Fabrication Of Polyphosphazene Hybrid Particles With Active Amino Groups

Polymerical microspheres bearing amino groups are of particular interests due to their high activity and the instinct of attaching a variety of proteins and biologically active molecules. Dispersion polymerization and blending are the most important methods to fabrication of the active microspheres. However, these two methods either require multi-step approaches or involve the utilization of stabilizing agent for the preparation of the active microspheres. Therefore, the fabrication of polymer microspheres with active amino groups using a simple and surfactant-free method is still desirable. Carbon nanotubes (CNTs) have been paid considerable attention owing to their remarkable mechanical, optical, thermal, and electrical properties. The amino-terminated CNTs are of particular interests owing to their versatile applications including CNTs reinforced polymer composites, biological systems, and electrocatalysis. Generally, two basic strategies have been proposed to produce the amino-functionalized nanotubes: the covalently modification or non-covalent functionalization. The former method often disrupted the intrinsic structures of the CNTs, as a result, leading to the electrical and mechanical properties declined dramatically, the latter often lead to the instability of wrapping. Therefore, there is a need to find new strategies for addressing the objective issues mentioned above. The detail contents are as following: (1) the fabrication of highly cross-linked polyphosphazene microspheres with active amino groups has been successfully accomplished via a one-pot approach. No glass transition temperature and the lack of swelling and dissolution in all of the common solvents indicated the as-synthesized particles were crosslinked. The concentrations of HCCP between 2 to 4 mg/mL were the optimized conditions for the growth of the as-synthesized microspheres. The acylation reaction of active microspheres with benzoxy chloride shows the amino groups possess high activity and can be functionalized. The number of the surface amino groups was studied by FTIR and the result shows that with the molar ratio of HCCP to ODA decreasing, more amino groups can be obtained. The surface terminal -NH2 groups from the functional monomer will allow coupling of a wide variety of active molecules, which make the microspheres having potential applications in chemical industry and functional materials.(2) the MWCNTs-based composites have been successfully synthesized via layer-by-layer self-assembly of crosslinked polyphosphazene nanoparticles on the surface of MWCNTs. Compared with traditional noncovalent methods, this novel strategy would make the interfacial interactions between wrapping polymer and carbon nanotubes more stronger, because each reactive nanoparticle play a chemical-crosslinking-sites role in three-dimensional space located in the wrapping shells. The amino-terminated CNTs were characterized by XPS, FT-IR spectroscopy, EDS, XRD, and TEM. The degree of functionalization could be controlled by simply changing the mass of hexachlorocyclotriphosphazene (HCCP) with 4, 4-diaminodiphenyl ether (ODA). The activity of the surface amino groups was confirmed by the reaction of these groups with chloroauric acid (HAuCl4). In addition, the effects of the mass of HCCP and ODA ratios on the content of the surface amino groups was also discussed. The thickness of wrapping polymer and the number of amino groups could be controlled by simply changing the mass of HCCP with ODA. Result from immobilization of Au nanoparticles on the amino-terminated CNTs surface confirms that the amino groups possess high activity and can be further functionalized. The unique nanostructures are expected to explore the following potential applications: a) acting as chemical crosslinking agents embed into polymer matrix for reinforcing composites; b) coupling of a wide variety of biological molecules for biological application; c) immobilization of some noble metals for the optical and electrocatalytic properties.