Phase structure in segmented polyurethanes having fatty acid-based soft segments

Abstract

Abstract: Structural studies on two segmented polyurethanes prepared form the modified oleic acid soft segments and butane diol/diphenylmethane diisocyanate hard segments, were carried out. Polyurethanes were thermoplastic elastomers with soft segment concentration (SSC) of 50% (TPU-50) and 70% (TPU-70). Dynamic mechanical analysis revealed the co-continuous morphology in TPU-50 and dispersed hard domains in the soft matrix in TPU-70. AFM revealed the micron size globules in TPU-70 ascribed to hard segment-rich spherulites and alternating small soft and hard domains in TPU- 50, with lateral dimensions of about 15 nm with local modulus deviations from 40 to 50 MPa, consistent with co-continuous morphology. The dispersed hard domains in the soft matrix for TPU-70, and co-continuous phases in TPU-50 morphology was confirmed. USAXS showed the domain spacing for TPU-50 was about 13.3 nm and about 11.3 nm for TPU-70. USAXS revealed that the interface between phase-separated domains exhibit a surface-fractal-like behavior.