Controllable Fabrication Of The Multiform Polyphosphazene Micro/Nano-Materials

With the rapid development of science and technology, more and more attentionis focused on the organic-inorganic hybrid polymer material in the micrometer ornonometer size based on their superior properties and wide application.Polyphosphazene material is one of the most important inorganic materials after theorganosilicon materials. Because the phosphorous-nitrogen bonds are extremelyflexible due to the low torsional energy and a large variety of side groups,polyphosphazenes can be made with a wide range of chemical and physical propertiesin the linear phosphzene domain. Phosphazene-containg polymers, which showexcellent thermal stability, biocompatibility and biodegradability, have been appliedin many domains such as in biomaterials, semiconductors and photoelectric materials.Crosslink polyphosphazene materials, as one novel domain, also have made positiveprogress in the scientific research and application domain. Crosslink polyphosphazenematerials with different morphologies, good thermal and other properties are reportedby our group, and based their unique properties, more high-tech applicationsexploration woule be explored in the near future.The previous researches on the crosslink polyphosphazene material by our groupare most focused on the reaction between the hexachlorocyclotriphosphzene (HCCP)and monomer with two benzene rings and double functional group system, such as4,4’-sulfonyldiphenol,4,4’-(hexafluoroisopropylidiene)diphenol and4,4’-diaminodiphenyl ether. The reaction products show good thermal stability andpotential application in the biological medicine, super hydrophobic material,fluorescence biomarkers, and so on. However, some weak bonds exist in the polymerand the uniformity of the microspheres was difficult to control. To enlarge thecrosslink polyphosphazene reaction system and explore the reaction principle, the reactions between HCCP and the monomer with single benzene ring and two or morefunctional groups, such as resorcinol, hydroquinone, amino-phenol, phloroglucinol,potassium2,5-dihydroxybenzenesulfonate, are researched by different reactioncondition. By controlling the different condition, we can prepare monodispersedand functionalized polyphosphazene material. In this paper, we mainly introducethe crosslink reaction between HCCP and phloroglucinol. Under the optimumcondition, we can prepare the monodispersed microspheres with superior thermalproperty and intrinsically fluorescent property. By deeper research, one novelbowl-shape microsphere is successfully prepared by a facile solvent treatment andthis is rewarding for the principle research of crosslink polyphosphazene. Thedetailed contents are as follows.(1) In the reaction system with HCCP and phloroglucinol as comonomers,triethylamine (TEA) as acid-acceptor, and acetonitrile as solvent, an optimumcondition for preparing poly(cyclotriphosphazene-co-phoroglucinol)(PCTP)microsphere was obtained through checking the influence of different conditions suchas preparation methods, ultrasonic power, temperature, concentration of monomer, onthe morphology of as-synthesized product. By controlling different conditions, we canprepare the monodispersed microspheres with diameter with600nm~1100nm byadding the monomer to the solution in one time. When the monomer concentration isensured, the temperature and ultrasonic power have little influence on the size of themicrosphere. The monomer concentration is the major factor to affect the size of theprepared polyphosphazene microsphere. With the increase of monomer concentration,the size of the microspheres increased gradually, which accords with the oligomericspecies absorbing mechanism. The thermal and optical tests indicate that the preparedPCTP microspheres have superior thermal stability, broad and high intensityultraviolet-visible absorption and fluorescent stability. All the superior properties mayresult in potential applications in ablation-resistant materials, solar energyphotoelectric materials and biomaterials, etc.(2) The prepared polyphosphazene microsphere by HCCP and phloroglucinolwas proved to be solid. After the post-treatment to the microspheres by acetone, as reported in this paper, we successfully prepare hollow bowl-shaped polymericstructures by a facile solvent-treatment process, and they are proven to be uniformwith a shell thickness of about120nm. To the best of our knowledge, this is the firstreport to obtain a hollow bowl-shaped polymer based on polyphosphazene. A possiblemechanism is proposed for the formation of the hollow bowl-shape structure asdetermined by scanning (SEM) and transmission electron microscopy (TEM) andatom force microscopy (AFM) observations, combining with the carbonizationexperiment result and XRD analysis which indicates the core of the PCTPmicrosphere is composed of oligomers without inorganic species. In this paper, anappropriate solvent, treatment time, and wide PCTP concentration are investigated.By SEM and TEM observations of the preparation of the PCTP microspheres and theformation of the bowl-shape structure, a preliminary oligomers-swelling principle forthe change is suggested. The products are envisoned to have promising applications inmicroreactors to fabricate functional composite particles, in catalysis, or thebiomedical domain.