No abstract

Polymers having both crown ether moieties as cation binding sites and cinnamic acid ester moieties as photodimerizable pendant groups were prepared. On irradiation with UV light the cinnamic acid ester groups of the polymers caused dimerization in dilute solution without formation of any insoluble material. Irradiation was carried out in THF and THF-methanol (1 : 1 vol. ratio) in the absence and presence of cations as a template, respectively. The cation binding properties were investigated by means of the method of picrate salts extraction. The cation extractability of the photoreacted polymers was higher than that of the original polymers. Furthermore, the cation binding ability of the photoreacted polymers was less sensitive to temperature than that of the original polymers. The effect of the degree of photodimerization of the polymers, of the kind of cations used as a template during photodimerization of the polymers, and of the concentration of the template cation on the extractability of polymers were investigated in detail.

Polymers having both crown ether moieties as cation binding sites and cinnamoyl moieties as photodimerizable pendant groups were prepared by cationic polymerization of 2-vinyloxyethyl 3-(2,3-benzo-1,4,7,10,13-pentaoxacyclopentadecen-4'-yl)acrylate (1) or 2-vinyloxyethyl 3-(2,3benzo-l,4,7,10,13,16-hexaoxacyclooctadecen-4'-yl)acrylate(2). The copolymer 3 a was also prepared from 1 and 2. On irradiation with UV light, the cinnamoyl moieties of the polymers undergo dimerization in solution. The cation binding properties were investigated by using a fluorescent probe, 8-anilino-1-naphthalenesulfonate. The cation binding ability of the photoreacted polymers was found to be higher than that of the original polymers. A significant template effect of alkali metal chlorides during photodimerization reaction on the cation binding ability was observed. The copolymers 4a, prepared by irradiation with template cations, show a remarkable rubidium cation selectivity, which is not observed for polymers with only 15-crown-5 or 18-crown-6 moieties.

SynopsisThe polymers which have different sized crown ethers as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the cationic copolymerization of corresponding monomers. The crown-cation complexation ratio (1 : 1 or 2 : 1) was investigated by measuring quantum yields @ of the photodimerization of the crown-connected cinnamoyl units in the presence of alkali metal chlorides and also by measuring the shift of A,, of alkali metal picrates in THF on addition of the crown polymers. A significant 1 : 2 complex formation of alkali cations with two different sized crown ether units in the side chain of the polymers was confirmed. The alkali metal cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were markedly different from those expected from the combination of polymers of same ring-size crown ether units. When irradiated with ultraviolet (vv) light, the cinnamic acid ester groups of the polymers caused dimerization even in dilute solutions. The cation binding ability of the polymers was largely enhanced by the photodimerization of the cinnamoyl moieties with suitable template cations.In the previous