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N,N′-Bis(1-pyrenylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (1) and N-(1-pyrenylmethyl)-1,4,7,10,13-pentaoxa-16-azacyclooctadecane (2) were synthesized and found to display unique photophysical properties in the presence of the guest-metal salts. The binding of metal ions to the diazacrown ether 1 cavity inhibited the exciplex formation and changed the distance between two pyrenyl groups. This caused not only an emission-intensity enhancement, but also a large change in the monomer/excimer fluorescence-intensity ratio. The change resulted from the coordinated structure and exchange process between the free host 1 and its metal salt complex in the ground state.

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Various epoxy monomers containing norbornadiene (NBD) moieties were prepared by reactions of potassium salts of NBD derivatives with excess epichlorohydrin using tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. The copolymerization of glycidyl (3-phenyl-2,5-norbornadien-2-yl)carboxylate (GPNC) with phthalic anhydride (PAn) proceeded smoothly using TBAB as a catalyst in sulfolane at 100 °C for 24 h to give polyester P-1 containing pendant NBD moieties. Copolymerizations of various epoxy monomers containing certain NBD moieties with carboxylic anhydrides gave the corresponding NBD polyesters in good yields. The photochemical valence isomerizations of the NBD moieties in the polymers were carried out in the film state or in the solution. Rates of the isomerizations of some NBD moieties in the polymers were strongly enhanced by the addition of photosensitizers such as 4-(N,N-dimethylamino)benzophenone (DABP). The T gs of the polyesters having NBD residues and stored thermal energy in the corresponding quadricyclane (QC) groups in the polymers were measured by DSC analysis. The T gs of the NBD polymers were 45−93 °C. Polyesters having QC groups after photoirradiation released their stored thermal energies (about 90 kJ/mol) at temperatures above the T gs of the corresponding NBD polymers.

An investigation was undertaken to gain understanding of the type of bond cleavage (heterolysis versus homolysis) of 1-(methoxy-substituted arylmethyloxy)-9,10-anthraquinones (1) as bichromophoric photoinitiators of styrene (St) and cyclohexene oxide (CHO) polymerization to aid development of a novel and efficient hybrid photoinitiator. Results indicated that the 4-methoxynaphthalen-1-ylmethyl-substituted photoinitiator 1 containing no halogen or metal induces radical and cationic polymerization reactions of St and CHO, respectively, to give the corresponding polymers in reasonable yields. This initiator also accomplished hybrid photopolymerization of an equimolar mixture of St and CHO, although the ability to initiate polymerization was reduced. Analysis of the photoproducts derived from specific initiators as well as of the polymer end groups substantiated that the arylmethyloxyl radical and arylmethyl carbocation are major reactive species initiating the polymerization of St and CHO, respectively. In addition, the charge-separated state characteristic of the 9,10-anthraquinon-1-yloxy chromophore in the singlet excited state played a pivotal role in the heterolytic bond-cleavage in the latter monomer. 1 Recent research has focused on novel photoinitiators that promote the initiation of both radical and cationic polymerizations, 2-8 because a combination of these two types of polymerizations could produce a hybrid polymer composed of radical-and cation-derived polymer units. For example, interpenetrating network polymers 9-11 that combine the properties of these two polymer units present an attractive research subject due to potential practical applications.While some salt-type photoinitiators can initiate both cationic and radical polymerizations, [2][3][4][5]8,12,13 they have limited industrial application because of problems such as low solubility in monomers and the need for metal-or halogen-containing inorganic initiators. To overcome these problems, nonsalt-type photoinitiators have been developed, but they induce only minor hybrid polymerization. 6,7,14 A systematic study on the photoreactivity of O-substituted anthracene-9-methanol derivatives in methanol revealed that an intramolecular charge transfer interaction in their singlet excited states assists heterolytic CH 2 -O bond cleavage to generate ion pairs along with radical pairs.15 Therefore, these derivatives are good candidates for a novel hybrid-type photoinitiator containing no halogen or metal. While O-acyl anthracene-9-methanol functioned as a photoinitiator for the radical polymerization of styrene (St), the cationic photopolymerization of cyclohexene oxide (CHO) was induced only to a minor extent.14 This finding suggests that the much lower polarity of CHO compared with that of methanol results in inefficient heterolytic bond cleavage in the singlet excited state. Therefore, an investigation was undertaken to develop a hybrid-type photoinitiator that would undergo much more efficient heterolysis in CHO. To accomplish this, 2-arylmethyloxy-6-...