Copolymerization of N-(prop-1-yne-3-yl)-4-(piperidine-1-yl)-1,8-naphthalimide with Arylacetylenes into Fluorescent Polyacetylene-Type Conjugated Polymers
Abstract
N-(prop-1-yne-3-yl)-4-(piperidine-1-yl)-1,8-naphthalimide (PNPr), i.e., the monomer with a terminal ethynyl group and 1,8-naphthalimide fluorophore, has been successfully copolymerized with a series of monoethynylarenes into well-soluble high-molecular-weight (M-w up to 210 000) linear polyacetylene-type copolymers containing from 14 to 51 mol% units derived from PNPr. The copolymerization of PNPr with bifunctional 4,4'-diethynylbiphenyl provides polyacetylene-type micro/mesoporous fluorescent network containing 8 mol% PNPr units and exhibiting the Brunauer-Emmett-Teller surface of approximate to 1000 m(2) g(-1).
The copolymerizations (catalyzed with acetylacetonato(norborna-2,5-diene)rhodium complex, [Rh(nbd)acac]) proceed smoothly despite the fact that the homopolymerization of PNPr fails. The fluorescence of PNPr (emission at approximate to 510 nm) has been retained after the incorporation of PNPr into the copolymers.
The fluorescence of the copolymers can be induced by a direct excitation of PNPr units or via an energy transfer mechanism. In the latter case, the comonomeric units with aromatic hydrocarbon fluorophores (e.g., of the biphenyl-type) emitting at 380-400 nm (after irradiation with 300 nm UV radiation) serve as energy donors for fluorescent PNPr acceptors.
The difference between the wavelengths of the primary absorbed radiation and the finally emitted radiation is 210 nm.