Summary: Comparative studies of photoinitiation processes using camphorquinone (CQ) and benzophenone (BP) as light absorbers were performed. The experimental results show that after the transformation of (phenylthio)acetic acid (PTAA) into its tetrabutylammonium salt (PTAA AS), a substantial decrease of the polymerization photoinitiation ability for the CQ–PTAA AS pair in comparison to the CQ–PTAA pair is observed. The mechanism of the photoinitiated polymerization for the tested photoredox pair was clarified based on laser flash photolysis experiments obtained using benzophenone as an electron acceptor and (phenylthio)acetic acid and its tetrabutylammonium salt as electron donors in solution in MeCN. It is documented and deduced that the photoreduction of benzophenone in the presence of (phenylthio)acetic acid and its tetrabutylammonium salt occurs by a photoinduced electron transfer process, while for CQ as initiator, the free radicals are formed by hydrogen atom abstraction by the triplet state of camphorquinone.Schematic of the transients formed after an electron‐transfer process for benzophenone–PTAA and benzophenone–PTAA AS pairs.magnified imageSchematic of the transients formed after an electron‐transfer process for benzophenone–PTAA and benzophenone–PTAA AS pairs.

Several dyes containing benzylideneimidazopyridine moiety (BIPDs) were synthesized and evaluated as photoinitiators for free‐radical polymerization induced with the visible emission of an argon‐ion laser. One method of dye structure change was applied in our study. The modification was based on the character of the substituent introduced into both the imidazopyridine skeleton and phenyl ring. Several different groups were tested including heavy atoms (CI, Br) as well as electron‐accepting (NO2), and electron‐donating groups [N(CH3)2, OCH3]. Analysis of the dye properties demonstrated that there is a significant heavy atom effect on the photoinitiation ability of the novel dyes in both cases, for example, when a heavy atom is introduced into the phenyl ring as well as into the imidazopyridine part of the molecule. The introduction of an electron‐acceptor or electron‐donor group into the phenyl part of the dye caused a dramatic decrease in its photosensitivity. The type of applied counterion had no effect on the overall sensitivity of a dye. BIPDs are not particularly good photoinitiators. Further modification of the dye structure involved the elimination of the motion of a CC bond by the coplanarization of the styrylium residue with other parts of the dye. This approach decreased the degree of branching of the dye, which stabilized the molecule in its excited state. The formed dye, quinoline[2,3‐b]‐2,3‐dihydro‐1H‐imidazo[1,2‐a]pyridinium bromide (QDIPB), exhibited dramatically enhanced sensitivity. QDIPB possessed broad structured spectra with a long‐wavelength part shifted to the blue as compared to other BIPD dyes. The change of the absorption spectra and its high photoinitiation ability makes QDIPB a good candidate for the photoinitiating system applied in dental restorative materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3048–3055, 2003

New materials, such as polymer inclusion membranes, can be used for water and wastewater treatment. In this paper, the selective transport of silver(I) and zinc(II) ions from nitrate solutions through the polymer inclusion membranes (PIMs), which consist of cellulose triacetate as a polymeric support, o-nitrophenyl pentyl ether as a plasticizer, and either 1-hexylimidazole (1) or 1-hexyl-2-methylimidazole (2) as an ion carrier, is studied. Both Zn(II) and Ag(I) model solutions (CM = 0.001 M, pH = 6.5), as well as the solutions after the leaching of a spent battery with a silver–zinc cell (silver-oxide battery), are tested. The results show that Zn(II) ions are effectively transported through PIMs containing either carrier, whereas Ag(I) is more easily transported through PIMs doped with (1). In the case of the leaching solution after 24 h transport, the recovery coefficients of Ag(I) and Zn(II) for PIMs doped with (1) are 86% and 90%, respectively, and for PIMs doped with (2), 47% and 94%, respectively. The influence of basicity and structure of carrier molecules on transport kinetics is discussed as well. PIMs are characterized by using an atomic force microscopy (AFM) technique.

Polymer inclusion membranes (PIMs) doped with ethylenodiamino-bis-acetylacetone as fixed carrier was applied for the investigation of the facilitated transport of Zn(II), Cr(III), and Ni(II) ions from an aqueous nitrate feed phase (cM = 0.001 mol/dm3). The optimal membrane composition (amount of carrier and o-NPPE-plasticizer) was determined. For the optimal polymer inclusion membranes doped with ethylenodiamino-bis-acetylacetone, the following patterns of transport selectivity were found: Zn(II) > Cr(III) > Ni(II). The initial flux of Zn(II), Cr(III), and Ni(II) ions was 6.37 µmol/m2∙s, 5.53 µmol/m2∙s, and 0.40 µmol/m2∙s, respectively. The selectivity coefficients equal to 1.2 and 15.9 were found for Zn(II)/Cr(III) and Zn(II)/Ni(II), respectively. After 24-h transport, the recovery factor of Zn(II), Cr(III), and Ni(II) were 90%, 65%, and 6%, respectively. The polymer inclusion membranes doped with ethylenodiamino-bis-acetylacetone were characterized by scanning electron microscopy and non-contact atomic force microscopy. The influence of membrane morphology on transport process was discussed.