Preparation Of Fluorinated Block Copolymer Nanomaterials By RAFT Polymerization-Induced Self-Assembly

Block copolymer is a special polymer prepared by connecting two or more polymer segments with different properties.It has broad application prospects in chemical,pharmaceutical,construction and other fields.Block copolymers with controllable chemical structure can be synthesized by RAFT PISA technology.Block copolymers with controllable morphology can also be prepared by in-situ self-assembly.Fluoropolymers have a series of advantages such as excellent chemical stability,weather resistance and low surface energy.Introducing fluorinated block into block copolymers can greatly improve the properties of block copolymers.scCO₂ is a green,cheap and chemically stable solvent with good solubility for most fluorinated polymers.In this paper,fluorinated block copolymer nanomaterials with different structures were synthesized by RAFT-PISA in the medium of scCO₂.The research contents of this paper include the following parts:In the first part,fluorinated diblock copolymer nanomaterials were synthesized by RAFT PISA in scCO₂ medium.First,DDMAT was synthesized.Then,Preparation of PDFMA-DDMAT with DDMAT as chain transfer agent.Finally,PDFMA-DDMAT was used as the macro-CTA to prepare the fluorinated block copolymer nanoparticles by RAFT PISA in scCO₂.The products were characterized by FT-IR,¹H NMR and GPC.The effects of temperature,pressure and block length on the morphology of fluorinated diblock copolymer nanomaterials were also investigated.The results showed that fluorinated diblock copolymer nanospheres with good morphology could be obtained when the reaction temperature was67?the pressure was 30 MPa and the degree of polymerization of PMMA was about 500.In the second part,the effects of different CTAs on the morphology of fluorinated diblock copolymer nanomaterials prepared in scCO₂ were studied.A series of fluorinated diblock copolymer nanomaterials were synthesized by RAFT PISA using four small molecular CTAs with different activating groups?R group?and leaving groups?Z group?.It was found that the use of CTAs with higher chain transfer constants was beneficial to the preparation of fluorinated diblock copolymer microspheres nanomaterials with better morphology.The effects of different small molecular CTAs and concentrations on the morphology of fluorinated diblock copolymer nanomaterials by RAFT PISA were also studied.The results show that fluorinated nanomaterials with good morphology can be obtained by synergistic action of small molecular CTA and macro-CTA.In the third part,the main content is to synthesize fluorinated triblock copolymer nanomaterials containing mPEG segments by RAFT PISA in scCO₂.First,mPEG-DDMAT was prepared.Then mPEG-b-PDFMA-DDMAT was prepared by RAFT polymerization.Finally,fluorinated triblock copolymer nanospheres was prepared by RAFT PISA in scCO₂.The effects of pressure,PMMA and mPEG block length on the fluorinated triblock copolymer nanomaterials were investigated.The results show that the morphology of the triblock copolymer microspheres is the best when the pressure is 30 MPa,the degree of polymerization of PMMA is about 500 and the molecular weight of mPEG is 2000 g/mol.Also,it was found that the size of fluorine-containing triblock copolymer nanospheres prepared by introducing mPEG₂₀₀₀ was 6-10 times larger than that of fluorinated diblock copolymer nanospheres.The fourth part is the synthesis and application of fluorinated triblock copolymer nanomaterials with different structures.Macro-CTAs with different block positions of mPEG were prepared by using different structure CTAs?Z-type and R-type?.Fluorinated triblock copolymer nanomicrospheres with different block structure sequences were prepared by RAFT PISA technology in scCO₂.The effects of molecular structure of macro-CTA and location of mPEG segment on the morphology of nanospheres were investigated.The results showed that the microspheres prepared by R-type CTA could be dispersed stably in water because the mPEG segment was located on the surface of the microspheres.The mPEG segment of the microspheres prepared by Z-type CTA was located in the inside of the microspheres and could not be dispersed stably in water.At the same time,it was found that the self-assembled trithioester groups of Z-type block copolymer microspheres were located on the surface of the microspheres,which was more conducive to loading Ag nanoparticles onto the surface of the microspheres by in-situ reduction.