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18.7.1.1.3 Method 3: From Alcohols and Carbamic Esters

DOI: 10.1055/sos-SD-018-00805

Moratti, S. C.; Charalambides, Y. C.Science of Synthesis, (200518657.

The use of carbamic esters to form polyurethanes is a very common industrial process. Carbamic esters 29 are often referred to as blocked isocyanates. Typically, the blocked isocyanate is mixed with the polyol and heated to generate the polyurethane directly. This method is normally only useful in forming thin films, as an alcohol or phenol is generated as a byproduct and must be removed. It is less commonly employed in the laboratory, as there are usually much more reactive monomers available; however, in some cases, the alternative monomers are too reactive to synthesize, and the carbamic ester route becomes attractive. An example involves the use of a blocked isocyanate monomer 30 for the formation of a hyperbranched polyurethane 31 by step-growth polymerization (Scheme 12).[‌31‌]

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