Luminescent Emission And Mechanism Of Functional Polyurea Materials

Organic luminogens have attracted increasing attention owing to their unique photophysical properties and wide applications in organic light-emitting diodes,organic lasers,optical waveguide,drug delivery,chemo-/bio-probes,bioimaging,and so on.Most conventional chromogens,however,suffer from the disreputable aggregation-caused quenching?ACQ?.They are dramatically emissive in their dilute solutions while become infirmly luminous or even non-luminescent in condensed solutions or solids,which has been an infamous problem and immensely restricted their actual applications in aggregated or solid states.Thanks to the discovery of the aggregation-induced emission?AIE?phenomenon in2001,a new way to design and construct novel fluorescent materials has opened,and the unique light-emitting behavior has been becoming cumulatively more and more attractive owing to their bright application prospects in biological technology and materials science.In the AIE area,the research has been focused on low mass molecules,and much less attention has been paid to polymers,although they possess their unique properties such as good film-forming ability,amplification effect of the signals,and multiple functionalization,which facilitates their practical applications.In this work,aromatic polyura?TPU4?and aliphatic polyamide were synthesized and their fluorescence mechanisms were studied.In the second part of the thesis,an aromatic polyurea?TPU4?was synthesized from copolymerization of toluene diisocyanate?TDI?and butanediamine,and their fluorescence properties in solid state and in solution of different concentration were studied.TPU4 with different molecular weights was synthesized and the effect of molecular weight on the fluorescence properties was discussed.N-TPU4 was synthesized by copolymerization of N,N'-Dimethylethylenediamine and TDI.HPU4 was synthesized by copolymerization of hexamethylene diisocyanate and butanediamine.Based on the structures of TPU4,N-PU4 and HPU4,their structure-property relationship was discussed.TEM photos were taken and the particle size distribution were detected for TPU4 at different concentration.The results demonstrate that the strong fluorescence,both in the solution and solid state,was observed.It also has concentration enhanced emission effect and molecular enhanced emission effect.The nanoclusters were formed in TPU4 solution,and their size was increasing with the concentration.TPU4 also has excitation-dependent photoluminescence property.In the third part of the thesis,polyamide?PA24?,a linear aliphatic polymer was synthesized by copolymerization of succinic acid and ethylenediamine.Its fluorescence property in solid state and in solution at different concentration was studied.The effects of concentration,temperature,viscosity and pH on the fluorescence properties were discussed.The results demonstrate that strong fluorescence,in both the solution and solid states,was observed.It also has concentration enhanced emission effect and aggregetion enhanced emission effect.Particle size distribution detection and the TEM photos demonstrated that nanoclusters were formed in PA24 solution,and their size was increased with the concentration.The fluorescence emission of PA24 originated from the nanoclusters formed by hydrogen bonds between amide groups.Moreover,photoluminescence?PL?wavelength of PA24 can be tuned simply by varying the excitation wavelength,without changing their chemical composition or size.In the fourth part of the thesise,the cell viability and photostability of PA24 were examined at first.Because of the excellent photostability and low cytotoxicity,PA24 is suitable for fluorescence cell imaging.In addition,PA24 aqueous solution showed a strong selective quenching with respect to Cu²⁺and a good liner relationship between the fluorescence intensity and Cu²⁺concentration was found in the concentration range of0.0003M to 0.003 M with a correlation coefficient?R?of 0.9945.