Synthesis Of Azo Polyamide And Their Study On Photochromic Properties

Because of their unique photochromism of azobenzene and good mechanical propertiesand processability of polymer materials, azobenzene polymers have potential applications inoptical switching, optical data storage, electrooptical modulators, nonlinear optical materials,liquid crystal maerials, nanophase materials and so on. They have attracted much attentionin the past few years. In this dissertation, according to the application in optical data storageand optical molecular switching of azobenzene polymers, two different kinds of polymerscontaining azobenzene which were linear azo polyamide(LAPE) and hyperbranched azopolyamide(HBAPE) were designed and synthesized. The synthetic technology, structure andproperties were studied in systematically. The main results obtained of this study were listedas below:(1) A series of LAPE and HBAPE with different proportions were synthesized, andtheir structures were confirmed by FT-IR、1H-NMR、13C-NMR and GPC. All the factorswhich might affect molecular weights of LAPE and HBAPE were tested, and the optimizedfactors were found. The optimized synthesis conditions for LAPE were the AZDAconcentration of 0.45mol/L, polymerization temperature of 80 oC, reaction time of 4h,Li Cl amount of 0.06g/m L and monomer molar ratio( SUNC: AZDA) of 1.2:1, respectively.The largest Mw and D were 4.0×104and 1.60. Meanwhile, the optimized synthesisconditions for HBAPE were the AZDA concentration of 0.25mol/L, reaction time of 12 h,Li Cl amount of 0.35mol/L and monomer molar ratio( BTC: AZDA) of 1:1, respectively.The largest Mw and D were 4250 and 1.70.(2) In comparison with 4,4’-Azodianiline(AZDA), LAPE and HBAPE had poorsolubility. But the solubility of HBAPE was much better than LAPE, which fullydemonstrated characteristic of high solubility of hyperbranched polymers. The data of TGAshowed that both LAPE and HBAPE possessed good thermal stability.(3) AZDA、LAPE and HBAPE displayed trans-cis photoisomerization upon irradiationat 365 nm and cis-trans back-isomerization with heating or visible light. Under the sameconditions, for AZDA、LAPE1 and LAPE4, the reaction rate of trans-cis isomerization ofLAPE4 with less amino was the largest and decreased with increasing polarity of theorganic solvents, and the thermal and light back isomerization rates were least, theirradiated solution returned to original state after 72 h in the dark at room temperature. ForAZDA、HBAPE2 and HBAPE5, because of highly branched structure, the reaction rate oftrans-cis isomerization of HBAPE2 with more azobenzene was the largest and the thermaland light back isomerization rates were least, the thermal back isomerization rate increasedwith increasing of temperature. After 48 h in the dark at room temperature, the irradiatedsolution returned to original state. Meanwhile, in comparison to LAPE2, the trans-cisphotoisomerization rate of HBAPE2 was larger, which indicated that the synthesizedhyperbranched polymers exhibited better optical response properties and might bepromising candidates as optical storage medium materials.(4) In THF solution, both LAPE4 and HBAPE2 possessed better reversible opticalproperty and lower energy consumption, which exhibited favorable fatigue resistance. Andthey two had sensitive recognition ability to OH-1and showed good selectivity.(5) The variation of fluorescence emission spectra curves of AZDA decreased ingeneral under irradiation of 365 nm UV light, but the changes of synthesized LAPE andHBAPE were on the increase. The results further proved that intermolecular hydrogen bondcould stable the cis structures of LAPE and HBAPE. With the increase of the stability of cisisomers, the rigidity enhanced, the fluorescence intensity and fluorescence quantum yieldsincreased accordingly.