Do you mean the carbonly group in your polymer shiffted to lower wave numbers.or what?
Dear Alaa
Yes, of course.
The carbonyl group in prepared polyurethanes shifted from upper than 1715 cm-1 to below than 1700 cm-1.
Based on my knowledge, it must be assigned to the hydrogen bonding. However, I heve not found any 3D conformation for this object.
As you says a decrease in the frequency has to be correlated with stronger hydrogen bonds, that will asociate a change in the conformation. Depending if it is
a polyester or polyether urethane you should see different frequency shifts on the NH streching vibration (3200-3300 cm-1). You should review the good works of Coleman and Painter about FTIR spectra on polyurethanes.
Dear Dr. Antxon Martinez de Ilarduya
I would like to appreciate you for your directions. We have observed only one band at 1700 cm-1 therefore, we can not calculate the Hydrogen bonding index.
In our own experience, H-bonding is the most likely cause for this shift. However, regular urethane H-bonding through side-chain interaction will go down to about 1710~1705. Therefore, we believe that your observation must be due to the formation 12-ring size- cyclic conformation with three-carbamate groups and each contribute[-CO- N-H] to the ring where terminal H and O are tightly linked by H-bonding. There are no report in literature about this assignment but this based entirely on our own study on carbamate/urea molecules. (If you need to have the drawn up structure, let me know.)
Shenghong Dai (NCHU, Taichung, Taiwan)
Dear Prof. Shenghong Dai
I would like to express great thanks for your directions. It is my favorite to know the chemical structure of this amazing conformation. As I mentioned, I can't calculate the Hydrogen bonding index because I observed only one band at 1698 cm-1. Moreover, do you have proved this structure by chemical analysis? It is actually interesting if your opinion has a correlation with our observation.
King Regards
Hamed Daemi
Dear Prof. Shenghong Dai
I would like to express great thanks for your directions. It is my favorite to know the chemical structure of this amazing conformation. As I mentioned, I can't calculate the Hydrogen bonding index because I observed only one band at 1698 cm-1. Moreover, do you have proved this structure by chemical analysis? It is actually interesting if your opinion has a correlation with our observation.
King Regards
Hamed Daemi
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