Synthesis Of Amphiphilic Fluorinated Copolymers And Impacts Of Ionic Concentration On Self-assemble Behavior

RAFT polymerization technique is achieved through the reversible addition-fragmentation chain transfer mechanism and RAFT agent is the key for this mechanism. Therfore, RAFT agent's structure will directly affect the controllability and stability of polymerization as well as the microscopic chain composition of products. In this thesis, a series of amphiphilic RAFT agents were synthesized and used to control the emulsion polymerization of acrylic acid (AA) and2,2,2-trifluoroethyl methacrylate (TFEMA). The microstructure differences between synthesized copolymers were compared and influences of ionic strength on self-assembly behaviors of copolymers were studied. Moreover, RAFT polymerization of dimethylaminoethyl methacrylate (DMAEMA) and TFEMA was preliminarily investigated.A series of amphiphilic RAFT agents with different numbers of AA unit were prepared and their critical micelle concentration (CMC) in aqueous soluiton was determined by surface tension measurement. Then, the surfactant-free emulsion copolymerization of AA and TFEMA was carried out under the control of different amphiphilic RAFT agents. The kinetic study revealed that the controllability of the polymerization was improved and the polymerization rate increased with increasing AA unit's number in the amphiphilic RAFT agent. Dynamic light scattering (DLS) was used to trace the particle size and size distribution during polymerization progress. Particle number in copolymerization system was calculated to reveal nucleation mechanism, which indicated the hydrophilicity of amphiphilic RAFT agent also affect the nucleation mechanism. Gel permeation chromatography (GPC) results showed that the molecular weight distribution was narrow, reflecting a good controllability of copolymerization. The chemical structure of the copolymer was characterized by nuclear magnetic resonance (NMR), suggesting the gradient profile of the copolymer.Impacts of ionic strength on CMC values as well as self-assembly of the copolymer were studied in detail. CMC values of copolymers significantly decreased with increasing the salt concentration. Shapes and size of the micelles were investigated by transmission electron microscopy (TEM) and DLS. The sample coded as S-1could self-assemble to form rod-like micelles in dioxane-water mixture and tended to form spherical micelles with the increase in ionic strength. However, the shape of micelles formed by S-2changed from spherical to rod-like with the increasing in ionic strength. For micelles formed by S-1, particle sizes decreased with increasing ionic concentration, while particle sizes of micelles formed by S-2increased.In addition, DMAEMA-b-TFEMA block copolymer was obtained through RAFT polymerization. The polymerization kinetics was in good accord with the feature of control radical polymerization. The low critical solution temperature (LCST) of the block copolymer was measured by UV-Vis spectrophotometer, which was around48℃.Amphiphilic RAFT agent was used to control miniemulsion polymerization and surfactant-free emulsion polymerization of DMAEMA and TFEMA.