Synthesis And Properties Of Novel Side-chain Azobenzene Polymer

Azobenzene is a typical kind of optical-active functional groups, which can carry out reversible isomerization between the trans and cis isomers caused by light irradiation or thermal treatment, accompanied by physical and chemical changes in the molecular shape and dipole moment. When the azobenzene groups are bond to the polymer chain, the repeated isomerization may lead to a series of motions of the chromophores and the polymer chain. Azobenzene-containing polymers not only have the unique photo-responsive properties of the azobenzene chromophores but also the good stability and mechanical properties of polymer materials, in which, the side-chain azobenzene polymers have attracted much more attention because of the simple synthesis and the good designability of molecules. Thus, design and synthesis of novel side-chain azobenzene polymers and explore the effects of the different molecular structures and chemical components on their photo-induced isomerization property as well as the relationship between the liquid crystal property, the self-assembled nano-structures and photo-responsive properties, are of great importance to their potential application in optical materials, liquid crystal materials, controlled drug release, nano functional materials and so on.In this thesis, we designed and synthesized a series of side-chain azobenzene block copolymer/3-miktoarm star terpolymers, the main researches included the following three parts:(1) Coil-rod AB diblock copolymers PGMA-b-PAzoMA were synthesized via RAFT. The effects of the chemical structures and molecular weights on the thermotropic liquid crystal and optical response properties were studied using UV-vis analysis. To explore the relationship between the microphases, microdomains and photoisomerization, three kinds of polymer thin films were prepared, which are as-coated film, annealed film and cross-linked film.(2) Azobenzene side-chain polymer PAzoMA was firstly introduced into ABC 3-miktoarm star terpolymers as an arm. Epichlorohydrin was chosen as the "core", a combination of click chemistry and ATRP was used to prepare3-miktoarm star terpolymers (MPEG)(PS)(PAzoMA) with different PS or PAzoMA arms. The effects of the chemical structures and molecular weights on the thermotropic liquid crystal and photoinduced isomerization were studied in detailed. The influences of the star topology structure on microphase-separation and self-assembled behavior in selective solvent were also studied, it was found that the (MPEG)(PS)(PAzoMA) could self-assembled into three kinds of bowl-like aggregates in aqueous solution. The relationships of self-assembled nano-structures and the photo response properties were explored via UV-vis analysis. The honeycomb porous thin films of3-miktoarm star terpolymers were prepared using a static breath figure method and the influence of photoinduced orientation of azobenzene groups on the surface porous structure in honeycomb thin films were also investigated.(3)(MPEG)(PAzoMA)(PBLG)3-miktoarm star terpolymers with a rigid PBLG arm were synthesized via a similar route and the effects of the chemical structures and molecular weights on the thermotropic liquid crystal and photoinduced isomerization were studied. The influences of the star topology structure and the existence of rigid PBLG arm on the self-assembled behavior in selective solvent were also investigated, it was found that (MPEG)(PAzoMA)(PBLG) star terpolymers with shorter PAzoMA arm (DP=57) could form a novel self-assembled aggregates with sphere-containing fusiform shaped structures. The shape deformation of porous structures in honeycomb porous polymer thin films induced by linear polarized light was observed by SEM.