The Synthesis, Assembly Of Novel Conjugated Polymers And Their Application In Fluorescent Chemical Sensor

Conjugated Polymers (CPs) are polymers with conjugatedπelectrons on the po.ymer backbone. The delocalization of the electrons facilitates the electronic and energy migration along the whole polymer backbone, which make it possible for change the overall fluorescence properties of the polymer by a very tiny disturbance from anywhere on the chain. Therefore, compared to small molecules, fluorescent CPs can achieve enhanced sensitivity by"million-fold"amplifying of signals, Even higher sensitivity could be achieved in CP aggregates where multi-dimensional energy or electronic migration exists..CPs received continuing research interest for over 20 years. This thesis is mainly about the design and synthesis of novel CPs and the study of their properties. The second and third chapters discuss about the synthesis of some novel conjugated polymer and their property studies. The second chapter deals about the synthesis of a conjuagted polymer, PPESO3OR, which has hydrophilic and hydrophobic side groups, and its photophysics and application as sensor. In the third chapter, the synthesis of a novel CP, PPEETP, containing pyridazine and thiophene rings in the main chain was discussed. In addition the"one-pot"synthesis of a tri-block co-polymer, PEG-PPEETP-PEG, which contains PPEETP, a hydrophobic chain, in the middle and two hydrophilic PEG chains at two sides was also discussed.. The comparison of photophysics between these two polymers were carried out. In the forth part, we report the synthesis of a CP with azobenzene group in the main chain (PPEPAPE), its photophysics characters and surface morphology in solid thin film state. The fifth chapter, as an extension study of the second chapter, concerns about the synthesis of random PPESOR3OR (RPPESO3OR) and study of its photophysics properties. The results are listed as following:(1) The conjugated polymer PPESO3OR was successfully synthesis by the Sonogashira coupling of a hydrophilic monomer and a hydrophobic monomer. This polymer exhibited amphiphilic properties in common solvents and inherits many characters of polyelectrolytes. Moreover, it can well dissolve in water after drying up, thus overcome some disadvantages of conventional CPs. In addition, the photophysics can be well-controlled through adjusting the solvent. The transformation from an aggregated state to a nonaggregated state for the polymer in solution was facilely controlled by titration of THF into dilute aqueous solution, or H2O into a THF/H2O solution with 99.9% of THF, High sensitivity toward analytes, such as, Fe3+ was realized in some polymer systems. The highest fluorescence quenching effect with an I/I0 value of 148 was achieved in the solution having a THF/H2O ratio of 30/70, which could be attributed to a delicate balance among all influencing factors for the fluorescence quenching systems, the initial fluorescence, the rate of energy migration, and the accessibility of the receptors.(2) The conjugated polymer PPEETP was synthesized via Sonogashira coupling of two pre-synthesized momonors. . The PEG-PPEETP-PEG was synthesized by"one-pot synthesis". This copolymer was composed by one hydrophobic rigid fluorescent conjugated block in the middle and two amphiliphic flexible PEG block at two sides . This"one-pot synthesis"was simple compared to previous reported synthesis of similar structures The comparison of photophysics between these two polymers was carried out and some of the difference could be attributed to the self-assembly of the block copolymer in the solution.(3) We report the design and synthesisof the precursor and then the conjugated polymer having azobenzene building block in the backbone. The experimental results shows that it didn't have fluorescence emission while had a broad absorbance in solid state thin film. In addition, we surface morphology of the film was studies by the suface electronic microscopy (SEM) and the relationship between the photophysics and morphology was discussed.(4) To further investigate the assembly of conjugated polymers with symmetrically assembled hydrophobic and hydrophilic side groups in different solvents, RPPESO3OR was synthesized by reducing the density of side groups. It turned out to be much easier for synthesis and work-up, while photophysics are very similar to that of PPESO3OR. However, this RPPESO3OR has reduced solubility in the common solvent due to the reducing of the side chains. More studies about the photophysics and other properties are still on-going.