Control Of Chemical Structure And Morphologies Of Polymer

Polymer materials have been applied extensively in many fields, including space technologies, military industry and so on. It is well known that the properties of polymer materials rely mainly on their chemical structures and morphologies of aggregates. So investigation on control of the chemical structures and morphologies of the aggregates is highly desired. And if the relationships of chemical structures, morphologies of the aggregates with properties of the polymer materials can be established, we will design and prepare the polymer materials with expected properties for special application based on their structures and morphologies.So this thesis focuses on two main projects, control of the chemical structures of polymers and morphologies of polymeric aggregates. And the main achievements are as follows:1) Control of hyperbranched chain growth on both ends of PEO has been achieved in the ATRP of inimer using macro RAFT agent. With this simple and feasible synthetic strategy, the hyperbranched-linear-hyperbranched triblock copolymers have been prepared successively. Principle of this synthetic strategy is interrupting propagation of the hyperbranched chain radicals by transformation active species of their chains onto the functional group of linear PEO, thus propagation of hyperbranched chains is restructed, and the propagation at the end of PEO increases relatively. This provides a convenient method for grafting hyperbranched polymers on the polymer chains or solid material surface.2) Control topological structure of polymers has been achieved simply by tuning feed molar ratio of CuBr to macro RAFt agent in SCVP of inimer. When the feed molar ratio of CuBr to RAFT sites is less than 1, with aid of CuBr/PMDETA, a few of inimer acted as initiator in the RAFT polymerization of inimer, and the linear triblock copolymers with one bromine in each inimer units were produced. For this ratio larger than 1, the initiating sites in PEO chains initiated the SCVP of inimer to form dumbbell polymers. Thus, the topologies of the triblock copolymer can be tuned from linear to dumbbell polymers just by variation of feed molar ratio of RAFT sites to CuBr.3) The atom transfer radical dispersion polymerization (ATRP) of 4-vinylpyridine (4VP) has been carried out in ethanol/H2O mixture. The system displayed two stages of polymerization; the first stage is the formation of diblock copolymer with the polymerization rate of 1.21 mol·L-1·h-1 before 1h polymerization, and the second is the main polymerization in micelles formed from the aggregation of the resultant block copolymers with the polymerization rate of 0.009 mol·L-1·h-1. The Au/polymer composite nanoparticles were successfully prepared by complexation of P4VP with HAuCl4 and following reduction with NaBH4.4) Polymeric nanomaterials with multiple morphologies have been prepared by one-pot RAFT dispersion polymerization. The results of LLS, TEM and FESEM show existence of two phase transitions, the phase separation and re-organization of the formed spherical micelles during the formation of various nanomaterials. The1H NMR and GPC traces evidenced that every transition is related to the growth of the second PS chains, so the phase sparation and the re-organization are induced by polymerization. By appropriately selecting concentration of the monomer and the feed ratio, the uniform nanorods and vesicles have been prepared. The preparation of polymeric nanomaterials can be performed in concentration as high as 0.5 g/mL, this makes the extensive investigations of application possible.5) A facile and feasible approach for preparation of polymeric yolk/shell nanomaterials has been developed via one-pot RAFT polymerization induced self-assembly and reorgnization. The different yolk/shell morphologies could be created and tuned just by varying the ratio of AIBN/P4VP. And the ratio of AIBN/P4VP= 1 is the best condition to prepare polymeric yolk/shell nanomaterials. This strategy is more versatile in comparison with the template methods, and showed great potential for preparation of such nanostructural materials at large scale.