Revisit to the photocrosslinking behavior of PVA‐SbQ as a water‐soluble photopolymer with anomalously low contents of quaterized stilbazol side chains

The photocrosslinking behavior of poly(vinyl alcohol) (PVA) substituted with 0.1, 0.3, 1.3, and 4.0 mol % of styrylpyridinium (SbQ) (PVA‐SbQs) side chains was reinvestigated. Even‐order derivative spectra of films of PVAs loaded with 0.1 and 0.3 mol % of SbQ revealed the presence of subpeaks owing to vibrational transitions, whereas PVA bearing 1.3 and 4.0 mol % of SbQ displayed a new blue‐shifted band (H‐band) at 328 nm due to H‐aggregation. Changes in derivative spectra disclosed the rapid disappearance of the H‐band of PVA‐SbQs under UV irradiation within exposure doses of 10 mJ cm^?2. On the other hand, the films of the PVA‐SbQs were insolubilized upon UV irradiation at exposure doses of 2 and 3 mJ cm^?2, respectively, leading to the conclusion that the high photosensitivity comes from the photodimerization of H‐aggregate as a ground‐state dimer. Fluorescence measurements implied the presence of J‐aggregate at 386 nm, but the involvement of the J‐aggregation in photocrosslinking was excluded because of its negligible fraction. A photosensitive emulsion of poly(vinyl acetate) emulsified with PVA‐SbQ exhibited similar changes in higher‐order derivative spectra in film and applied to fabricate a stencil for screen printing with aid of an LED‐emitting 375 nm light. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012