| In recent years, the study of environmental stimulus-response polymers provides a favorable platform for the development of polymer intelligent materials. Environmental stimulus responsive polymer is a kind of intelligent polymer materials which can produce a corresponding physical or chemical structure, mechanical properties changes to respond to the subtle changesof external environment (temperature, pH, solvent, irradiation, ionic strength, electromagnetic field, mechanical force, and ultrasonic). It plays an important role in terms offunctional regulation vailablenew materials, biological or chemical sensing, drug and gene transfer, biological separation, tissue engineering and intelligent optical system. Among them, the environmental stimulus-response fluorescent polymers have the advantages of high sensitivity and good selectivity,they have potential applications in the fields of life science, chemistry, medicine, military and so on. P(NIPAM-co-RhBHA)-NP and P(NIPAM-NBDAE-RhBAM) were prepared by free radical copolymerization and their environmental stimulus-response fluorescentbehavior were also studied. The specific contents of the paper are as follows:1. In the present study,based on spectral overlap between 1,8-naphthalimide and N-acrylyl-N’-rhodamineBacylhydrazinethiourea (RhBHA), reversible"on-off" ring reactionat various pH values, opening-ring reaction with Hg2+of RhBHA, and thermosensitive property of poly(N-isopropyl acrylamide) (PNIPAM), a novel linear polymer P(NIPAM-co-RhBHA)-NP was prepared via a series of chemical reactions. Firstly,4-(2-aminoethyl)amino-N-aminopropane-1,8-naphthalimide(NP-NH2) and RhBHA were prepared respectively, and they were used as the donor and acceptor to construct a fluorescence resonance energy transfer(FRET) system. Secondly, incorporating RhBHA into PNIPAM by reversible addition-fragmentation chain transfer polymerization (RAFT), P(NIPAM-co-RhBHA) was synthesized. Finally, P(NIPAM-co-RhBHA)-NP was fabricated by amide condensation between NP-NH2 and the as-prepared P(NIPAM-co-RhBHA). The structure of P(NIPAM-co-RhBHA)-NP was characterized via 1HNMR, FTIR, UV-vis, elemental analysis and GPC. The fluorescence responsive behavior of the polymer to environmental temperature, pH value and Hg2+ was investigated by photoluminescence(PL) in buffer solution, and the mechanism was discussed in detail. The results indicate that, in an acidic solution, energy can be transferred from NP-NH2 moieties to RhBHA moieties via FRET mechanism, either the changes of pH values or environmental temperatures and mercury ion density play important roles to affect the fluorescence emission of P(NIPAM-co-RhBHA)-NP.2. The fluorescence emission spectra and the fluorescence execiting spectra of 4-(2-aciyloyloxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBDAE) and RhBAM respectively overlep well and RhBAM can changes from non-fluorescent to fluorescent which has efficient fluorescence emission. So, in the present study NBDAE and RhBAM were used as the donor and acceptor respectively, combining the thermosensitive property of PNIPAM, we prepared a kind of nanogel P(NBDAE-NIPAM-RhBAM) which can achieves FRET"on-off’via changing the pH values and has the property of thermosensitivity by free radical copolymerization.The as-prepared P(NBDAE-NIPAM-RhBAM) nanogel was characterized via FTIR and TEM. The fluorescence responsive behavior of the polymer to environmental temperature and pH valuewas investigated by photoluminescence (PL) in aqueous solution, and the mechanism was discussed in detail. The results indicate that, in an acidic solution, energy can be transferred from NBDAE moieties to RhBAM moieties via FRET mechanism, either the changes of pH values or environmental temperatures play important roles to affect the fluorescence emission of P(NBDAE-NIPAM-RhBAM) and the thermal influence mechanism to fluorescence emission of hydrogel was different from linear polymers. |
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