Covalent functionalization and noncovalent carbon nanotubes

O trabalho desenvolvido nesta dissertaÃÃo consiste no estudo do processo de funcionalizaÃÃo nÃo covalente de nanotubos de carbono com copolÃmeros tribloco e dibloco e a funcionalizaÃÃo covalente de nanotubos de carbono com Ãcido esteÃrico. A funcionalizaÃÃo nÃo covalente dos nanotubos de carbono foi realizada utilizando copolÃmeros tribloco e dibloco [tribloco E69S15E69, E69S7E69 (E = Ãxido de etileno, S = Ãxido de estireno), E65G7E65(E = Ãxido de etileno, G = Ãxido de fenilglicidil), o copolÃmero dibloco E20CL10 (E = Ãxido de etileno, CL = Ɛ-caprolactona)]. A individualizaÃÃo dos nanotubos de carbono com os copolÃmeros (em soluÃÃo) foi realizada usando a tÃcnica de agitaÃÃo, sonicaÃÃo e centrifugaÃÃo. As amostras obtidas foram caracterizadas por espectroscopia Raman ressonante excitando com laser de comprimento de onda de 532 nm (2,33 eV), e por fotoluminescÃncia no intervalo de 800 â 1700 nm. As caracterizaÃÃes foram realizadas de forma a identificar os tipos de nanotubos semicondutores, por fotoluminescÃncia, assim como tambÃm os demais por espectroscopia Raman. As caracterÃsticas espectrais comprovam a individualizaÃÃo dos nanotubos de carbono utilizando os copolÃmeros como meio dispersivo. A funcionalizaÃÃo covalente dos nanotubos de carbono foi realizada empregando Ãcido esteÃrico, e desenvolvida em 3 etapas: i) carboxilaÃÃo dos nanotubos de carbono utilizando a mistura H2SO4:HNO3; ii) funcionalizaÃÃo dos nanotubos com grupos COCl e iii) funcionalizaÃÃo dos nanotubos de carbono com Ãcido esteÃrico. A caracterizaÃÃo da amostra obtida foi realizada usando espectroscopia Raman ressonante, com excitaÃÃo no comprimento de onda de 514,5 nm (2,41 eV), FTIR, DSC em atmosfera de N2 e taxa de aquecimento de 10 ÂC/min no intervalo de 25 a 400 ÂC, e TGA em atmosfera de N2 e taxa de aquecimento de 10ÂC/min no intervalo de 25 a 900 ÂC. Estas caracterizaÃÃes foram realizadas de modo a obter elementos que indiquem a funcionalizaÃÃo covalente dos nanotubos de carbono com o Ãcido esteÃrico. Essa funcionalizaÃÃo reflete mudanÃaas na estrutura cristalina dos nanotubos de carbono, observada na espectroscopia Raman ressonante e bandas correspondentes a ligaÃÃes -OOC-O-COO- tÃpica de anidrido nos espectros de FTIR, assim como mudanÃas no comportamento tÃrmico dos nanotubos funcionalizados em relaÃÃo aos nanotubos de carbono puro.The work developed in this thesis consists in the study of the process of non covalent functionalization of carbon nanotubes with triblock and diblock copolymers and covalent functionalization of carbon nanotubes with stearic acid. The non covalent functionalization of carbon nanotubes were realized using triblock copolymer [triblock E69S15E69, E69S7E69 (E= ethylene oxide, S = styrene oxide), E65G7E65 (E = ethylene oxide, G = phenyl glycidyl ether), the diblock copolymer E20CL10 (E = ethylene oxide, CL = Ɛ-caprolactone)] e SDS (sodium dodecyl sulfate). The individualization of carbon nanotubes with copolymer and SDS, were performed by stirring, sonication and centrifugation. The resulting samples were characterized using the Raman resonant spectroscopy study, exciting in wavelength of 532 nm (2.33 eV). The photoluminescence studies, in the copolymers and SDS solution, were realized using a detector InGaAs for detecting light in the intermission of 800 â 1700 nm, and a lamp of Xe, exciting in spectral intermission of 500 â 850 nm. The characterizations were used to identify the type of semiconductors carbon nanotubes, by photoluminescence, as well as the other identified by resonant Raman spectroscopy and the aspects that showing the individualization of carbon nanotubes using copolymers matrix. The covalent functionalization of carbon nanotubes were realized using stearic acid. The functionalization was performed in three steps, carboxylation of carbon nanotubes, usingfor this the mixture H2SO4:HNO3, functionalization of carbon nanotubes with COCl groups and functionalization of carbon nanotubes with stearic acid. The characterization of the obtained sample was realized using the Raman resonant spectroscopy study, exciting with laser at wavelength of 514,5 nm (2,41 eV), FTIR, DSC, in N2 atmosphere and heating rate of 10ÂC/min in the intermission of 25 â 400 ÂC, and TGA, in N2 atmosphere and heating rate of 10 ÂC/min with intermission 25 â 900 ÂC. These characterizations were realized in order to confirm the covalent functionalization of the carbon nanotubes with stearic acid, obtaining shift in the crystalline structure of the carbon nanotubes, showed by the Raman resonant spectroscopy study and corresponding -OOC-O-COO- anhydride bond also showed in the FTIR spectroscopy, as well as change in the thermal behavior of the carbon nanotubes functionalized in comparison with pure carbon nanotubes