Studies On Design, Synthesis, Photophysical Properties Of Linear And Hyperbranced Poly(Phenyleneethynylene)

Water-soluble conjugated polymers (WSCPs) possess π-conjugated backbones and hydrophilic pendent chains. Because WSCPs combine the excellent optoelectronic properties of conventional conjugated polymers with the solubility and the electrical properties of the polyelectrolytes. they have caused growing interest in the field of organic functional polymer materials.On the other hand,, polymers with hyperbranched structure have now become a hot research topic. Hyperbranched conjugated polymers can effectively improve the self-quenching of fluorescene caused by self-aggregation of linear macromolecules. Moreover, hyperbranched polymers can be modified by changing the nature of their nuclear unit or side chain groups or some other methods to adapt their applications in different fields. The acetylenic bonds of poly(phenylene ethynylene)(PPE) have unique cylindrical electron cloud configuration, there will be less influence to the delocalization of electron cloud in the presence of the angle between adjacent benzenes, it favorite the migration of singlet excitons in polymer’s backbones. Therefore, in this thesis, we introduced hyperbranched structure into water-soluble PPE. and studied the structure-property relationships in contrast with linear water-soluble PPE. The contents are as follows:1. New water-soluble hyperbranched poly(phenylene ethynylene)(HBP1) was synthesized by the simple A2+A2’+B3protocol based on Sonogashira reaction, and we use the monomers bearing long alcoxyl chains. The linear poly(phenylene ethynylene) analogue(LPl) was also synthesized for comparison. The different photophysical property caused by structure was discussed.2. To deeply demonstrate the structure-property relationship of the polymers, another water-soluble hyperbranched poly(phenylene ethynylene)(HBP2) and linear poly(phenylene ethynylene) analogue(LP2) bearing more density of side chains were synthesized. Compared to HBP1and LP1, the solubility of HBP2and LP2is improved. By means of analyzing the UV-Vis and PL spectra, redshift was observed from HBP2and LP2to HBP1and LP1respectively.3. The interactions between double-stranded DNA (dsDNA) and WSCPs were studied using ethidium bromide (EB) as fluorescent probe. The HBP2’ can form more stable complex with dsDNA compared to LP2’,it is attributed to introducing the branch unit which can prevent the formation of π-stacking aggregates between conjugated polymer backbones. Meanwhile, the HBP2’possessed higher charge density than HBP1’ can form more stable complex with dsDNA through electrostatic interactions.