[madscientist]

Hi all,

Ive read in a few different text books that a polyurethane is produced from the reaction between a diol and a diisocyanate.  Ive also read that a polyurethane is any polymer consisting of a chain of organic units joined by urethane links.  Would a polyurethane be produced from the reaction between a dicarboxylic acid and a diisocyanate? I cant seem to think of any reason why it wouldn't, any suggestions?

[movies]

A urethane is the O-C(=O)-N functional group (also called a carbamate).  Since you have added another carbonyl to that, it's not going to behave like a normal urethane.  The properties would probably be a lot different, and I would guess that would be in a bad way because you have increased the possibility of hydrolysis of the carbamate or ester.

In terms of reactivity, however, I am pretty sure that the reaction would occur as you have drawn, but isolation might be difficult in the presence of water.

[DrCMS]

Acids slow down the reaction of isocyanates with diols.  In a reaction I know the addition of just 20g of Phosphoric acid to 10T of diol more than doubles the reaction time.

So i'm not sure that reaction an acid with an isocyanate will give the product you describe.