Studies On The Synthesis And Properties Of Topological Polyelectrolytes

Polyelectrolyte has received extensive attention due to its promising applications in various fields. It is well known that the properties of polyelectrolyte are generally determined by its conformation. Owing to their special structure, the topological polymers including block copolymer, grafted polymer, star polymer, hyperbranched and cyclic polymer exhibit unique properties in comparison with the linear analogies. Hence, it is important to investigate the various properties of topological polyelectrolytes. However, synthesis of topological polyelectrolytes still faces a big challenge. In this thesis, by a combination of ATRP and click reaction, we have successfully synthesized the cyclic and star polyelectrolytes and have studied their properties. The results and conclusions are as follows:Based on the direct copper(Ⅰ)-catalyzed click cyclization without any deprotection steps, we have successfully synthesized well-defined cyclic PtBA and PAA. The cyclic PtBA and PAA are confirmed by the GPC, NMR, and FTIR measurements. In another method, the well-defined alkyne terminated PtBA can be directly prepared via ATRP using propargyl2-bromoisobutyrate as initiator by reducing amount of catalyst complex or in proper solvent. The cyclic PAA is obtained by following click cyclization and hydrolysis. The density, viscosity, light scattering, conductivity and DSC measurments demonstrate that the cyclic polyanion exhibit quite different properties compared with the linear analogies. Quartz crystal microbalance studies reveal that the multilayer formed by the cyclic PAA is quite different from that of linear PAA. The strategy provides a convenient and efficient method for synthesis of cyclic polyelectrolyte and can be applied to other systems.By use of atom transfer radical polymerization (ATRP) method, we have prepared well-defined6-arm star-shaped poly[2-(dimethylamino)ethyl methacrylate](PDEM) and poly(acrylic acid)(PAA) containing a fluorescent triphenylene core. We have studied the pH and ion-species sensitive fluorescence properties of such two star polyelectrolytes. For both PDEM and PAA, the fluorescence intensity decreases with increasing pH, indicating that the fluorescence intensity of PDEM and PAA is dominated by the aggregation induced fluorescence quenching and the chain conformation controlled nonradiative relaxation, respectively. This suggestion is further confirmed by the facts that the star PDEM molecules can form excimers at high pHs and no excimer emission peak can be observed for the star PAA molecules. For both polyelectrolytes, the ion specificity is determined by the counterion condensation for the charged chains, whereas the nonelectrostatic ion adsorption governs the specific ion effect for the uncharged chains.Star polyelectrolytes with almost the same arm length but different arm number (2,3,4and6) have been synthesized by ATRP via the "core-first" method by use of different functional initiators. The growth of multilayers using the star polyelectrolytes has been investigated with QCM-D. It is found that the arm number has a significant influence on the chain interpenetration during the LbL deposition. Moreover, the RMS roughness and the static contact angle of the8-bilayer PEM surface are determined by the outmost polyelectrolyte layer.