Preparation Of Macroporous Polymers Stabilized By Graphene Oxide

Porous polymers consist of closed or open cells. This feature makes these materials interesting for a wide range of applications, such as sound and heat insulators, supports for catalysts and tissue growth, waste absorption, liquid chromatography and sensors. A strategy that is increasingly employed to prepare highly porous and well defined macroporous polymers is high internal phase emulsion (HIPE) template, whereby the droplets are used to create pores in a solid material by polymerization of the emulsion continuous phase. However, conventional HIPEs are usually stabilized by large amounts of expensive surfactant, which may bring difficulties in post processing and cause environmental pollution. Recently, particle-stabilized HIPEs, also known as Pickering HIPEs, have been used as templates to prepare cellular polymers termed poly-Pickering HIPEs. Thus far, Pickering HIPEs have been successfully stabilized by using various solid particles such as polymer microspheres, silica, titania, iron oxide and carbon nanotubes. Graphene oxide (GO), an important precursor of graphene, can be used as a Pickering stabilizer because of its amphiphilicity. In this regard, we prepared macroporous GO-polymer composites via water-in-oil (W/O) HIPE templates. The main contents of this dissertation are as follows:(1) The surface nature of GO flakes can tuned to be hydrophobic by taking advantage of the electrostatic attraction between cationic surfactant cetyl trimethyl ammonium bromide (CTAB) and GO flakes. W/O Pickering HIPEs are stabilized by using sufficient modified GO flakes even at a low concentration (0.2 mg/mL) because of the huge specific surface area GO. The poly-Pickering HIPEs have a closed cell structure. The modified GO with a higher concentration used to stabilize HIPEs leads to the macroporous polymers having a smaller void size and a narrower size distribution. Three-dimensional macroporous chemically modified graphene (CMG) monoliths with a large specific surface area of up to 490 m2/g are successfully fabricated after removing the porous polymer substrates. The microporous structure of CMGs may be induced by the decomposition of CTAB molecules adsorbed on the GO’s surface.(2) Double-chain surfactant dihexadecyldimethylammonium bromide (DHDAB) can improve the hydrophobicity of GO flakes more efficiently, which cause GO flakes in a wide range of modification can be used to stabilize W/O Pickering HIPEs. The pore size and morphology of poly-Pickering HIPEs can be tuned by different degree of modification and water-oil rations. At higher surfactant concentrations, GO flakes are coated with bilayers of DHDAB molecules, resulting in a positive charge on GO. Interestingly, porous polymers with open-cell structures can be prepared by using highly modified GO. Moreover, we make Ag nanoparticles deposit on the pore surface of poly-Pickering HIPE by one-step method. Consequently, Ag nanoparticles enhance the Raman signal of GO on the pores’ surface.