Preparation Of Azo Polymer Bearing Indazole Moiety Via RAFT Polymerization And Investigation On Their Properties

In this thesis, phenylazo indazole-terminated polystyrene (PS) is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Intense fluorescence from aggregates of PS were also investigated in chloroform solution. Additionally, linear azo polymers (LAP) and hyperbranched azo polymers (HAP) were successfully synthesized via RAFT polymerization of two novel azobenzene monomers (M1 and M2) in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2'-azobisisobutyronitrile (AIBN) as the initiator. Their optical properties in solution were investigated. Details were summarized as the following:(1). The well-defined phenylazo indazole-terminated polystyrene (PS) was successfully prepared via RAFT polymerization of styrene (St) mediated by a novel chain transfer agent (CTA) bearing phenylazo indazole moieties in the Z group, benzyl-4- dimethylaminophenylazo-5-indazole-1-carbodithioate (BPCD). The fluoresce ence- emission of BPCD and the phenylazo indazole-terminated PS in chloroform (CHCl3) before and after the 365 nm ultraviolet irradiation was investigated. Interestingly, the fluorescence intensities of BPCD and phenylazo indazole-terminated PS in CHCl3 were both sensitive to the 365 nm ultraviolet irradiation. The fluorescence intensities of these solutions increased with the irradiation time and reached maximum at 110 min. The light-driven fluorescence enhancements of BPCD and the phenylazo indazole-terminated PS were both attributed to the formation of aggregate originated from the trans-cis isomerization of azobenzene moieties in BPCD and PS chain, which was confirmed by transmission electron microscopy (TEM), 1H NMR, UV and dynamic light scattering (DLS) spectra.(2) The LAP and HAP were successfully synthesized via RAFT polymerization of two novel azobenzene monomers (4-methoxyl-4′-methacryloxyl azobenzene, M1 and 4-methacryl-4'-methacryloxyl-indazole-5-azobenzene, M2) in anisole solution using CPDN as the RAFT agent and AIBN as the initiator. The results showed that the polymerization of M1 could be well controlled. The kinetic plot was first order and the number-average molecular weight (Mn,GPC) of the polymer measured by GPC increased linearly with monomer conversion. However, during the copolymerization of M1 and M2 in HAP preparation, it didn't show living polymerization characteristic: the kinetic plot was not first order and the Mn,GPC increased nonlinearly with monomer conversion. However, successfully chain-extension reaction using HAP as a macro-RAFT agent and St as the second monomer showed that the HAP polymer chains were almost living. The optical behavior of LAP and HAP in chloroform solution under 365 nm UV irradiation were investigated.