Preparation And Applications Of Lignin-Based Azo Polymer Colloidal Spheres

Preparing nano materials from novel azo polymers by self-assembly technology, investigating self-assembly mechanisms and further exploring their applications have theoretical value and practical significance. In this work, based on the successfully synthesis and characterization of lignin-based azo polymers, their photo-responsive behaviors were studied. Furthermore, self-assembly of the polymer AL-azo-COOEt in mixed solvents, the applications of self-assembled colloidal spheres from AL-azo-COOEt were also investigated. The main results are shown as follows:The photo-responsive behaviors of lignin-based azo polymers and other synthesized azo polymers were studied. The difference of the substituent groups(-COOEt,-NO2 and-OCH3) in electronegativity(-NO2 and-COOEt have negative conjugation and induction effects, while-OCH3 has positive induction effect), lead to the photo-responsive behaviors of AL-azo-COOEt, AL-azo-NO2 were obvious while that of AL-azo-OCH3 was almost none. Furthermore, there was a significant difference between lignin-based azo polymers and other synthesized azo polymers with the same substituent groups. It was speculated that the strong resistance of lignin backbone prevent the azobenzene groups from tran-cis isomerizing. The photo-responsive behavior of AL-azo-COOEt was weaker than PEAPB6P-AA which contains the same substituent groups-COOEt. Photo-responsive behavior of PNAPE was too fast to observe while AL-azo-NO2 had significant photo-responsive behavior. The steric resistance in AL-azo-NO2 slowed down the isomerization process and the photo-responsive behavior could be observed. PEAPE which contained the same substituent groups-OCH3 had obvious photo-responsive behavior while AL-azo-OCH3 could not observe the photo-responsive behavior.The self-assembly behavior of AL-azo-COOEt in mixed solutions(THF/H2O) and self-assembled colloids were studied by dynamic light scattering(DLS), static light scattering(SLS), transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The results showed that AL-azo-COOEt could self-assemble into colloidal spheres and the colloidal spheres had relatively hydrophobic interior and hydrophilic exterior, and the azobenzene groups mainly distributed in the interior. Van der Waals force and π-π effect promoted the self-assembly process. The initial concentration of polymer and water adding speed influenced the mean particle size and particle size distribution. The more the initial concentration was, the bigger the mean particle size was and the narrower the particle size distribution was. The faster the water adding speed was, the smaller the mean particle size was and the wider the particle size distribution was.The two-dimensional arrays of AL-azo-COOEt colloidal spheres were prepared via vertical deposition and the suitable preparation conditions were formed. The entrapment and controlled release behavior of AL-azo-COOEt colloidal spheres were also studied with hydrophobic drugs doxorubicin(DOX) and avermectin(AVM) as probes. The results showed that AL-azo-COOEt colloidal spheres could entrap DOX and AVM effectively and the drugs could release slowly in the p H buffer solution(p H 8~10) and methanol/H2 O mixed solution respectively.