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. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012