| Polysilane is a class of conjugated polymer which is composed of Si-Si main chain and organic side groups. Due to the lower electronegativity of Si atom and its unoccupied3d orbital, the σ electron of polysilane can delocalize along the main chain widely, thus providing electronically analogous properties to the π-conjugated polymers. The delocalization of polysilane can make the σ transition happen easily as a result of lower excitation energy and induce a fluorescent emission in UV region or visible light region, which make it has the potential application in light emitting diodes (LED) and non-linear optical materials.This article summarized lasted research advances of polysilane at home and abroad and combined it with the recent attracted researches on the POSS modified optoelectronic materials. Then, two kinds of POSS functionalized linear and branched (starlike) polysilanes were designed and prepared, and the effects of the introduction of POSS on the optoelectronic properties of polysilane, especially the fluorescence quantum efficiency and stability, were also discussed.The mono-vinyl-POSS was synthesized by cohydrolytic and cocondensation reaction and the mono-methyl-β-ethyl-dichlorasilane-POSS was synthesized by hydrosilylation reaction. Then, a serious of linear polysilanes with POSS as side groups were prepared by Wurtz coupling reaction through varying the feed ratio of chloral-containing POSS monomer and MePhSiCl2.The octa-methyl-β-ethyl-dichlorasilane-POSS was synthesized by hydrosilylation reaction and two kinds of Si-OH end-capping linear polysilanes were prepared via Wurtz coupling reaction. Then, two kinds of branched (starlike) polysilanes were obtained by the condensation reaction of Si-Cl and Si-OH of two products by the removal of HCl.The structures of synthesized products were investigated using FT-IR and1H-NMR, and the molecular weight and molecular weight distribution of polysilanes were observed by GPC. The aggregation structures of polysilanes were studied using XRD and the results showed that the introduction of POSS reduce the crytallinity of polysilane molecules, therefore endowing them a better solubility. The UV absorption properties of polysilanes were investigated by UV absorption spectra. The results indicated that the incorporation of POSS into the polysilane will not change molecular orbital energy levels or change it slightly. Furthermore, for linear polysilanes, when the number of POSS side groups attached on main chain increased, the UV resistant stability of polysilanes was increased accordingly. However, for branched (starlike) polysilanes, it possessed a superior UV resistant stability—without any degradation with an increase of radiation time.The fluorescent emission properties were studied using fluorescent emission spectra, and combined with the UV absorption spectra, the relative fluorescence quantum efficiency of them were also calculated. The results showed that for linear polysilane, with a decrease of POSS content,ΦLa:ΦLb:ΦLc:Φ0=1.92:1.33:1.19:1.03:1; for branched (starlike) polysilanes, ΦB1:ΦL1=5:1.The thermal stabilities of polysilanes were tested by TGA. The results demonstrated that they possessed an excellent thermal stability and had a degradation above320℃. For linear polysilanes, by tuning the number of POSS side groups, the starting decomposition temperature can pass370℃; for branched(starlike) polysilanes, they also have a high mass remains, always over60%, thus making them become a promising candidate in the SiC ceramic industry.In summary, this class of POSS-containing linear or branched(starlike) polysilanes can obviously improve the fluorescence quantum efficiency and stabilities of polysilanes, therefore providing an excellent optoelectronic properties. |
PDF Full Text Request