The Synthesis And Properties Of Organosilicon Polymers Via CuAAC Click Chemistry

The Cu(?)-Catalyzed Azides and Alkynes Cycloaddition (CuAAC), which is defined as "Click Chemistry", has been intensively applied in polymer synthesis since its discovery by Sharpless and Meldal groups in 2002. This kind of reactions exhibit a lot of advantages, including benign reaction conditions, simple workup, high tolerance of functional groups, insensitivity of solvents and quantitative yields. So the powerful and efficient synthetic method has gained popularity in polymer synthesis and material science over the last decade.The?-?conjugated organosilicon polymers containing alternated organosilicon and?-conjugated units have been attracted much attention. In such polymers, the 3d-orbital of silicon atoms can change electron delocalization of the?-electron segments to suggest?-?interaction. So the?-?conjugated organosilicon polymers will exhibit unique optical properties, and their processability and solubility can also be improved due to the flexible silicon linkers. Therefore, the?-?conjugated organosilicon polymers can be potentially applicable to organic light emitting devices (OLEDs), electroluminescent display, semiconductors, optical sensor and ceramic precursors. As we know, most of the?-?conjugated organosilicon polymers are made by polycondensation of powerful coupling strategies, such as Suzuki reaction, Stille reaction, Heck reaction, Sonogashira reaction, Hydrosilylation and so on. But expensive metal catalysts and extreme conditions are always required in the above mentioned reactions, which limit the development of the?-?conjugated polymers.Base on the above discussion, we attempted to take the advantages of CuAAC Click chemistry introduce the facile and reliable reaction to synthesize the?-?conjugated organosilicon polymers.First of all, Poly[silylene-(1,2,3-triazol-4-yl)-1,4-phenylene]s (P1-P3) have been prepared via CuAAC Click step-growth polymerization from diethynylsilanes and 1,4-diazidobenzene. The Click coupling reaction was carried out in DMF/pyridine mixture using Cu?as a catalyst. The same catalysis conditions is used to synthesize Poly[silylene-methylene-(1,2,3-triazol-4-yl)-1,4-phenylene]s (P4). The UV-visible spectra of polymers show almost identical absorption at around 270 nm. The absorption of P4 is ca.10 nm red-shift compared to that of P1-P3. The results indicate that the silylene group not only hehaves as a electron insulator like methylene group, but also influences the UV-vis absorption by the electronic transitions between the silylene and?-conjugated units. On the other hand, the compound M1, whose structure is close to one repeating unit of the polymers, displays similar absorption with P1-P3. The polymers fluorescence emission in CHCl3 solutions were observed as similar broad band in visible blue region (ca.430 nm). M1 emits shoulder peak at 415 and 435 nm, and no obvious wavelength shift is observed. However, P1-P3 exhibit stronger emission than M1, and the quantum yields (0) of P1-P3 were ranged from 0.19 to 0.37, is higher than that of M1 (only 0.09).We prepared Poly[silylene-1,4-phenylene-(1,2,3-triazol-4-yl)-1,4-phenylene]s (P5, P6) by step-growth Click polymerization of bis(p-ethynylphenyl)silanes and 1,4-diazidobenzene. The Click coupling reaction was also carried out in DMF/pyridine mixture using Cu?as a catalyst. In order to understand the nature of the polymers, two model compounds (M2, M3) were synthesized. The absorption of the phenyl unit in M3 is ca.15 nm red-shift compared to that of M2. So the red-shift can be ascribed to the?-to-?charge transition between phenyl and silylene units. No obvious wavelength shift is found between the polymers and M3. The emission maximum of the polymers and M3 in CHCl3 solutions are observed at around 440 nm, while the emission maximum of M2 is 461 nm. the emission maximum wavelength of silicon-containing compounds is about 20 nm blue-shifted compared with that of M2, which can be attributed to charge transition between the silicon atoms and aromatic rings. no obvious emission wavelength difference between M3 and the polymers was observed, which illuminate the charge communication is not strong enough to connect the whole backbones of the polymer and only partial?-?conjugation occurred along the main chain. The relative intensities of the polymers were stronger than that of M2 and M3 due to the polymeric structure. The quantum yields (?) of P5 and P6 were 0.45 and 0.47, higher than that of M2 and M3. The emission intensity and quantum yield (?) were enhanced due to the influence of?-?interaction. The results of the absorption and emission supported the weak?-?conjugation between the silylene and aromatic segments.We synthesized two series of?-?organosilicon polymers via Click step-growth polymerization. The above results illuminate the silicon atom can influence the electron delocalization of the?-electron segments, but the electronic transitions is not strong enough to connect the adjacent?-conjugated units, and only weak?-?conjugation occurred along the main chain. The present results provided a reliable and cheap method to modify the solubility, processability and optical properties of the?-conjugated polymers. The obtained novel?-?conjugated organosilicon polymers was observed in visible blue region (ca.430?440 nm) in the fluorescence emission spectrum. The emission intensity and quantum yield were also enhanced due to the?-?interaction of the polymer main chains. Therefore, these polymers could be used as potential optical materials in OLEDs.Polysiloxane is the most useful polymers in organosilicon chemistry. The main chain of polysiloxane is composed of Si-O groups as repeated units, and some different organic units are introduced in the side chains. The Si-O band is very flexible, and band energy is relatively high, so the polysiloxane exhibit a lot of advantages, including heat/frozen resistant, chemical reagents resistant, enviroment resistant and fire resistant, so the polysiloxane can be widely used in building, medicine, electronics and space science.On the other hand, the polysiloxane can exhibit more advantages when some functional groups were introduced to the side chain. But the general method to prepare functional polysiloxane is the Hydrosilylation. Similarly, the Hydrosilylation require expensive Platinum or Rhodium catalysts, and the protection and deprotection are required in the preparation of polysiloxane with -OH,-NH2 and other active proton groups, and isolation of humidity and oxygen are always required. So we try to introduce the CuAAC Click chemistry to modify the polysiloxane. The facile and reliable method can be used to synthesize functional polysiloxane without expensive catalysts and extreme measurements. First of all, the chloropropyl polysiloxane was synthesized, and then the azidopropyl polysiloxane can be obtained via the simple nucleophilic displacements with sodium azide directly. Finally, the different functional polysiloxane were obtained after the Click reaction of alkynyl compounds and azidopropyl polysiloxane.