Functional Side-Chain Azobenzene Copolymer And Star Shaped Polymer: Controlled/"Living" Radical Polymerization Synthesis And Investation On Their Properties

In this thesis, linear and two miktoarm star side-chain liquid crystalline (LC) block copolymers with p-methoxyazobenzene moieties were prepared by a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) techniques. Additionally, differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM) were used to investigate LC properties of the linear and the miktoarm star block copolymers. On the other hand, the amphiphilic azobenzene copolymer (PSAzo-b-NIPAAM) was successfully synthesized by the reversible addition fragmentation chain transfer (RAFT) technique and the self-assembly and fluorescent properties of the amphiphilic azobenzene copolymer were also investigated.The main work in this thesis is summarized as following:(1) One linear and two miktoarm star side-chain liquid crystalline (LC) block copolymers with p-methoxyazobenzene moieties were prepared by a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) techniques. Firstly, ROPs ofε-caprolactone (ε-CL) were carried out catalyzed by Sn(Oct)2 using three multifunctional initiators, hydroxyethyl 2-bromoisobutyrate (AB type), 3-hydroxy-2-(hydroxymethyl)-2-methylpropyl 2-bromo-2-methylpropanoate (A2B type) and 2,2-bis(hydroxymethyl)propane-1,3-diyl bis(2-bromo-2-methylpropanoate) (A2B2 type), at 110 oC in toluene, respectively. Secondly, the previously obtained poly(ε-caprolactone)s (PCLs) with bromines functionalities were used as the macroinitiators to conduct ATRP of 6-(4-methoxy-4-oxy-azobenzene) hexyl methacrylate (MMAZO) with CuBr/PMDETA as the catalyst systems at 85 oC in anisole to prepare the linear and miktoarm side-chain LC block copolymers (PCL-b-PMMAZO, (PCL)2-(PMMAZO) and (PCL)2-(PMMAZO)2). The produced polymers were well-controlled with the controlled molecular weights and the relatively narrow molecular weight distributions (Mw/Mn≤1.35). The structures of the obtained polymers were all characterized by 1H NMR, FT-IR and GPC analysis. Furthermore, the LC properties of the linear and miktoarm star block copolymers were also investigated by differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM).The structures of the polymers and the molecular weights of the azo polymer chains had obvious effect on the thermal and the LC properties.(2) The well-defined azobenzene-containing homopolymers, poly{1-(4-(4-vinylbenzyloxy)phenyl)-2-(4-methoxyphenyl)diazene}(PSAzo), was synthesized via RAFT polymerization of StAzo in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2'-azobisisobutyronitrile (AIBN) as the initiator. Then, the well-defined azobenzene-containing homopolymers was used as the macro-RAFT agent to conduct polymerization of NIPAAM in THF at 75 oC. The polymers obtained were well-controlled with the controlled molecular weights and the relatively narrow molecular weight distributions (Mw/Mn≤1.6). All the polymers were characterized by the 1H NMR, GPC and FT-IR spectra. The self-assembly behavior of the amphiphilic copolymers in water was studied by the transmission electronic microscopy (TEM) with different UV irradiation time. The amphiphilic copolymer (PSAzo-b-PNIPAAM3, (Mn(GPC) = 10770 g/mol, Mw/Mn = 1.42) can formed nanosized spherical micelles. Most interesting, the size of the spherical micelles increased with the UV irradiation time. However, no obvious fluorescent emission was observed.