Synthesis,self-assembly And Friction-reduction Of Organic-inorganic Hybrid Block Copolymers

Organic-inorganic hybrids are a new type of functional materials that integrate the advantages of both organic and inorganic components.The organic and inorganic parts can be combined by non-covalent or covalent bonds.Controlling the contents of organic and inorganic components can adjust the properties of the resulting hybrid materials,leading to most optimal applicability.However,due to the few reactive sites on the inorganic components,the controllable combination of organic and inorganic components is a difficult point.There are few studies on the properties of polyhedral oligomeric silsesquioxanes(POSS)and polyoxometalates combined with polymers to form hybrid materials.In this thesis,a series of organic-inorganic hybrid materials are selected by controllable combination of polymers with different molecular weights and POSS or polyoxometalates.The self-assembly of the hybrids and their friction reduction are studied in detail.This research is divided into the following two parts:1.We have synthesized a series of poly(stearyl methacrylate)(Br-PSMA_2n-Br),and Br-PSMA_2n-Br(2n=14,25,42,60)was further used as macromolecular initiators to synthesize corresponding PPOSS_m-b-PSMA_2n-b-PPOSS_m block copolymers with different POSS contents through atom transfer radical polymerization(ATRP).¹H NMR,GPC,DLS,and TEM experiments were used to characterize and verify the molecular structures of the block copolymers,indicating that the ATRP reaction activity is controllable.The thermal properties of the samples were studied by DSC.The study results found that the Br-PSMA_2n-Br samples were crystalline,while the PPOSS domains in the PPOSS_m-b-PSMA_2n-b-PPOSS_m block copolymers showed crystalline behaviors.This phenomenon was further verified by SAXS and WAXS,and the crystal melting temperatures T_ms of the block copolymers can be adjusted by changing the length ratio of the PSMA and PPOSS segments.The block copolymers were dissolved in base oils and the friction reduction effect was studied.The block copolymer of P3-3 at a low concentration of 0.5 wt%showed significant friction reduction of 60%,which was much higher than that of Br-PSMA_2n-Br being only 20%in the base oils.2.We have synthesized the block polymers of PS_n-b-PDMA_m through two-step ATRP reactions.The block polymers were further ionized by methylation with the PDMA_m blocks.The resulting block ionomers were further exchanged with K₄[?-Si W₁₂O₄₀],leading to the formation of polyoxometalate based hybrids of SDW-1?3.Then,the molecular structures of these polymeric hybrids were characterized by ¹H NMR,GPC,and FT-IR experiments,indicating that the samples were successfully synthesized.The self-assembly behaviors of the samples in THF and chloroform were studied by TEM imaging.The samples were assembled into micellelike aggregates with polyoxometalate cores,and SDW-2 formed vesicles in THF due to both the solvation effect of the PS segments and the solvophobic interactions of the PDMA/[?-Si W₁₂O₄₀]^4-moieties.Moreover,the self-assembly of SDW-1?3 in mixture solvents was studied.As the volume content of water increases in THF/H₂O mixture solvents,due to the hydrophobic effect of the PS segment,the hydrodynamic diameters of SDW-1?3 became smaller in the DLS experiments.SDW-1 and SDW-2 were assembled into spherical micelles in THF/H₂O and chloroform/methanol mixed solvents.And as the contents of water and methanol increased,respectively,polyoxometalate were transferred from the micellar cores to the micellar coronas.In the case of SDW-3,the morphological transition from thin films to spherical micelles were observed as the volume content of H₂O increased.