The design, synthesis and characterization of polyurethane with super macromolecular size

In the synthesis of polyurethane (PU), utilizing the property that –NCO at chain end in prepolymer can react with the hydrogen in –NHCOO– [Solomon DH, editor. Step-growth polymerizations. New York: Marcel Dekker, 1972 [Chapter 3].], a reaction system with cross-linking tendency is designed. Due to the cross-linking tendency, molecular weight will increase unlimitedly, meanwhile, intramolecular reaction presenting in the system consumes –NCO groups and then the cross-linking reaction can be prevented finally. By this way, PU with extremely complex structures and super macromolecular size is synthesized. When the molecular weight of the soft segment is 900, and the amount of chain extender is reduced by 40%, the molecular size is 750 nm. Compared with the polystyrene, which has a molecular weight of 2×106, the molecular size is only 96 nm, it is undoubtedly a super macromolecule. Elongation and extensile strength at break of this PU sample are 1683% and 28,000 N/cm2, respectively. When the molecular weight of the soft segment is 1684, elongation and extensile strength at break are 2300% and 51,000 N/cm2, respectively.