Synthesis And Property Of Block And Graft Copolymers

The structure of the polymer significantly affect the material properties.Block copolymer(BCP)has a linear chain structure and exhibits rich self-assembly behaviors.Plenty of researches on BCPs have been focused on the self-assembly theory,structure control and properties.However,the effects of precisely controlled structures on mechanical properties are fewly studied.Graft copolymer has densely grafted long side chains on the polymer backbone.With the development of polymerization technology,well defined bottlebrush-like graft copolymers have been synthesized,while their properties and applications needs further study.In this thesis,the self-assembly structure and mechanical property of BCP,along with catalystic performances supported by graft copolymers are studied.BCPs with a series of chemical compositions are rationally designed according to self-assembly theory.They were synthesized by anionic polymerization.After a mold pressing process,BCPs show a long-range ordered self-assembly morphology.The cylinders in the sample are uniformly aligned on a micron scale observed by TEM.The mechanical testing of the oriented BCP sample show an obvious anisotropy effect.When the stress is parallel to the self-assembly phase interface,the mechanical response is determined by the hard segment of BCP.When the stress is perpendicular to the phase interface,the material has a reduced modulus.No obvious yield point is found in the strain-stress curve.Graft copolymers are prepared via grafting through method.A combination of atom transfer radical polymerization and ring opening metathesis polymerization are used to precisely control the length and grafting density of the side chains.It is obseved that these bottlebrush polymers have a worm-like configuration by AFM.A series of post modification reactions are used to immoblize phenoxy-imine ligands at the end of side chain.After the coordination of the polymeric ligands with metals,FI catalysts supported by graft copolymers are obtained and used for ethylene polymerization.The polymerization results show that the graft copolymer has little effect on the activity of FI catalyst.However,it has an influence on the molecular weight and crystallinity of polyethylene products,which is probably resulted from the confinment effect of active sites on the polymeric support in the polymerization process.