Solid-State 13C NMR Analyses of the Microphase-Separated Structure of Polyurethane Elastomer

Abstract

Solid-state 13C NMR analyses have been performed to obtain information about the microphase-separated structure for polyurethane (PUR) elastomer, which is prepared from p-phenylene diisocyanate (PPDI), poly(tetramethylene oxide) (PTMO), and 1,4-butanediol (BD). 13C spin−lattice relaxation time (T1C) analyses have revealed that three components with different T1C values exist for the PPDI and BD residues, while two components are observed for the PTMO carbons. The longest T1C components of the PPDI and BD carbons are assigned to the crystalline component, whereas the PTMO carbons with shorter T1C's and the PPDI and BD residues with shortest T1C's are ascribed to the rubbery component. Moreover, the PPDI and BD residues with the medium T1C values and the PTMO carbons with the longer T1C values are found to be assignable to the interfacial component by the T1C measurement for the component selectively created through the 1H spin diffusion from the rubbery component. The mass fraction values of the three components thus assigned are determined for the respective structural units; in the PPDI units, for example, the mass fraction values 0.40 for the crystalline component, 0.16 for the interfacial component, and 0.44 for the rubbery amorphous component. On the basis of these results, the microphase-separated structure is discussed for the PUR elastomer.