So I am having trouble with the solubilty of my polycarbonate. We make these using diols and triphosgene in chloroform solution with a large molar excess of pyridine. I wanted to know if using TEA would better solvate the polymer (as opposed to pyrindine) during the reaction so I dissolved some polycarbonate powder in chloroform and added TEA and there was an immediate exothermic reaction. Anyone have any idea why?
Sometimes, the enthalpy of mixing can be quite high. In this case, it seems the enthalpy of mixing is -16 Kj/mol due to formation of some sort of complex; which would account for a temperature increase of around 30-70° (by my reckoning; because of the unknown heat capacity of the mixture). http://www.nrcresearchpress.com/doi/pdf/10.1139/v89-174
An alternative can be traces of acid or phosgene in the chloroform or polymer.
Ahhh, interesting! I thought I may have had residual acid chlorides in the polymer that were reaction with the TEA to release HCL gas. I didnt even think of the chloroform as the culprit cause Ive always considered it completely inert. Thankx for the insight!
I would first check pH of your chloroform solution (you will need to add some water of course).
Yes, definitely. Perhaps you can try making the solution (Et3N and chloroform), check the temperature, then add the polymer and check again.
I just made some very rough estimates, it's quite possible that enthalpy of mixing is not the chief cause :-) the only way to be sure is to chekc!
The polycarbonate possibly has terminal OH groups attached to phenyl group (phenolic) and coming from excess bisphenol A during manufacture. With triethylamine, there will be exothermic complex formation shown by the equation below:
-Ph-OH + N(C2H5)3↔ R-OH…N(C2H5)3↔ RO-…H-N+(C2H5)3
It has been proven to be exothermic by the reference given in the link.
http://link.springer.com/article/10.1007/BF00859070#page-1
Chlorofrom and triethylamine form a distinct 1:1 complex: http://www.nrcresearchpress.com/doi/pdf/10.1139/v57-156
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