Synthesis, Structure And Self-assembly Of Star-like Supramolecular Polymers Comprising Inorganic Core

Star-like polymer is a kind of branch polymer, with one core and more than3radical arms around. For such a special molecular structure, it always displays somespecial physical or chemical properties compared with the same molecular weightclassic polymer, such as viscosity, hydrodynamic volume, diffusivity, self-assemblybehaviors etc. For such differences, the star-like polymer displays huge potentialapplications in the areas of optics, catalyst, medicine and self-cleaning materials etc.The developing tendency of star polymer shows three obvious features: the forcebetween the core and arms turning from covalent bond to noncovalent bond; thecompositions turning from pure organic polymer to organic-inorganic hybrid polymer;the functional characteristics turning to realize the synergistic effect of arms and core.So it is very important and valuable to introduce the functional nanoparticles intostar-like polymers to build functional materials.Polyoxometalates (POMs) are a kind of clusters with regular structures andvarious topologies. Their skeleton structures are formed by early transition metaloxide through different kinds of oxygen bridges. They always display goodperformance in medicine, optics, electrochemistry and magnetism etc. For they belongto inorganic category, they also have some weaknesses of them, such as poorprocessibility, high lattice energy etc. Those disadvantages limit their applications in broaden field.Recently, In order to overcome those problems, many methods have been used tomodify POMs. Generally, there are two methods: one is connecting POM with organicparts by covalent bond; the other is connecting the organic parts with POM byelectrostatic interaction. The first one is only suitable for some kind of special POMclusters, while the other one is a general and easier method.While how to introduce POM into specific positon uniformly and realize theproperties of POM well are still big problems for recent researches. Synthesis oforganic-inorganic hybrid star-like polymer is not only a general and effective methodto solve this problem but also can broaden the scope of star polymer.So in this dissertation, we synthesized POM-cored hybrid star-like polymer byintroducing RAFT agents onto POM and carried out polymerization with styrenemonomers. We studied the self-assembly behaviors of them in solution/film andair/water phase. Further on, we also studied the co-assembly behaviors of them withamphiphilic block polymer. There are mainly three parts of work:1. We encapsulated [EuW10O36]9which possess of good luminescence propertieswith RAFT agent containing surfactant BPDA, forming thesurfactant-encapsulated-polyoxometalate (SEP). The SEP is a kind of complex with9BPDA around one POM molecule. By changing the molar ratio of SEP and styrenemonomer, we can obtain a series of star-like polymers (EuW10-PS). According to theTEM images of star-like supramolecular polymers (SSPs) after stained by RuO4, wefound the SSPs are monodispersed in CHCl3solution, and their diameter increasedwith the molecular weight increased; according to the SAXS results we can see thatthe distance between the POM clusters increase regularly with the molecular weightincreased; the DSC results suggested that the Tg also increased with the molecularweight increased from66oC to101oC; the PL spectra of SSPs suggested that thecolor purity of POM also changed regularly with the molecular weight increased;according to the electrospinning experiment of SSP-120, we know that the SSPpossess of good machinability as the traditional polymers. So through this part of work, we got a general method for synthesis of SSPs on POM and an easy method tocontrol the self-assembly behaviors and properties of SSPs whatever in solution, filmor the air/water phase.2. In this part of work, we encapsulated the ball-like keggin type POMK6CoW12O40with surfactants named BPTA, which is a kind of single chain RAFTagent, and get the SEP (BPTA-CoW12). Carried out polymerization with different ratioof styrene monomer, we can get a series of star-like supramolecular polymer (SSPs)with low molecule weight distribution and regular structure. By the “breath figure”method, we prepared the honeycomb structured films used the SSPs, according to theresearches of influenced conditions for film formation; we got the best condition forthe SSPs forming honeycomb structure films. According to the SEM images of theporous film prepared from SSPs and SEP at the same molecular weight, concentrationand different air flow rate, we found that we can get the good film at400mL/min;according to the SEM images of them at the same air flow and molecular weight, wefound that at the concentration of6mg/mL, we can get the good film with SSPs; fixedthe condition at400mL/min and6mg/mL, we found the SSP-3is more easily to formordered honeycomb structure film. From the cross sectional images of them, we cansee that the films formed with SSPs are similar as molecular sieve. Poured the TiO2gel into the porous membrances by sol-gel method, we got the multistage TiO2porousmembrances films after removed the templet.3. Using SSP-2, SSP-3, SSP-4as the nanofiller, we studied the co-assemblybehaviors of SSPs and amphipathic block polymer PS384-PEO863(BC) in solutiondriven by enthalpy. According to the researches, we got a series of morphologies frommicelle, rosary, toroidal to bicontinuous. We can control morphology transition byadjusting the molecular weight and molar ratio of the SSPs. According to the TEMimages we know that even the smallest SSP can induce the POM dispersion in the PSregions uniformly. We discovered an unconventional mechanism for forming toroidalstructure, sphere-rosary-toroidal in our experiments for first time. We also simulatedthe co-assemble behaviors of BC and POM-based star-like polymer after switched off all charges on POM and BPTA by computer, only micelle structure was obtained. So itsuggested the electrostatic interaction is very important for self-assembly behaviors ofBC and star-like polymers.Conclude our work: we got a series of SSPs through carried out in-situ RAFTpolymerization on POM with different structures or properties. Then we studied theself-assembly behaviors of SSPs in solution, film and air/water phase, and theco-assembly behaviors of SSPs with amphipathic block polymer in solution. Westudied the co-assembly behaviors of SSPs and BC by combination of theoreticalcalculation and experimental method. All those researches are important for SSPsstudies on the areas of synthesis, measurement methods, property modulation andsynthesis of new materials.