Carbamate (U)rethane Links 

The links in polyurethanes, specifically the urethane (carbamate) linkages, are covalent bonds. In the polymer structure, each bond forms when an isocyanate group (R–N=C=O) reacts with an alcohol (R'–OH), creating a carbamate group (R–NH–C(O)–O–R').

To break it down:

1. Covalent Bonding in Urethane Links: The isocyanate’s carbonyl (C=O) reacts with the alcohol’s hydroxyl (–OH) group. The result is the covalent urethane linkage (or carbamate group).

2. Intramolecular Bonding: Within each urethane linkage, strong covalent bonds hold atoms together in the specific carbamate structure.

3. Polymer Chain Linkage: These covalent urethane bonds are repeated throughout the polymer chain, creating the long, stable molecular structure typical of polyurethanes.

In essence, urethane links are covalent bonds formed through a nucleophilic addition reaction between an isocyanate and an alcohol, leading to the polymerized structure that characterizes polyurethanes.