Synthesis, Microstructure And Dielectric Property Of Functional Polynorbornene Derivatives

Nowadays, ring-opening metathesis polymerization (ROMP) has been studied in the field of materials science, such as liquid crystal materials and nonlinear optical materials, however, the research towards materials area is relatively rare. Therefore, it is essential to expand the research of metathesis polymers in the field of materials. When ROMP of monomers occured, the unsaturated carbon-carbon double bond could remain in the main chain of polymers, constituting its unique microstructure, such as trans/cis ratio of double bond and tacticity. A variety of functional polymers can be easily obtained by the introduction of functional side group to norbornene and single microstructure polymers can be obtained by using specific catalyst and monomer, which could greatly improve the performance of the polymer materials.Materials with high dielectric performance are ideal for fabricating thin film capacitors. Having a high dielectric constant is the basic requirements for the minimization of film capacitor devices. The common high dielectric materials include inorganic ceramic and organic/inorganic composite materials, but the dielectric loss is large and the processing of materials is very expensive and complicated. Thin film capacitors based on polymers have attracted a great deal of attention for energy storage applications due to their desirable properties, such as lightweight, low dielectric loss, and safety. However, these polymer film capacitors generally suffer from low energy density because of a low dielectric constant (2-6). Therefore, it is of great significance to develop polymer materials with higher dielectric constant.In this dissertation, we have designed norbornene derivatives with large dipolement groups to obtain polymer materials with high dielectric constant via ROMP. The characterization of the dielectric constant indicated the relationships between the microstructure of polymer chains and the properties of materials. And further investigation on the impact factors to the microstructure of polymer chain, such as monomer configuration and catalyst. Firstly, we have designed and synthesized the functional endo,endo-norbornene dicarboximide (endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-dicarboximide, endo-TNDI) and corresponding pyrrolidine monomers (endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine, endo-TNP and endo-N-phenyl-norbornene-pyrrolidine, endo-PNP). Grubbs catalysts were selected as the catalyst for ROMP reaction of monomers.13C-NMR has been used to characterize the microstructure of polymer chains, and found that endo.endo-norbornene-pyrrolidine-based polymers had relatively higher trans double bond and better tacticity. Among them, endo-PTNP adopts isotactic stereochemistry, which have practically trans double bond and the dipolar pendant groups are coherently arranged in the syn conformation. endo-PPNP may be isotactic anti or syndiotactic syn and anti conformations. By contrast, endo-PTNDI is supposed to be atactic, which is in accordance with trans and cis isomers. endo-PTNP has a much more higher dielectric constant about20than that of endo-PPNP about3. And endo-PTNDI, its dielectric constant decreased to about7, although bearing two CF3groups in each TNDI unit. TGA, DSC showed that all of these norbornene-based polymers have good thermal properties.Secondly, on the basis of above results, by changing the configuration of the monomer has been considered. We have obtained exo,exo-bis(trifluoromethyl)biphenyl-contained norbornene dicarboximide (exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-dicarboximide, exo-TNDI) and pyrrolidine (endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine, exo-TNP) monomers. When the Grubbs catalysts (Ru-I, Ru-II and Ru-III) were used, the polymerization of exo-configuration type monomers exhibit a much higher reactivity. The trans/cis ratio of synthesized polymers has been analyzed by integration of the13C NMR signals and IR. Polymers obtained from Ru-I have trans/cis ratio of83%:17%and67%:33%, and Ru-III catalyzed ones have trans/cis ratio of50%:50%and30%:70%, indicating the affection by the composition of catalysts on the trans/cis ratio of double bonds in the polymer backbone. As we obtained the isotactic endo-PTNP(Ru-â… ), further study on the polymerization of endo-TNP by using different catalysts (Ru-â…¡, Ru-â…¢) was carried out, expecting to investigate how the catalyst would impact on the microstructure of polymers.13C NMR is also employed to analyze the microstructure of the polymer chains. The results showed that polymers with exo-configuration and endo-PTNP(Ru-â…¢) had lower tacticity. The results of dielectric properties of polymers with lower tacticicty of microstructure show that the dielectric constant of exo-polynorbornene derivatives are in the range of6-9. At the same time, we have synthesized the acrylamide-based polymers (PTAA) with the same side groups as the norbornene-based polymers, and the dielectric constant of PTAA is only5-6.5. Moreover, the results of DSC measurement show that the thermal property of polymers has a dependence on their translcis ratio.