Synthesis Of Azo Side-Chain Polymer Via Living Radical Polymerization And Photoinduced Behaviors

In this thesis, we prepared three-arm star azo side-chain liquid crystalline (LC)homopolymers and block copolymers by atom transfer radical polymerization (ATRP)method. And we also synthesized linear azo homopolymers and block copolymers viareversible addition-fragmentation chain transfer (RAFT) polymerization method. Theobtained homopolymers films were used to inscribe surface relief gratings (SRGs). Theresults were shown as below.The ATRPs of 6-(4-methoxy-4'-oxy-azobenzene) hexyl methacrylate (MMAZO)were carried out using 1,3,5-(2'-bromo-2'-methylpropionato)benzene (BMPB) as initiator,CuBr as the catalyst and HMTETA as the ligand in anisole solution. The polymerization ofMMAZO proceeded in a controlled/'living' way. The glass-transition temperature and LCphase-transition temperature increased with the increase of molecular weight ofhomopolymer. The three-arm star azo block copolymers can also be obtained using PMMAas macro-initiator via ATRP. The phase transition temperature of the block copolymerswith the same PMMA block was similar to that of homopolymer. However, theglass-transition temperature of the copolymer decreased at low azo content and thenincreased with the increasing molecular weight. The UV-vis absorbance intensities of theazo polymers decreased with decreasing of azo contents. With illumination of linearlypolarized Kr~+ laser beam, the surface relief gratings with 2.3% diffraction efficiencyformed on homopolymer films were observed, and the molecular weights of PMMAZOhad less influence on the inscribed SRGsThe well-defined photoresponsive polymethacrylate containing azo chromophore,poly {1'-octyloxy-4'-(6-methacryloxy)hexyloxy-5'-phenylmethaneone-(2-phenyl) azobenzene (AHMA)} (PAHMA), was prepared via RAFT polymerization in anisolesolution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and2,2'-azobisisobutyronitrile (AIBN) as an initiator. The polymerization of AHMAproceeded in a controlled/'living' way. Block copolymers can also be obtained usingPAHMA as macro-RAFT agent, these results indicated that most of the PAHMA chainswere still 'living'. On irradiation with a linearly polarized Kr~+ laser beam, the birefringencewas induced in the polymer film to the level of 0.075. With illumination of linearlypolarized Kr~+ laser beam at modest intensities, significant SRGs with 1% diffractionefficiency formed on the polymer films were observed.