Synthesis and structure properties of polyurethane based conducting copolymer I. 13C NMR analysis

A series of urethane–aniline block copolymers based on polyurethane prepolymer and oligomer of amine-terminated polyaniline (OPA) were prepared for a conductive material and characterized by 13C NMR and FTIR. The amine-terminated functional groups of OPA were introduced into the polyurethane (PU) structure as a chain extender to form the hard segment of the copolymer with urea-linkage. Solid-state 13C NMR techniques were used to investigate the microphase structure of the copolymers. 1H spin relaxation times both in the laboratory frame (T1(H)) and in the rotating frame (T1ρ(H)) were carried out on these copolymers to detect, on the nanometer scale, the change of the microphase structure. The resultant copolymers demonstrate a higher tensile strength due to inducing the long rigid rod structure of OPA into the copolymers. The conductivity of the copolymers is found to be ranging from 0.83 S/cm for the neat OPA to 6.17×10−5 S/cm for the urethane–aniline block copolymers. Various contact time CP experiments show that TCH and T1ρ(H) of the soft segment carbons decrease with the increase in the content of OPA. These results indicate that the chain mobility and the domain size of the soft segment in the copolymers gradually decreased as the content of OPA was increased.