Carbonyl Linker Hexafluoropropylene Oxide Oligomer-based Styrene Copolymerization

As a typical representative of fluorinated functional materials,fluorinated styrenic polymer not only has optical properties with high light transmittance and low refractive index,excellent hydrophobic and oleophobic surface properties,but also possesses low dielectric constant,high insulation electrical properties and the stability of corrosion resistance.Accordingly,it has been applied in the fields of national defense,medicine and economic construction,etc.However,few fluorinated styrenic monomers are commercially available,which limits the further research and application.It is believed that designing as well as synthesizing novel monomers with excellent performance and highly fluorinated,construction of a green,efficient and controllable copolymerization system of highly fluorinated styrene monomers are vital to the development of styrenic functional materials.Supercritical carbon dioxide(scCO2)has been increasingly accepted as the environmentally benign medium for its outstanding advantages,such as excellent solubility for fluorinated monomers/polymers and adjustable physical and chemical properties.Reversible addition-fragmentation transfer radical polymerization(RAFT polymerization)has a wide monomer adaptability,mild polymerization conditions,and good solubility of the reaction system.Therefore,it may be the most promising controllable/living free radical polymerization method in scCO2.It is believed that the structure of the target polymer may be effectively controlled via RAFT polymerization of fluorinated styrenic monomers in the scCO2,via which a series of fluorinated functional materials may be obtained to meet specific needs.Anionic polymerization may be the most controllable method among the living/controllable polymerization.Exploration of the anionic polymerization of the novel highly fluorinated styrenic monomer is of vital theoretical significance and application value to the design and precise control of the microstructure of fluorinated polymers,to the improvement/enhancement of performances of the polymer,and to the expansion the application of the polymeric materials.In our previous research,a series of hexafluorinated epoxy oligomer-based styrenes with carbonyl linkage(FEOnCOSt)have been designed and successfully synthesized based on the understanding of the intermolecular interactions in supercritical systems as well as the demand for the controllable preparation of fluorinated polymers.FEO3COSt is highly fluorinated,and has excellent homopolymerizability and broad application prospects.Based on the study on the controllable radical homopolymerization of FEO3COSt,the copolymerization performances of FEO3COSt will be further explored and evaluated,and an efficient and controllable copolymerization strategy of FEO3COSt will be constructed in the present thesis.It is expected that the present study may lay a solid foundation for the research and application of the novel FEO3COSt-based functional materials.Herein,the free radical copolymerization of FEO3COSt with four non-fluorinated monomers in scCO2,the controlled radical copolymerization of FEO3COSt with two monomers in scCO2(RAFT copolymerization),and the anion polymerization of FEO3COSt were systematically investigated.The main contents and results are as follows.(1)Study on the free radical random copolymerization of FEO3COSt in scCO2FEO3COSt was used as a model monomer,with which the free radical binary copolymerization of four non-fluorinated monomers,namely maleic anhydride(MAH),acrylonitrile(AN),methacrylate(MMA)and 1,3-butadiene(BD),was explored in scCO2.In addition,the ternary copolymerization of FEO3COSt,1,3-butadiene(BD)and p-divinylbenzene(DVB)was also studied.The copolymers were characterized and confirmed via1H NMR,FT-IR and MALDI-TOF.Followed by the morphology,hydrophobicity and thermal stability of the polymeric product were tested,and the performance of the free radical copolymerization of FEO3COSt was evaluated and verified.The copolymers were characterized and confirmed via 1H NMR,FT-IR and MALDI-TOF.Followed by the morphology,hydrophobicity and thermal stability of the polymeric product were tested,and the performance of the free radical copolymerization of FEO3COSt was evaluated and verified.By exploring the influence of comonomer types,monomer ratio,initiator dosage,reaction time on the free radical copolymerization of FEO3COSt,the reaction conditions were optimized,and a series of random copolymers were synthesized with a fluorinated content from 48%to 54%,and a molecular weight from 17,000 to 200,000.It is shown that among the four monomers of MAH,AN,MMA and BD,the copolymerization activity of FEO3COSt and BD is the best;in the ternary copolymerization,three-dimensional cross-linking polymer of a skeleton structure can be obtained when the DVB content was 20%.Moreover,with the increase of the fluorine content ing,the hydrophobicity of the copolymer increased,so did the thermal stability.(2)Exploration of controllable free radical copolymerization of FEO3COSt in scCO2The fluorinated RAFT agent pentafluorobenzyl dithiobenzoate(PFBDB)was prepared with good solubility and excellent performance in the free-radical polymerization of fluorinated monomers in scCO2.PFBDB was applied in the binary copolymerization of FEO3COSt with BD and isoprene(Ip)in scCO2.PFBDB and copolymers were characterized and identified via X-ray single crystal diffraction,1H NMR,FT-IR and MALDI-TOF techniques.The performances of controllable radical copolymerization of FEO3COSt were evaluated.By adjusting the mole ratio of FEO3COSt to BD,FEO3COSt to Ip,and the mole ratio of FEO3COSt to PFBDB,the controllable free radical copolymerization process and the influence of Mn were systematically explored.Moreover,the monomer conversion rate-polymer molecular weight polymerization curve was measured.Block copolymers of PFEO3COSt-b-PBD(Mn greater than 70,000),PFEO3COSt-b-PI(Mn greater than 120,000)and PFEO3COSt-b-PI-b-PFEO3COSt(Mn greater than 160,000)were successfully prepared in scCO2(3)Exploration of anionic polymerization of FEO3COStUsing n-butyl lithium as initiator and trifluorotoluene as the solvent,the anionic homopolymerization of FEO3COSt was explored,the hopolymer structure was characterized,the performance of FEO3COSt anionic polymerization was evaluated and verified.The reaction conditions of FEO3COSt were optimized by adjusting the reaction temperature,time and the amount of initiator.It was found that the optimal reaction temperature was 55? and the reaction time was 4 h.Under these conditions,when the mole ratio of FEO3COSt to n-butyl is 200:1,a homopolymer PFEO3COSt with a molecular weight of 143880 g/mol was obtained.