| 초록 |
The stiff helical backbone and self-assembly nature of polyisocyanates have been verified to be great merits for the potential applicability to chiroptical switches, drug vehicles, micropatterning, and photonic crystals. The primary work to take advantage of desirable properties of polyisocyanates is to achieve the controlled molecular weight (MW) and narrow polydispersity. During the living anionic polymerization of isocyanates, it is required to stabilize the living chain-end to completely impede the depolymerizable backbiting reaction that yields the undesirable cyclic trimer. Sodium diphenylamide (Na-DPA) initiator fulfills this prerequisite. In the polymerization condition, Na-DPA molecules exist in the form of 2- or 3-membered cluster, of which one molecule initiates the polymerization of isocyanates and the others protect the living chain-end from backbiting, leading to precise control of molecular properties. The actual initiation efficiency of Na-DPA is constant to ~40%. |
