Dear Mahrokh Moradi

Your bifunctional monomer has two reactive groups—an acid chloride and a chloroformate. Between the two, the acid chloride is much more reactive. So, when you add decanediol first, it reacts preferentially with the acid chloride to form ester linkages, starting the formation of oligomers. After some time, when you add pyridine, it acts as a base to neutralize the HCl formed during the acid chloride reaction. At the same time, pyridine promotes the reaction of the remaining chloroformate groups with the diol, allowing the polymer chain to grow further and giving you the final polymer.

The problem comes when you try to mix everything at once: monomer, diol, and pyridine. In this case, pyridine reacts immediately with the acid chloride groups, forming pyridinium salts. This reaction happens faster than the reaction between the acid chloride and the diol, which means the diol doesn’t get a chance to react before the acid chloride's ends are already “blocked.” Once pyridine has reacted with the acid chloride, those sites become much less reactive, and the diol can't displace the pyridine easily. Meanwhile, the chloroformate group is less reactive to begin with, and now there’s no strong driving force for it to react either. As a result, polymerization fails.

So the key point is that pyridine, if present too early, competes with the diol and shuts down the key initial steps needed for polymer formation. That’s why your two-step method works better—it lets the diol react first with the more reactive acid chloride, and only afterward does pyridine come in to clean up the HCl and support the slower second reaction with the chloroformate.

Thanks

Thank you very much for your complete explanation. I think the same way, but unfortunately, my PI is not convinced by this explanation. She believes that we can get the polymer once we add all at the same time and there is a solution. I wonder if you have any ideas to apply for this problem and solve the problem. I am thinking of using the picryl chloride to make the carbon double bond O of acid chloride and chloroformate more electrophilic then the OH from dialcohal can attack and we would probably get the polymer. Do you think this idea could work?

Dear Mahrokh Moradi

Thanks for clarifying.

I understand the goal is to make the polymerisation work by adding all components at once. Mechanistically, the challenge seems to be that pyridine, being nucleophilic, can react with the acid chloride too quickly, forming acyl pyridinium intermediates that are less accessible to the diol. While I had considered using picryl chloride to make the carbonyls more electrophilic, it’s unlikely to help in this case; it doesn’t activate acid chlorides or chloroformates directly and could lead to side reactions through nucleophilic aromatic substitution.

A more practical alternative might be to use a base like triethylamine or 2,6-lutidine. These are strong enough to neutralise the HCl but not nucleophilic enough to compete with the diol, allowing the polymerisation to proceed more cleanly. This could give us the one-pot approach we’re aiming for without interfering with the initial key steps of chain formation.

Hopefully, this idea will work.

Unfortunately, we tried the triethylamine before, and it did not work. I will try one more time just in case. For picryl chloride, I found an article that they used the dicarboxylic acid with diol in pyridine and picryl chloride to make the polyester. That's why I wanted to share with you to see why you think. But thank you so much for helping me. I will be keeping in touch.

That’s a really smart observation, and the fact that you found a paper using picryl chloride successfully in ester formation is a great sign. Even though it’s not the standard route for acid chlorides or chloroformates, thinking outside the box is exactly how breakthroughs happen. Sometimes, the unusual approach is the one that works best for a specific system. Keep experimenting, trust your instincts, and don’t be afraid to challenge what’s “supposed” to work. You’re on the right track, and I’m excited to see where your creativity leads. You’ve got this!

Thank you so much for your encouragement. I really appreciate it. We do not have the chemical. Let's see if I can convince my PI to buy it and try it. I am so excited for this experiment. Again, thank you so much for your fast replies and your encouragement.

@ Hi Md.Rehan Alam. Can you please help me with one question relating to this type of stuff? My small molecule has both functional groups ( acid chloride and chloroformate). I need to do vacuum distillation to get it pure. But I noticed the HCl is coming; it broke my vacuum pump. I am purging before I do the vacuum distillation, but it has been 4 days, and still the HCl is coming out. Do you know the reason for this observation? I really appreciate if you can help.

@ Md.Rehan But I have a challange with the senario that we discussed for the reaction of bifunctional group, diol and pyridine. When pyridine reacts with acid chloride it makes it more electrophile that the diol as a nuclephile can attack. Right? I did the reaction with decanol ( the alcohal) as a model to see if the both side reacts and it reacts. Still I am confused why I cannot get the polymer.@ Md.Rehan

@ Md.Rehan But I have a challange with the senario that we discussed for the reaction of bifunctional group, diol and pyridine. When pyridine reacts with acid chloride it makes it more electrophile that the diol as a nuclephile can attack. Right? I did the reaction with decanol ( the alcohal) as a model to see if the both side reacts and it reacts. Still I am confused why I cannot get the polymer.