Amphiphilic Azobenzene Polymer And Triphenylamine-co-Bisindolyl Bi-functionalized Polymers: RAFT Synthesis And Investigation On Their Properties

In this thesis, azobenzene-containing polymers are synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and intense fluorescence from aggregates of azobenzene-containing amphiphilic diblock copolymers was also investigated. Additionally, the novel RAFT agent bearing with triphenylamine and bis(indolyl)methane groups was successfully synthesized and used as the RAFT agent for RAFT polymerization of styrene in anisole solution under thermal-initiation. Well-defined triphenylamine and bis(indolyl)methane center-functionalized polymer was obtained and characterized.The work in this thesis can be summarized as the following:(1) The well-defined azobenzene-containing homopolymers, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via RAFT polymerization of AHMA in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2'-azobisisobutyronitrile (AIBN) as the initiator. The first-order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs≤1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6-(4-phenylazophenoxy)hexyl methacrylate}-b-poly{2-(dimethylamino)ethyl methacrylate} (PAHMA-b-PDMAEMA), was prepared with obtained PAHMA as the macro-RAFT agent and DMAEMA as the second monomer. The structures and properties of the polymers were characterized by 1H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl₃) solution (PAHMA₂₃-b-PDMAEMA₉₇ (4×10^-5 M, Mn(GPC) = 18400 g/mol, PDI = 1.48) and PAHMA₂₈-b-PDMAEMA₁₁₇ (6×10^-5 M, Mn(GPC) = 19300 g/mol, PDI = 1.51)) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA-b-PDMAEMA in CHCl3 was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min then later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self-assembled micelles composed of azobenzene-containing amphiphilic diblock copolymers, (PAHMA-b-QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N-dimethyl formamide (DMF)/H2O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water.(2) A novel bis-functional RAFT agent bearing with triphenylamine (TPA) and bis(indolyl)methane (BIM) groups, {4-[bis(1-carbodithioic acid benzyl ester-indol-3-yl)methyl]phenyl}diphenylamine (BCIMPDPA), was synthesized and successfully used as the RAFT agent to mediate the polymerization of styrene (St). The polymerization results showed that RAFT polymerization of St 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, simultaneously, the polydispersity index value of the polymer was also relatively narrow. In addition, the existence of the TPA and BIM groups in the middle of polymer chain was confirmed by chain extension reaction and 1H NMR spectrum. The fluorescent intensity of the functionalized polystyrene (PS) was stronger than that of BCIMPDPA in chloroform solution at the same chromophore concentration. Similarly, the center-functioned PS (M_n(GPC) = 6200 g/mol, M_w/M_n = 1.37) also exhibited chemical reversible oxidation and reduction peaks of E_OX = -0.68 V, E_RE = -1.25V (vs. Pt).