Study On The Interactions Between Polylluorenes Containing Benzophenone Croup And Single-Walled Carbon Nanotubes And Their Applications

Semiconducting single-walled carbon nanotubes(s-SWCNTs)can be used as channel materials for high-performance field-effect transistors(FET)due to their unique electrical properties,which can be applied for flexible electronics.However,commercial single-walled carbon nanotubes(SWCNTs)are a mixture of two types of carbon nanotubes with different electrical properties,which can be divided into s-SWCNTs and metallic nanotubes(m-SWCNTs).Therefore,enrichment of high-purity s-SWCNTs from SWCNTs mixture is rather important.Among the reported methods,conjugated polymer-wrapping method has attracted researchers'attention due to the simple process and high purification efficiency.Since the first report,conjugated polymers with various structures,typical polyfluorenes,have been designed and synthesized for sorting of s-SWCNTs with specific chirality or diameter.By rationally designing the backbones and side chains,changing the sorting conditions such as solvent,sonication temperature,centrifugation time and speed,researchers have investigated the interactions between conjugated polymers and SWCNTs In recent years,various functional conjugated polymers were synthesized to sort of s-SWCNTs and functional complexes were thus achieved.After purification,functional polymers were utilized to:(1)deposit s-SWCNTs on the specific areas of substrates or(2)make polymers detach from the surface of nanotubes to achieve polymer-free s-SWCNTs.Benzophenone has unique photo-reactive properties.Under the UV irradiation,keto carbonyl would be easily broken and generates double radicals,one of which would a hydrogen atom from the surrounding environment,another would recombine to form a stable C-C bond.The photoreaction has been widely applied in photoimmobilization and photografting areas.In this thesis,a fluorene-based copolymer containing benzophenone in the side chain and polyfluorenes containing benzophenone in the backbone were constructed.The interactions between the polymers and SWCNTs were explored and then the photosensitivity of benzophenone was utilized to conduct preliminary researches on the further applications of polymer-wrapped s-SWCNTs.The detailed research contents are as following(1)A functional monomer containing benzophenone was synthesized,and a fluorene-based alternative copolymer PFBP containing benzophenone group in the side chain was prepared by a Suzuki coupling reaction.Based on the ultraviolet-visible(UV-vis)absorption spectroscopy characterization,it was found that the conjugated system size of PFBP and poly(9,9-dioctylfluorene)(PFO)with similar molecular weights were also the same.The interactions between PFBP and SWCNTs were investigated and the results showed that at the PFBP:SWCNTs ratio of 5:1,PFBP has the ability to sort of high-purity s-SWCNTs with higher yield than PFO in toluene.It should be noted that PFBP has the tendency to sort of(9,7)s-SWCNTs with higher diameter.Photosensitivity of benzophenone in PFBP was utilized to immobilize s-SWCNTs on the flexible polyethylene terephthalate(PET)substrate successfully.By using photomasks,s-SWCNT patterns containing circle arrays with size from 60 ?m to 1000 ?m were fabricated and a more complex circuit pattern was also prepared(2)Benzophenone was introduced to the backbone of polymers,and an alternative copolymer PFB consisting of benzophenone and 9,9-dioctylfluorene,and random copolymers containing benzophenone and 9,9-dioctylfluorene with different ratios(BP)5n(FO)16n,(BP)6n(FO)16n,(BP)8n(FO)16n,(BP),2n(FO)16n and(BP)16n(FO)16n were synthesized by a Suzuki coupling reaction.PFO was used for reference.The interactions between PFB and SWCNTs were investigated,and factors such as solvent,PFB:SWCNTs ratio,and molecular weight were investigated.It was found that PFB has no selectivity for s-SWCNTs under conditions in this thesis.For random copolymers(BP)x(FO)y,it was found that at the polymer:SWCNTs ratio of 3:1 and 5:1,(BP)5n(FO)16n and(BP)6n(FO)16n showed good selectivity for s-SWCNTs.With the content of benzophenone increasing,the selectivity of polymers decreased.In addition,to achieve pure s-SWCNTs,photosensitivity of polymers was utilized to destroy the conjugated system of polymers and the interactions between polymers and nanotubes decreased,leading to partial polymer removal from nanotube surface.It was calculated by UV-vis absorption spectra that the desorption efficiency of(BP)5n(FO)16n is about 34%,(BP)6n(FO)16n 43%and(BP)8n(FO)16n 57%,respectively.