The Synthesis And Characterization Of Dendritic Azo Liquid Crystal MacroMolecules

Dendritic liquid crystalline macromolecules show a great potential application prospects in functional materials, such as, reversible optical information storage materials, nonlinear optical materials, ferroelectric liquid crystal materials, electro optical displaying materials and so on. In this paper, a novel kind of dendritic polyamidoamine was designed and synthesized, and two kinds of azo liquid crystal molecules were grafted to the end capping to get two kinds of dendritic liquid crystalline macromolecules. At present, the target dendritic liquid crystalline macromolecules are not seen in the related report.First, we demonstrated a series of novel dendritic polyamidoamine (PAMAM, GO.5, G1.0, G1.5and G2.0), which using ethylene diamine tetraacetic acid (EDTA) as the initiated core for the first time were successfully synthesized step by step divergently, namely an amidation of carboxyl group with ethylenediamine (EDA), followed by exhaustive Michael addition of amino groups with methyl methacrylate (MMA). The influence of reaction conditions of syntheticing PAMAM dendrimers (eg. reaction temperature, reaction time and feeding molar ratio) to get a higher yield were discuessed, the synthesis of GO.5was controlled at room temperature for24h. dicyclohexylcarbodiimide (DCC) was used as dehydrating agent,4-dimethylaminopyridine (DMAP) was used as catalyst, kept the ratio of EDTA and EDA at1:24. we found the productivity of GO.5reached98.1%. The synthesis of G1.0was controlled at40℃for24h, kept the ratio of CEDTA-0.5G-PAMAM and MMA at1:16, we found the productivity of G1.0reached85.7%.The synthesis of G1.5was controlled at25℃for24h, kept the ratio of CEDTA-10G-PAMAM and EDA at1:40.The synthesis of G2.0was controlled at40℃for24h, kept the ratio of CEDTA-1.5G-PAMAM and MMA at1:32. Sixteen end ester groups were got in the G2.0dendritic polymers. The structures properties of these dendrimers have been investigated by FT-IR.1HNMR.Secondly, two kinds of azobenzene molecules (LC1and LC2) were successfully synthesized with aniline, p-nitro aniline as diazotization components, respectively with aniline, by coupling reaction. The structures of LC1and LC2were characterized by FT-IR:TG indicated that the thermal stability of LC1and LC2was good; UV showed a good response of the LC1and LC2in the range of230-600nm for UV light; LC, and LC2had a good light induced isomerization proerties for monochromatic excitation of365nm light; The photochromic response time of LC1and LC2/Rare190s and34s; In conclusion, LC1and LC2was suitable for light induced isomerization materials.Final, two kinds of azo liquid crystalline PAMAM (2.0G PAMAM-LC1and2.0G PAMAM-LC2) were synthesized by end capping reaction of azo-benzene liquid crystalline units (terminal groups contain-NH2, LC1and LC2). The structures of2.0G PAMAM-LC1and2.0G PAMAM-LC2were characterized by FT-IR; TG indicated that the maximum decomposition temperature of2.0G PAMAM-LC1and2.0G PAMAM-LC2was above100℃, showed that it had ordinary thermal stability;2.0G PAMAM-LC1and2.0G PAMAM-LC2were indicated thermotropic nematic liquid crystalline polyurethane by POM and XRD.