Comparing reactions performed without a catalyst, which is most popular in recent literature, and with a catalyst brings some important information (Table ). Firstly, the catalysed process allows for obtaining polymer with a higher polymerization degree in a much shorter time than without a catalyst. What is essential is that comparing these reactions could indicate that these polymers have very similar structures. Differences are the effect of lower conversion of functional groups in the case of uncatalyzed reactions. Adding a catalyst does not affect the reaction mechanism but only lowers activation energy.