Molecular structure and photosensitivity of polyesters with conjugated double bonds

Photocrosslinkable polyesters of m‐ and p‐phenylenebis(α‐cyanoacrylic acids) (I‐a and I‐b), m‐ and p‐phenylenebis(α‐cyanobutadiene carboxylic acids) (I‐d and I‐e), p‐phenylenebis(acrylic acid) (I‐c), and p‐phenylenebis(butadiene carboxylic acid) (I‐f) were prepared, and their photosensitivities were investigated. The spectral sensitivities of I‐a, I‐c, I‐d, and I‐e ranged up to 365, 385, 510, and 560 nm, respectively. This order corresponds to that of λmax due to the π‐π* transition in their absorption spectra. I‐e was sensitive to the visible part of argon ion laser even in the absence of photosensitizer. The highest sensitivity observed with I‐e was estimated to be 1.5 mJ/cm2. In contrast, the sensitivity of I‐c was low (> 105 mJ/cm2) and that of I′‐d, a modified I‐d, was 1300 mJ/cm2, respectively. Addition of 2,6‐di(4′‐methoxyphenyl)‐4‐(4′‐n‐amyloxyphenyl)thiapyrylium perchlorate to them extended their sensitivity range, improving their sensitivity values to 35 and 110 mJ/cm2, respectively.