Research Of One-dimensional Polyemrs And Phototaxic Colloidal Particles Based Hyperbranched Macromolecules

Hyperbranched polymers and the polymer constructs based on hyperbranched blocks have applications in a variety of fields including drug delivery, catalysis and nanotechnology, etc. More and more topological structure based on hyperbranched molecules have been synthesized, such as star, dumbbell-shaped, umbrella-shaped, and worm-like polymer. Non-spherical especially the one-dimensional nanoparticles hold some advantage in many cases in the field of polymer nanocomposites and drugs delivery carrier than their counterpart, namely spherical polymer particles. But synthesis of one-dimensional nanoparticles is usually very complicated.Light-driven microswimmers hold great promise in the field of next-generation drug delivery and micro-robot device. It is desired that the movement of micron particles is not only spontaneous but the direction also controllable, so as to implement their applications.The work described in this thesis is mainly based on the preparation of topological structure derived from hyperbranched molecules, as well as the special properties or functions thereby. The second and third chapter is mainly about preparation of one-dimensional hyperbranched-linking-hyperbranched polymer beads using two different methods. The fourth chapter is about the preparation of the spiropyran terminated hyperbranched polyester, and research the phototaxis property of the colloidal particles assembled by the photochromic hyperbranched polymer. Details included as following:1) We synthesized one-dimensional hyperbranched-linking-hyperbranched beads polymers by using a convenient "one-pot" strategy, namely self-coupling concurrent living polymerization. In this method, the monomer we used was the inimer which could initiate itself to afford hyperbranched polymer. A chain transfer agent cyclic trithiocarbonate served as "hyper linker" to link hyperbranched blocks. The polymerization mechanism and the role of chain transfer agent were investigated. Viscosity characteristics, X-ray diffraction peaks and liquid crystal properties of the resulting polymer showed the one-dimensional ordered features.2) We synthesized one-dimensional hyperbranched-linking-hyperbranched beads polymers by two steps. First, polymerization of the inimer to synthesize hyperbranched polystyrene precursor. Second, making the precursor linked by the coupling agent nitrone. The effect of nitrone to the coupling reaction was studied. Viscosity characteristics, X-ray diffraction peaks and liquid crystal properties of the resulting coupled polymer showed the one-dimensional ordered features.3) We synthesized the first example of fully organic microparticles which could be driven as well as steered by light source. These particles showed a positive phototaxis when they were dispersed and irradiated by UV light, ie, particles moved from all directions to the light source center. The movement trajectory was straight line. The mean-square velocities of the photochromic suspension particles were about 20 μm·s-1, and increase to about 54 μm·s-1 with the addition of NaCl of 0.5%. The phototactic propulsion is supposed to be originated from the UV irradiation-induced interfacial tension gradient on the surface of the colloidal particles. This finding allows for the design of new micro-engines for next-generation drug delivery systems, micro-robotic devices, and self-adaptive photocatalysts, etc.