction of catalyst loading is an important factor
in terms of practicality, we also evaluated the effect of the
amount of the Pd catalyst on the polycondensation. With conventional
heating, decreasing the catalyst loading from 5 to
1 mol % resulted in a polymer with a decreased molecular
weight (Entry 2). Alternatively, under microwave heating, the
reaction conducted for 20 min facilitated a reduction in the
catalyst loading to 1 mol %, which gave a polymer with a
comparable molecular weight to that obtained with conventional
heating for 24 h with 5 mol % of Pd (Entries 1 and 8).
Consequently, microwave heating resulted in a decrease in the
required catalyst loading for the polycondensation reaction