Synthesis And Characteristic Of Coumarin-containing Polymers By RAFT Polymerization

In this thesis, the reversible addition fragmentation chain transfer (RAFT) polymerizations of coumarin-containing monomer were studied. The obtained polymers were characterized by various techniques. The following systems were details were showed as below:(1) RAFT polymerization of 7-(4-(Acryloyloxy)butoxy) coumarin(7AC) was carried out using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as RAFT agent and 2,2'-azobisisobutyronitrile (AIBN) as the initiator. The polymerization behavior was investigated. The obtained coumarin unit containing polymers were characterized with UV-vis and fluorescence spectra techniques. The post-crosslinking via the photodimerzation reaction between the coumarin units under irradiation of UV light source was investigated.(2) A brush-type amphiphilic diblock copolymer, (poly (poly (ethyleneglycol) methylethermethacrylate)–block–poly(7-(4-(acryloyloxy)butoxy)coumarin)) (P(PEGMA)-b-P(7AC)) were synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerizations. The diblock copolymers structures were characterized by gel permeation chromatography (GPC), and proton nuclear magnetic resonance (1H NMR) spectroscopy. The characteristic of the polymer was investigated.The results were shown as below:In the first system, the reactions presented as"living"/controlled radical polymerizations. The obtained P7AC with the well-designed structure showed strong fluorescence under the exciting with a 329 nm light. The fluorescence intensities of the polymers increased with the increasing molecular weight of P7AC while with same coumarin unit concentration. However, the molecular weights of the polymers had no apparent effect on the ultraviolet absorption intensities. The coumarin structure existed in P7AC underwent [2+2] cycloaddition reaction (photodimerization) under UV irradiation in tetrahydrofuran (THF) solution. The UV-vis absorption of P7AC (λmax = 322 nm) decreased after irradiation under UV light. The molecular weight and PDI of the polymer after irradiation was larger than those before irradiation.In the second system, the polymers with different ratio of hydrophobe/hydrophile unit were synthesized. At same coumarin unit concentration, a polymer with more chromophore units in the same chain showed stronger fluorescence intensities. The hydrophile units won't show significance effect on the polymer's fluorescence. The amphiphilic polymer shown excellent surface activity in water. The aqueous solution of this amphiphilic polymer showed abrupt decreasing in the value of surface tension within certain concentration range. TEM results of the micelles formed by the amphiphilic copolymer through self-assembling in water showed as spherical shape.