Characterization and gas‐permeation properties of crosslinked diacetylene‐containing polymer membranes from ferulic acid

Thermally and UV crosslinked poly[propargyl(3‐methoxy‐4‐propargyloxy) cinnamate] (PPOF) were investigated in terms of their physical, thermal, optical, and gas‐permeation properties. The crosslinked membranes had high gel contents because of the formation of a diacetylene network. The wide‐angle X‐ray diffraction patterns showed that all of the membranes were amorphous in structure, regardless of the type of crosslinking reaction. The membrane density increased after the crosslinking reaction; this suggested that the free volume of the crosslinked membrane was lower than that of the untreated membranes. Drastic color changes in the membranes were also observed because of the highly conjugated crosslinked network of diacetylene. In addition, the conjugation caused by diacetylene crosslinking led to visible absorption within the range 400–600 nm. The gas permeation of the crosslinked membrane was reduced compared with that of the untreated membranes. In particular, the gas permeability of the thermally crosslinked membrane was lower than that of UV‐irradiated membrane. On the basis of this result, the degree of crosslinking by thermal treatment was higher than that of UV irradiation. Hence, the crosslinked PPOF membranes showed improved gas‐barrier properties due to the high conjugation of the crosslinked diacetylene network induced by thermal treatment and UV irradiation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013