Synthesis, characterization and fiber spinning of poly(caffeic acid)

Abstract

A melt-spinnable poly(caffeic acid) (PCA) was prepared by ester exchange reaction of acetylated caffeic acid at 180 °C for 4 h under vacuum. The PCA showed broad processing window between the glass transition temperature at 101 °C and 5-% weight decrease temperature at 313 °C. The PCA showed shear thinning in the molten state at 180 °C, reflecting the development of molecular orientation under shear. The melt-spun PCA fiber showed Young's modulus of 1.3 to 2.0 GPa, tensile strength of ca. 50 MPa, and elongation at break of 4 to 5 %. The relatively low mechanical strength of the melt-spun fiber is attributed to the loose molecular orientation, that was reflected in the two-dimensional wide-angle X-ray scattering pattern showing the broad azimuthal distribution.