| With the rapid development of polymer science and industry, people areincreasingly demanding high-performance materials, the ordinary common plasticscan not meet the application of high-end products. Thus, organic-inorganic hybridpolymer materials which have advantages of machine materials and inorganicmaterials are widely researched by scientists, especially polysiloxanes, polysilanes,and polyphosphazene polymer.In recent years, there has been considerable interest in the polyphosphazenefamily of materials because they not only have a wide range of thermal and chemicalstabilities but also the surface of this polymer can be modified by interfacial reactionsto link functional groups and biologically active molecules to the interface. The bestknown phosphazene materials are linear polymers with an alternating P-N backbonesynthesized by the ring-opening polymerization of hexachlorocyclotriphosphazene, and these have been extensively studied for applications as solid polyelectrolytes,biomedical and metallorganic polymers, and flame-retardant materials. However, theirmain disadvantage, in further widening the application of linear polyphosphazenes, istheir low yield and high cost. Other kinds of phosphazene materials, having longattracted attention, are cyclolinearand cyclomatrix-type polymers, in whichphosphazene rings are linked via exocyclic groups to form linear chains or acrosslinked matrix. More research has been focused on the generation of cyclomatrixmaterials because the complexities involved with the synthesis of cyclolinearmaterials severely limit their desirability.In past decades, a series of phosphazene cyclomatrix polymers have beenreported, and they are used in adhesives, flame-retardant polymeric additives, andthermoset resins for their high thermal stability. Most of these cyclomatrix polymersare synthesized in two or more complicated steps: a bifunctional compound, such ashydroquinone or amino-phenol, is attached to a phosphazene ring first, andsubsequently, the obtained precursors are cross-linked with other bifunctionalcompounds, such as compounds with anhydride and carbonyl chloride groups. It ishard to prevent a chain extension reaction thoroughly in this process, and it is likely toresult in defective structure formation in the final cyclomatrix products. Therefore,one active group of the bifunctional component must be protected first and thendeprotected to form a distinct cyclic trimer, which complicates the reaction procedureand limits its applications.Previously, it was reported that ionically cross-linked polyphosphazeneshydrogel microspheres were prepared by ionic complexation, which can be used forprotein encapsulation. The preparation of polymorphic poly[cyclotriphosphazene-co-(4,4’-sulfonyldiphenol)] nanotubes via an in situ template approach and silvernanocables wrapped with hybrid poly[cyclotriphosphazene-co-(4,4’-sulfonyldiphenol)]via a hard-template approach. All these results indicated that polyphosphazenepossessed special potential in the fabrication of molecular-level inorganic-organichybrid micro-and nanoscale materials. However, the functionalization of thosematerials has less been studied. Therefore, the study on the functionalization of hybridinorganic-organic materials appears to be extremely necessary and may offer newopportunity for their further applications.Herein we present a facile, general, and effective protocol for the one-potsynthesis of surface-functionalized novel cross-linked polyphosphazene-aromatic ethers organic-inorganic hybrid microspheres by a single-step precipitationpolymerization. Our approach allows the direct one-pot synthesis of series functionalpolyphosphazene microspheres. To the best of our knowledge, this is the first reporton these polyphosphazene-aromatic ethers microspheres and also the first time toinvestigate the morphology of different structures of polymer chain. Unlike thepreviously report, we focus on the influence on oligomeric species-absorbingmechanism of different side groups. The morphology and particle sizes, the structureof polymers, and hydrophobic properties of the resulting microspheres werecharacterized.Thesis is divided into two parts: one is the synthesis and characterization ofmonomer and polymer, the other is the study of morphology and absorbingmechanism of different structures of polymer chains.A series of full cross-linked polyphosphazene micro-nano spheres have beenprepared via the polycondensation between hexachlorocyclotriphosphazene,(HCCP)monomer in the presence of TEA by precipitation polymerization. cross-linkedpolyphosphazene micro-nano spheres have been well characterized by means of SEM,FTIR, TEM and DSC. No glass-transition temperature was observed for themicrospheres, implying that the particles consisted of fully cross-linked, insoluble gel.By changing the experimental conditions, such as concentration of HCCP andultrasonic power, the particle size of the polymer micro-nano spheres can becontrolled. The Dn of the micro-nano spheres increased with the increasingconcentration of HCCP; the Dn of the microspheres changed significantly with theincreasing ultrasonic power. The formation of non-porous microspheres was observedto obey an oligomeric species absorbing mechanism. In addition, the onset of thethermal-degradation temperature was336oC. From the DSC and TGA data, themicrospheres have excellent thermal stability. The results show that: novelcross-linked polyphosphazene-aromatic ethers organic-inorganic hybrid microsphereswith different structures. The formations between flexible chains and rigid chains ofspheres corresponded to distinct oligomeric species-absorbing mechanisms. Thedifferent formations of different structures of spheres corresponded to distinctoligomeric species-absorbing mechanisms. The wettability of the different structures’sphere surfaces was caused by the different atom on the spheres surfaces. This resultindicating that the spheres may have potential applications as hydrophobic material. In summary, the forming process of the micro-nano spheres obeyed an oligomericspecies absorbing mechanism as proposed by Choe and coworkers. At the initialperiod of the precipitation polymerization, primary stable micro-nano spheres aregenerated through the aggregation of the primary nucleus particles. Once the stableparticles are generated, the particles grow in size by absorbing oligomeric speciesinstead of primary particles. Therefore, pores do not exist in the micro-nano spheresobtained at the end of the polymerization. It is noted that the initial nucleus aregenerated by precipitation of the cross-linked oligomeric species, only when themolecular mass of the oligomeric species are beyond a critical value (criticalmolecular weight M w.c). The performance of materials depended on its macro-andmicro-structure design. |
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