Application Of Living Radical Polymerization In Synthesis Of Cyclic Polymers And Emulsion Polymerization Induced Self-assembly

Since living radical polymerization was developed, various topological polymers including macrocycle-based polymers were successfully synthesized and studied. Due to the distinct properties of cyclic polymers, a lot of concerns were attracted. In this dissertation, a series of macrocycle-based polymers with complex topologies were synthesized, and their structure and properties were characterized. Moreover, living radical polymerization lead directly to the development of polymerization induced self-assembly, here we achieved the polymerization induced self-assembly process in water by the combination of RAFT polymerization and Emulsion polymerization. The primary results acquired are listed as follows:1. Graft copolymers with pendant macrocycles were synthesized via "graft onto" method. First, cyclic polystyrene (PS) was achieved by the combination of atom transfer radical polymerization (ATRP) and Cu-catalyzed azide-alkyne cycloaddition (CuAAc), and then an alkynyl group was introduced to cyclic PS. Meanwhile, poly(3-azide-2-hydroxypropyl methacrylate) (PGMA-N3) was synthesized by ATRP of glycidyl methacrylate (GMA) and successive ring-opening of pendant epoxide ring with NaN3. Graft copolymers were achieved by the following click reaction between PGMA-N3 and alkynyl-containing cyclic PS. GPC and 1H NMR were utilized to characterize the obtained graft copolymers, and a maximal grafting density of 20% was observed. Thermal behaviors of linear PS, cyclic PS and PGMA grafted with cyclic PS (PGMA-g-cPS) were investigated by differential scanning calorimeter (DSC), and Tg of PGMA-g-cPS is higher than those of linear and cyclic PS.2. Cyclic PEO-PS copolymer with two pendent coumarin groups was prepared by the combination of atom transfer radical polymerization (ATRP) and "click" chemistry. Coumarin group and an ATRP initiator were first introduced to each end of PEO chain, and following ATRP of St afforded us block polymer PS-PEO-PS. The cyclization was achieved by bimolecular coupling. When cyclic polymer with two coumarin groups was irradiated under UV light at λ= 365 nm, multicyclic polymer was achieved due to the dimerization of pendant coumarin group. Subsequently, multicyclic polymer can be divided into single macrocycle under UV irradiation at λ= 254 nm via the photocleavage of coumarin dimer.3. A series of dendritic ATRP initiators were first prepared by catalyst-free click reaction, and in these initiators, the amounts of alkynyl groups and bromine groups are strictly equal. Then the initiators were used in the ATRP of styrene to afford multi-arm star polystyreness (PS). After azidation of multi-arm star PS, flower-shaped polymers were achieved by intramolecular cyclization via CuAAc. Flower-shaped polymers with three and six petals are presented in this work. Due to the triazole groups of dendritic initiators, fluorescence emissions were observed. Star polymers exhibited high fluorescence intensities than those of initiators. Moreover, flower-shaped polymers showed us high fluorescence intensities than those of star polymer precursors due to the cyclic topology.4. A RAFT agent PEO-CPDB was used in the polymerization of 4VP and a macromolecular surfactant with short P4VP chain was produced. Then both PEO-CPDB and obtained surfactant were used together in emulsion polymerization of 4VP. Nanoparticles with nonspherical morphologies were obtained in this process. Moreover, when a highly hydrophilic initiator ACVA-Na+ and a small amount of HPMA as the comonomer were used in emulsion polymerization of 4VP, nano fibers and micron fibers were achieved.