Study On Synthesis Of Amphiphilic Block Copolymers And Self-assembly In An Ionic Liquid [BMIM][PF₆]

Molecular design, synthesis and properties of block copolymers with well-defined structure have been subjects of numerous studies, the block copolymers with well-defined were synthesis via many method, such as anionic polymeriation and controlled/living free radical polymerization et al. In the last decade, the development of anionic polymeriation and living/controlled free radical polymerization has provided control over molecular architectures for a variety of monomers, allowing the easy synthesis of block copolymers with well-defined molecular weights and narrow molecular weight distributions. The techniques mainly include Initiator-transferagent-terminator (Iniferter), Nitroxide Mediated Polymerization (NMP), atom-transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer polymerization (RAFT). RAFT polymerization is probably the most versatile tool of the prominent living/controlled free radical polymerization techniques to synthesize polymers with complex architecture ranging from block to star, as it is tolerant of a wide range of functionality in the monomer and solvent.The main works and results in this paper are described as follows:1) Synthesis of AB-Diblock copolymers by ATRP and Its Self-assembly in an ionic liquid [BMIM][PF₆]The block copolymer of poly(styrene)-block-poly-(acrylic acid) has been synthesized by atom transfer radical polymerization (ATRP) method. Three amphiphilic copolymers with different molecular weight form micelles in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]). The self-assembled morphologies of the copolymers are strongly dependent on the length of PAA block chains when the chain length of PSt is fixed. With the increase of molecular weight of PAA in diblock copolymers, some spherical micelles are obtained. With further decrease of PAA molecular weight in copolymers, the spherical morphology is turned to peanut.2) Synthesis of PSt-PAA-PSt block copolymers and its self-assembly in ionic liquid [BMIM][PF₆]The Block copolymer Polystyrene-b-Poly(acrylic acid)-b-Polystyrene (PSt-b-PAA-b-PSt) was synthesized via Reversible Addition-Fragmentation Chain Transfer polymerization. Three block copolymers with different molecular weight were self-assembly by co-solvent method in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]). The self-assembled morphologies of the copolymers are strongly dependent on the length of PAA block chains when the chain length of PSt is fixed. With the decrease of molecular weight of PAA in block copolymers, the resulting aggregate are spheres. With further decrease of PAA molecular weight in copolymers, the sphere morphology is turned to core-shell spheres micell. Micellar morphologies is temperature-independent between 25 and 100℃3) Synthesis of PCL-PEG-PCL block copolymers and its self-assembly in ionic liquid [BMIM][PF₆]Four kinds of PCL-PEG-PCL copolymers were successfully prepared through changes in the feed ratio of CL to PEG by anionic ring-opening polymeriation. The nanostructures of the PCL-PEG-PCL micelles formed in ionic liquid were observed by TEM (transmission electron microscopy) and DLS (dynamic light scattering). The self-assembled morphologies of the copolymers are strongly dependent on the length of PCL block chains when the chain length of PEG is fixed. With the decrease of molecular weight of PCL in block copolymers, the predominant micellar morphologies are spheres and core-shell. With further increase of PCL molecular weight in copolymers, the morphology is turned to willow leaf and wormlike. Micellar morphologies is temperature-independent between 25 and 100℃.4) Synthesis of PLA-PEG-PLA block copolymers and its self-assembly in ionic liquid [BMIM][PF₆]The triblock copolymer polylactide-poly (ethylene glycol)-polylactide, PLA-PEG-PLA were synthesized. Four block copolymers with different molecular weight were self-assembly in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]). The self-assembled morphologies of the copolymers are strongly dependent on the length of PLA block chains when the chain length of PEG is fixed. With the decrease of molecular weight of PLA in block copolymers, the predominant micellar morphologies are spheres and core-shell. With further increase of PLA molecular weight in copolymers, the morphology is turned to willow vesicles and wormlike. Micellar morphologies is temperature-independent between 25 and 100℃.5) Synthesis of PSt-PEG-PSt block copolymers and its self-assembly in ionic liquid [BMIM][PF₆]Amphiphilic triblock copolymers with different molecular weight and low polydisperities was synthesized by atom transfer radical polymerization (ATRP). Four amphiphilic copolymers with different molecular weight form micelles in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]). The self-assembled morphologies of the copolymers are strongly dependent on the length of PSt block chains when the chain length of PEG is fixed. With the decrease of molecular weight of PSt in block copolymers, the predominant micellar morphologies are spheres and some vesicle. With further increase of PLA molecular weight in copolymers, the morphology is turned to fusiform and peanut. Micellar morphologies is temperature-independent between 25 and 100℃.