Synthesis And Properties Of Hyperbranched Polymers Containing Ketone And Fluorene Units

Aldol reaction has been widely used in the area of organic synthesis, but seldom in synthesis of branched or hyperbranched polymer. Therefore, how to apply aldol reaction to polymerization successfully is an intersiting issue. In this thesis, the main content is focused on the application of aldol reaction, by which several types of monomers （AB2, B2 and B₄） are synthesized and further some hyperbranched polyketones are prepared. The main contents of the thesis are as follows.The optimal catalyst is chosen from such catalysts as transition metal catalysts, organocatalysts and Bronsted-Lowry acid/base catalysts. Under the optimum reaction condition several types of monomers are prepared according to ideal graphical synthetic routes. The results show that piperidine acetate is a more efficient catalyst for aldol reaction between aldehyde and acetylacetone than other organocatalysts such as L-proline and imidazolinone. As a consequence, aldol condensation reaction catalyzed by piperidine acetate in an organic solution usually gives a yield over 70%, while in an aqueous solution weak base Na2CO3 is more appropriate than alkali hydroxides （KOH, NaOH） and the corresponding yield nearly reaches 80%.With the optimal conditions, hyperbranched polyketones are synthesized through two different synthetic routes under the same reaction time, and the weight-average molecular weight measured by gel permeation chromatography （GPC） in one-step method is about 104, similar to that in AB2 monomer method. Spectral data from FT-IR and 1H NMR indicate that the polymerization product is aldol adduct. Upon studying its optical properties, a weak, broad-band fluorescence emission at 255-550nm is found, which suggests there may exist some unsaturated segments of a gradient of conjugation lengths in the ideal structure of the hyperbranched polymer.In addition, in an acid solution, another polyketone of A₂+B₄ type is synthesized by aldol reaction with the weight-average molecular weight of 4.6×103. Structural analysis of the polyketone by 1H NMR spectra suggests that reaction mechanism of the polyketone is not exactly in accordance with that of aldol reaction. Meanwhile, its optical properties also show that some unsaturated segments in the polyketone structure results in a weak, broad-band （325-550nm） fluorescence emission. Furthermore, thermo-gravimetry （TG） and differential scanning calorimetry （DSC） are detected at a heating rate of 10℃/min under nitrogen. As a result, a glass transition at 117℃can be observed in the DSC curve, and almost all the weight losses take place in the temperature range of 120⁵50℃.In the fifth chapter, four types of blue-light emitting hyperbranched polymers are obtained by copolymerization of 2,7-bis（4-hydroxyphenyl）-9,9-dialkyl-fluorene（A₂） and pentaery- thritol p-toluenesulfonate（B₄）. All these hyperbranched polymers are characterized by means of UV-Vis and fluorescence spectra. It is found that their spectral characters are similar to that of A₂ monomers, which emits pure and stable blue light. Moreover, the analysis by differential scanning calorimetry（DSC） and thermogravimetry （TG） shows that there exists no phase transition below 150℃and no thermal decomposition below 300℃. This means that all hyperbranched polymers display good thermal stability and controllable luminescent properties.Finally, starting with fluorene and pentaerythritol, two kinds of monomer with fluorene conjugated unit and pentaerythritol star-shaped structure are synthesized, respectively. A blue light-emitting hyperbranched polymer with partially conjugated structure is prepareded through Suzuki coupling reaction. The hyperbranched polymer were characterized by means of UV-Vis and fluorescence spectra. It is found that spectral characters of the hyperbranched polymer are similar to that of the simple model compound of emiting pure blue light. Furthermore, the analysis by differential scanning calorimetry （DSC） and thermo-gravimetry （TG） shows that there exists a glass transition at 136℃and no thermal decomposition below 300℃, which indicates that the polymer has good thermal stability.